Baker Mobile LiDAR

Identifying the Need for Mobile LiDAR

2012-02-13T09:39:00.000-06:00

In my latest LiDAR News article, I take a stab at how we Identify the Need for Mobile LiDAR for a given project. I briefly discuss 5 key characteristics to evaluate the use of the technology:

Level of Detail
Schedule
Safety
Access
Security

Although there are other circumstances which influence a decision, these key elements are the primary drivers in the process.

Cheers!

Stephen

Data Fusion: Mobile and Aerial LiDAR

2011-11-14T11:17:00.002-06:00

Over the weekend, Baker's latest article on LiDAR News was published. The topic is "Data Fusion" - Mobile and Aerial LiDAR as well as traditional surveying. In an earlier posting on the blog, I wrote about Knowing your Limitations - whether they're environmental, scale or technological. Often, one tool or technology does not completely solve a problem. By fusing data from multiple sources, we're able to complete the picture.

Below are the images from the article in more detail:

The image above presents the fusion of Aerial LiDAR (red) and Mobile LiDAR (white). The tops of structures, including poles and push braces, are completely saturated with LiDAR points while the rail corridor (immediately adjacent to the buildings) contains dense information.

The image above depicts the fusion of Mobile LiDAR and Traditional Surveying (Aerial LiDAR points removed for clarity). The LiDAR data was supplemented outside of the Mobile LiDAR corridor to locate utilities, property boundaries and other features not captured by Aerial means within the larger corridor.

As the closing states, the information represented in surveying/engineering drawings can be captured in a number of ways. Having an array of tools at your disposal can dramatically impact how you approach an assignment. The integration of outputs from various technologies can provide a different perspective.

Cheers!
Stephen

Mobile LiDAR: Law #13

2011-09-21T13:36:00.001-05:00

Mobile LiDAR is not all fun and games, but it does feel like it some days.

What could be more enjoyable than mounting a couple lasers on top of a 4 wheel drive SUV, cruising at highway speeds, shooting it at everything that the eye can see and calling it work? It’s a career that would have Tim “The Toolman” Taylor stand-up and say “more power, ARGH, ARGH, ARGH”, (although our system is manufactured by Optech, not Binford). How about adapting it to fit a boat, an all-terrain vehicle or a hi-rail? Now we’re talking… it’s like a sophisticated NextGen video game that would make my twelve year old son envious. In this context, it’s easy to forget that the laser is a highly advanced optical imaging system, operated by experienced survey technicians, which is used to collect vast amounts of precision data for a multitude of real world applications. If engineered correctly, a Mobile LiDAR unit will serve as a cost-effective survey grade solution that can be used to generate high quality project deliverables in a surprisingly quick timeframe. This is where the fun stops and the real work starts.

Baker's Mobile LiDAR unit is mounted on a Hi-Rail equipped truck
to perform a collection on a railroad corridor.

The implementation of a mobile LiDAR project can often be a rigorous undertaking, sometimes involving hurdles that would challenge the greatest of the world's Olympic sprinters. First and foremost is the sale. You would think that the system’s efficiency, accuracy and safety features would enable the technology to sell itself, but the resistance to change innate in economic buyers sometimes results in the need for the “hard sell”.

There’s hardware and software configuration, system calibration, survey control, and pre and post processing procedures that must be painstakingly followed to ensure a quality data output. And let’s not forget the logistics of scheduling… Mother Nature is not always the most forgiving of patrons. Mobile LiDAR data collections are serious business. However, if managed properly, it might just give four wheeling on a muddy summer day in the bayou a proverbial run for its money in the fun and games category.

Got LiDAR?

Cheers!

David

David Fekete is GIT Operations Manager for our Harrisburg, PA office. He joins other manager's within Baker's GIT Service Area as a guest author to the blog. In the coming weeks, additional guest authors will continue providing content from a different perspective.

Mobile LiDAR: Law #8

2011-09-12T22:12:00.000-05:00

Today’s best practices will be tomorrow’s old habits.

We hear a lot about “Best Practices;” but first off, let me say that I’m not a fan. Context, culture, and regulations dictate our practices. What equals success in one market may not work in another. And not all locations are created equal. So, for most purposes the terms, “good practices”, “suitable practices” or “useful practices” make more sense to me.

So what makes a good/suitable/useful practice…a so-called best practice? Since bottom-line is critical in business, any best practice must be measurable and must contribute to the bottom line. If a practice isn’t cost effective, it isn’t going to happen. Systems must support change in practice, and processes must allow for interaction between the users and the implementers.

Being a relatively new technology, change in Mobile LiDAR is rapid. So while the technology is cutting edge, the processes for developing our LiDAR projects ought to be our old habits. Today, they represent good/suitable/useful practices…the so-called best practice.

Plan, Plan, Plan – You’ve heard about GIGO: Garbage in Garbage out. It’s as true in Mobile LiDAR as in any other project type. To avoid GIGO, getting ready for the project is as important as the actual work that follows. (See Project Planning - GPS post) Identify all state and other relevant agency specifications and project coordinate systems. Develop a mission plan for data collection. Perform system calibration, reconnoiter geodetic control for SBET processing and establish necessary survey control necessary post processing of LiDAR data.
Get the Data – Set up base stations on geodetic control. Collect the GPS and Mobile LiDAR data . Perform preliminary data processing, including data extractions and SBET creation; and finally, generate the point-cloud.
Process Data – Transform, tile and classify point data. Produce intensity images. Make various extractions.
Develop the Product(s) – Digital Elevation Models (DEM's), Triangulated Irregular Networks (TIN's), contours, breaklines and detailed planimetrics. Generate tile and project level-set metadata.
QA/QC – Don’t treat QA/QC as a final step. Incorporate it in every instance.

You’ll definitely get the best product with these best practices.

Cheers!

Donna

Donna Kristaponis is GIT Operations Manager for our Reno, NV office. She and other managers within Baker's GIT Service Area will be providing guest postings over the coming weeks.

Re-purposing the Cloud

2011-09-01T07:45:00.001-05:00

Sustainability is a hot topic these days. The high-density point-cloud generated from a single Mobile LiDAR collection is a virtual poster-child for sustainable solutions. A key advantage to utilizing Mobile LiDAR on most projects is the ability to re-purpose the data for a myriad of uses or downstream projects. Rarely, if ever, do we get the opportunity to fully capitalize on the wealth of captured information on a single project. But if you’re an organization with diverse needs or numerous departmental groups, such as a local municipality, the ability to re-purpose the point-cloud for multiple projects creates exponential cost savings each time the data is exploited.

Land Development is another great example. We recently deployed our system to capture the as-built condition of a business and technology center in Chesapeake, VA. The center is relatively new, so there are still a number of vacant parcels that have yet to be developed. Scanning the entire complex took about an hour; but from that single collection, the developers not only obtain an accurate as-built of the site, but can also re-use the data to:

Develop land-use classification models;
Create animated fly through’s or 3D renderings to entice prospective tenants;
Quickly assemble to-scale 3D architectural renderings for the design/review process; or
Analyze and assess the enforcement of local codes/ordinances relating to sight-lines or green space.

The fascinating part is these were just the first things that came to mind. I think our motto sums it up pretty well. Unlimited Data…Infinite Possibilities!

Cheers!
Jonathan

Jonathan Soulen is GIT Operations Manager for our Virginia Beach, VA office. He and other managers within Baker's GIT Service Area will be providing guest postings over the coming weeks.

SAE 2011 Autonomous Vehicle Symposium

2011-08-12T13:41:00.000-05:00

Baker’s resident LiDAR Scientist, Dr. Srinivasan “Srini” Dharmapuri, was a featured presenter at the Society of Automotive Engineers (SAE) 2011 Autonomous Vehicle Symposium, held at Carnegie Mellon University (Pittsburgh, PA) on 8/10/11. The symposium showcased smaller and more focused discussions on innovative drive assist and autonomous vehicle technologies in transportation, agriculture resource management, construction and mining. Srini’s presentation conveyed the advantages and uses of Mobile LiDAR technology, and highlighted several case studies performed by Baker in the Transportation arena , including roadway design, rail transit, and bridges. The diverse group of international attendees included prominent individuals from the public and private sectors, as well as academia.

As Baker's resident LiDAR Scientist, Dr. Srini is responsible for application development, QA/QC methodologies, technical writing, improving processing efficiency and other related LiDAR (static, mobile and aerial) activities. As mentioned in an earlier posting, Srini is the Vice Chair of the ASPRS Mobile Mapping Committee. Perhaps he can provide an update on the committee's activities in the near future.

If you have a topic for Srini to write about, please leave it as a comment and we'll include it the Ask the Doctor series.

Cheers!

Stephen

Mobile LiDAR Interview with Aaron Morris

2011-07-28T13:54:00.000-05:00

During the 2011 ESRI International User Conference, Baker's Aaron Morris took a few moments away from our booth to be interviewed by VerySpatial. Aaron provides a background on Mobile LiDAR and highlights some of our recent projects. The podcast is now available online or through iTunes.

Thank you to Jesse and the rest of the crew at VerySpatial for the opportunity for us to share Mobile LiDAR with their listeners.

Cheers!
Stephen

Mobile LiDAR: Positioning Systems

2011-07-22T15:37:00.000-05:00

In my most recent article for LiDAR News, I provide an overview of Positioning Systems for Mobile LiDAR. It is a little more in depth than a blog posting I prepared back in 2009 titled Measuring Systems Part 1 - Positioning.

Mobile LiDAR is a system comprised of various components that are connected to provide a solution.

My belief is that the Position and Orientation System (POS) used to develop the Smoothed Best Estimate of Trajectory (SBET) is the distinguishing factor between available Mobile LiDAR systems. The ability to accurately position the vehicle has downstream advantages for the initial LiDAR processing and subsequent control adjustment.

Cheers!
Stephen

Mobile LiDAR Blog goes Mobile

2011-07-16T14:03:00.000-05:00

Following up on the recent redesign to the blog, I applied a mobile template so it can easily be viewed on your smart phone or other mobile device. Since it seems we're all on the go these days, it will be easier to check in to see the latest postings.

Sample of the Mobile Template

In addition, I've included the QR code that will take you directly to the site. After having a Blackberry for nearly a decade, I'm still getting used to my iPhone keyboard and the code comes in handy.

Let me know what you think of the recent changes.

Cheers!
Stephen

Baker's Dozen: 13 Laws of Mobile LiDAR

2011-06-30T08:56:00.001-05:00

A little over a month ago, our Ridgeland office hosted a visit by Baker's CEO, Brad Mallory. During a presentation of projects our Transportation group was working on throughout Mississippi, it was quickly observed that several of the slides had 13 projects listed - a Baker's dozen.

From that meeting, an idea was born to develop "Baker's Dozen: 13 Laws of Mobile LiDAR." These Laws were developed after much thought and consideration. In coming posts, I will explain each of the Laws in detail providing further explanation.

Without further ado, I unveil the Baker's Dozen: 13 Laws of Mobile LiDAR (also currently being chiseled on a slab of granite):

Too much is better than not enough.
Sometimes more is just more, not better.
Hard drives are cheap, time isn’t.
Consistency counts; stop guessing.
When someone wants “full planimetrics,” they really don’t.
The stated laser range is X’, but the lasers are only capturing data to Y’; and Y is definitely less than X, yet nobody can tell you what Y is…
The data you capture is only as good as the applied control.
Today’s best practices will be tomorrow’s old habits.
Field vs. office time ratios are pipe dreams.
Mobile LiDAR systems are not created equal, and neither are the operations behind them.
Off-the-shelf processing software will only do 50% of what you need it to do.
When the system encounters issues, take a breath and reboot.
Mobile LiDAR is not all fun and games, but it does feel like it some days.

Feel free to let me know what you think. Perhaps we can have a committee gathered to debate them or formalize some agreement.

Cheers!
Stephen

Riding the Rails

2011-06-27T16:25:00.000-05:00

Back in March, Baker performed a Mobile LiDAR collection of a high speed rail corridor encompassing approximately 240 miles (opposing tracks along the same corridor). Now that the primary products have been delivered, I took an opportunity to create several screen captures of the collection. The two images below present different views of the same section of track.

Facing northwesterly, the screen capture clearly depicts the ability to capture a number of elements beyond the rail features. The handiwork of local "artists" is evident thanks to the intensity returns from the system.

An opposite view from the image above shows the extent of overhead electric distribution, communication and fiber optic utilities. Also present are supporting guy anchors, a single mile post and other features necessary to develop engineering design drawings.

The detail of information captured in a single collection is quite impressive. In addition to the planimetric feature extractions and track geometries, Baker developed a digital elevation model following constraint of the Mobile LiDAR collection.

Let me know what you think.
Stephen

Complexities of a Mobile LiDAR Survey

2011-06-15T16:58:00.000-05:00

A few weeks ago, my fifth article for LiDAR News was published. The article, titled "Complexities of an Urban Survey," discussed our recent collection of Charleston, WV. The collection encompassed an incredibly varied urban and rural environment along 350 miles of public rights of way (collected in opposing directions). Through project planning, we attempted to mitigate or minimize the known challenges we were going to face.

The images presented in the article are shown below:

As the article states, we established control target layout for a local survey firm. Above is a representation of a Google Earth KMZ depicting the control point layout.

Each SBET (sometimes a few a day due to weather) were exported to a Google Earth KMZ to perform cursory review of status.

Our Mobile LiDAR crew and Program Manager, Aaron Morris, provided an "Open House" to city staff and the media.

My next article for LiDAR News will be on the Position and Orientation System. Should you have a topic to consider, leave me a comment.

Cheers!

Stephen

ASPRS - Mobile Mapping Committee

2011-05-06T10:00:00.001-05:00

The ASPRS Mobile Mapping committee meeting took place on May 2^nd at ASPRS's Annual Conference held in Milwaukee, Wisconsin. Dr. Craig Glennie from the University of Houston, Texas is the new Chair and Dr. Srini Dharmapuri, LiDAR Scientist at Baker is the Vice Chair.

The meeting began with a discussion of the some of the significant activities in the mobile mapping community over the last year, including:

The release of mobile laser scanning specifications by Caltrans
The currently pending TRB contract to develop guidelines for mobile LiDAR in transportation applications
The formation of the GTMA (Geospatial Transportation Mapping Association)

After this brief summary, it was decided that the committee should concentrate on the formation of a best practices and guidelines document, with the goal of having an initial draft prepared for ASPRS 2012. To this end, a proposed framework for this document was presented (and given in the attached word file).

The Mobile Mapping committee is looking for volunteers to assemble “best practices document” and interested parties may get in touch with Dr. Craig Glennie and Dr.Srini Dharmapuri.

Good luck to Craig and Srini as they lead the endeavor to establish standards and best practices for the Mobile Mapping industry.

Click to download the Mobile Mapping Committee Presentation.

Cheers!
Stephen

No Place for Survey Crews

2011-04-21T12:15:00.001-05:00

Earlier this year, we were tasked to perform a Mobile LiDAR collection of an Interstate tunnel (2 lanes in each direction - measuring 0.8 miles in length). The tunnel is in a heavily trafficked urban corridor where closures required by traditional surveying, even in the early morning hours, were completely out of the question.

Due to the constant, unrelenting traffic, we performed the collection shortly after midnight. We collected each of the 4 travel lanes at or slightly below posted speed limits - slowing down or speeding up to minimize laser shadows from other vehicles. Following the collection, our LiDAR processing staff and Applied Technology Group produced the final products.

First, our LiDAR processing staff adjusted the passes to ensure coincidence. Then they made quick work of removing other vehicles from the point cloud. Then, they turned over the tiled point clouds for modeling.

An image of the point cloud with vehicles removed, but tractor trailer model added. Notice the pothole in the bottom left hand corner of the image.

Our Applied Technology Group utilized the cleaned point cloud to create a rendering of the tunnel in MicroStation.

In the article I wrote for LiDAR News last week I made the statement "if you can’t see it, the system isn’t measuring it." The below image is directly disputing that statement - which I don't quite mind in this case.

The image shows a cross-section of the tunnel. Notice the arc above the "box" tunnel. The arc represents returns from the actual tunnel ceiling (extent of bore) that were measured through small (1") joints in the false ceiling.

Perhaps what is most fascinating to me is not that the system captured this information, but how it will be exploited by our client.

Cheers!
Stephen

Knowing your Limitations

2011-04-18T11:05:00.000-05:00

I have recently prepared another article for LiDAR News titled Knowing your Limitations. Understanding what a technology does not do is equally, if not more, important than understanding what it does do. Where those limitations can affect the successful outcome of a project, other methods, tools or techniques are needed to compensate. The article addresses some of the larger topics. In upcoming posts, I'll provide additional items to consider when pursuing a Mobile LiDAR project.

The images presented in the article are shown below with captions:

Manholes: In a span of 40' along a roadway, there are 6 manholes and two water valves.

Grass on Bare-Earth/DEM: A random non-Federal levee shows the difficulty dense vegetation adds to determine bare earth along the bank.

Obscured Areas: The area behind two parallel parked cars is obscured in comparison to the open area between them. The shape of the voids depicted, represents the orientation of the lasers and varies based upon heading.

As always, please let me know if there are any topics you would like to see discussed.

Cheers!

Stephen

Defining Accuracies

2011-03-04T15:54:00.000-06:00

I have written a third article for LiDAR News which addresses accuracies of Mobile LiDAR information. It may be accessed through this link.

The images in the article illustrate how we constrain our collections to ground control, much in the same was as aerotriangulation (AT) in Photogrammetry.

The table shown below (and included in the article) illustrates the difference between our check points (labeled Control) and the LiDAR point elevation at the corresponding locations. This methodology is used to calculate the accuracy per the National Standards for Spatial Data Accuracy.

Should you have a topic for discussion, please leave as a comment.

Thanks,

Stephen

Lots of Dots

2011-02-04T13:11:00.000-06:00

The other day, a friend and business acquaintance addressed a letter to me as "Mr. Lots of Dots." I thought it was fitting given that my professional life is all about dots, dots that we measure and dots showing where we've been.

That evening as I was reading my son his favorite story - There's a Map on My Lap* - the words took on a entirely new meaning. Even though I've probably read the book 200 times, one particular rhyme stood out:

"Dot maps, like this one,
are covered with dots.
Some have a few dots,
but some others have lots."

Last week, our Mobile LiDAR vehicle surpassed 40,000 miles (several more miles if you include it taking a ride on a barge). With each new mobilization as we're collecting more dots, we're also adding new dots for the places we've been. If it wasn't for the wrap we have on the truck, I would have one of those sticker maps you see on the back of RV's because,

"You can always use maps.
They will help you in knowing
where you have been
and just where...
...you are going."

If you are a geospatial professional and have children (or a wife that doesn't understand what it is you really do), the book There's a Map on My Lap is a great way of explaining what you do. I've bought copies for several friends that have become new parents. Also, it makes a great read for younger students for GIS Day.

Enjoy!

Stephen

Mobile LiDAR: Projects at a Glance

2011-02-03T17:02:00.000-06:00

My second article for LiDAR News is now available. It may be accessed through this link.

The image in the article is shown below. It is an intersection of SR30A in Panama City, FL - collected May 2010. You can clearly make out the extraction of pavement markings, sidewalks, utilities, pavement edges and other features.

Should you have a topic for discussion, please leave as a comment.

Thanks,

Stephen

Dick Henderson Animation

2011-01-26T08:45:00.018-06:00

I uploaded an animation of our Dick Henderson Bridge collection to YouTube some time ago. The short video shows the combination of the point cloud information with derived planimetrics of the underneath structure and piers.

I compiled the animation using Pointools with a little transition editing afterwards. I've been using the software for some time now to generate these animations and to create the screen captures shown in this blog.

Cheers!
Stephen

Corridor Mapping

2011-01-24T18:39:00.000-06:00

Recently we were awarded a contract to perform mapping along a 108 mile corridor through central Louisiana. Our Mobile LiDAR crew completed the data collection over two days - each day collecting 2 passes in opposing directions. In order to illustrate the ground covered, I exported the vehicle trajectory to a Google Earth KML file (see below).

Along the corridor, there were several areas where the alignment was uncertain. Due to the ease of acquiring additional areas, our crew made additional passes to completely capture the necessary information. The image below demonstrates how our crew made multiple passes along the new US 167 alignment as well as the old alignment.

The Size of Data:

Covering all that ground is bound to create a substantial amount of data. During the collection, our system acquired 55,727 images. In addition, we processed 170.3 GB of LAS files.

My colleagues and I are contemplating how many points were collected over that time period. Would anybody venture a guess? Feel free to post your guess! Should I get a number of guesses, I may post the actual number.

Cheers!
Stephen

Mobile LiDAR & GIS: Background of a Service Provider

2011-01-12T09:52:00.000-06:00

I have the pleasure of being a contributing author to LiDAR News - a new electronic newsletter by Spatial Media. My specific focus will be Mobile LiDAR and GIS - with a host of other contributers addressing Aerial LiDAR, Static Scanning and Processing.

My first article is now available and is a basic introduction of things to come. It may be accessed through this link. I will be collaborating with other authors when appropriate to address processing, animation and sensor fusion.

Should you have a topic for discussion, please leave as a comment.

Thanks.

Coloring the Cloud

2010-12-14T20:33:00.002-06:00

Nearly a year ago, I wrote a posting titled Measurement Systems Part 2 - Lasers and Cameras. In it, I first presented how the combination of the Mobile LiDAR data and imagery from the system's on board cameras are combined to create colorized point clouds. Having a broad static scanning background, I often went through great lengths to recapture pictures to improve the colorized cloud. We face similar challenges with the Mobile LiDAR system. With proper planning, patient operators, creative scheduling and a little bit of luck, the results can be impressive.

Below is an image captured from one of the cameras positioned on the rear of the platform and facing backward. As you can see, the trees cast shadows across the road surface. Collecting multiple passes down the road would create additional shadows at different angles.

The image below is the colorized point cloud. We colorized one pass (two strips) down this rural road. The cross hatch pattern created by the two sensors is clearly visible at the bottom of the image.

The below image clearly shows the concrete/asphalt transition, pavement markings and other roadway characteristics.

Wikipedia states: "The adage "A picture is worth a thousand words" refers to the idea that a complex idea can be conveyed with just a single still image. It also aptly characterizes one of the main goals of visualization, namely making it possible to absorb large amounts of data quickly." I'm curious how a colorized point cloud would be described.

In the coming posts, I will present how else we are utilizing the images captured by our Mobile LiDAR system.

Enjoy!

Stephen

Mobile LiDAR Podcast

2010-11-08T09:55:00.021-06:00

Recently, I had the pleasure of being interviewed by Matthew DeMerritt of Esri. The interview was part of Esri's Speaker Series and is available online through their website or Apple's iTunes as a Podcast.

Titled Streetview Lidar, the interview briefly explains Mobile LiDAR and how it can compliment Aerial LiDAR.

West Virginia - Preliminary Information

2010-11-04T08:33:00.013-05:00

As we finish the final products for the bridge we collected a couple weeks ago, I want to share some of the preliminary information. As mentioned in the posting titled "On the Water with the Baker Navy", we performed a collection with the unit on a barge (SBET shown below in blue) and a collection from the vehicle (SBET shown below in red). Since we utilized the same GPS base, the collections were seamlessly integrated and adjusted.

We exported both SBET's to a Google Earth KMZ file to visualize the vehicle trajectory. An interesting feature of Google Earth is the Elevation Profile tool. The below image shows the land collection SBET and elevation profile. The profile pulls the Z value from the KMZ file - rather than clamping the information to the ground. Notice that our Mobile LiDAR crew made 4 passes over the bridge. The position of the red arrow represents the vertical line in the profile - showing elevation, slope and distance from start along the drive.

Next, the preliminary LAS data was processed. The two images below show the intensity values from the LAS data from both collections. No adjustment was performed up to this point.

Since this is unadjusted LAS data, there is "noise" in the data due to inaccuracies in the SBET - primarily caused by loss of GPS. Using the ground control established using the Trimble S6 reflectorless total station we carry on-board the vehicle, the point cloud was adjusted to be coincident and to meet the localized coordinate system for the project.

Mississippi River Levee

2010-11-03T14:37:00.001-05:00

Given my recent travels and work assignments, it's been hard to find time to update Baker's Mobile LiDAR blog with new content. Aaron stepped in a couple weeks ago for the Revisiting Yazoo post. And now that products are being finalized for some recent collections, new postings will be forthcoming. In the meantime, one of our technicians compiled a brief fly through of the Mississippi River Levee collection.

The below animation shows an intensity and colorized point cloud of a two mile stretch of levee along the east bank of the Mississippi River outside Baton Rouge. Areas not colorized do not appear in the photographs taken by the on-board cameras.

Some of the challenges we face in colorizing point clouds include:

Changes in sun angle during collection
Orientation of the vehicle with respect to the sun (vehicle shadow in images)
Saturation of the upper portions of tree canopies
Vehicles and other extraneous objects in the images

Again, project planning comes into the "picture." If a colorized point cloud of a roadway corridor is required, it would prove more wise to perform two shorter collections during off-peak hours (perhaps a Saturday and Sunday morning) to improve the final product.

Revisiting Yazoo

2010-10-19T20:05:00.001-05:00

With our busy schedules, and travels across the country, it’s easy to get caught up in the hoopla for the next scanning project, but it’s also important to take a moment and reflect on where we’ve been - or what we've seen and captured.

With over 56 scanning projects under our belt, which span the country from coast-to-coast, sometimes it takes a visual/audible cue to bring a particular collection back to the forefront of the mind. Such was the case last week while driving through the plains of Kansas and Nebraska, when I heard a radio advertisement for the new season of the Discovery Channel’s Storm Chasers television series.

It’s hard to believe, but it’s been almost 6 months since we scanned the aftermath of a devastating EF4 tornado that tore through Yazoo City, MS, on its epic 149 mile path through two states. Our long-time followers may remember the original blog postings back in May, but in case you want to refresh your memory, or if you’re a new follower, Part 1, Part 2 & Part 3

The LiDAR data, along with the thousands of still images we captured in the aftermath, really tell the story of how destructive a tornado can be; but to really get a feel for the storm as it happened, make sure you tune into Wednesday (October 20^th) night's episode (10:00 pm Eastern), or the myriad of re-broadcasts throughout the week, to watch video footage from the chase vehicle's perspective.

If you’re a fan of the show, you’ll recognize the TVN “Dominator” pictured here behind our system, along with the numerous support/chase vehicles that capture the show's footage.

- Aaron

On the Water with the Baker Navy

2010-10-14T19:47:00.001-05:00

Sometimes, a project requires a different approach than what has been performed in the past. We were presented with one such project for a bridge in West Virginia. Capturing the structure underneath presented a challenge that could not be accomplished using traditional means - total station or static scanning. Therefore, we utilized a barge to move our system around underneath the structure.

Having not been on-site, but in contact with the crew throughout the day, I had no idea the barge was so large. It was in service on the project already and we merely had to drive the Suburban up onto it - no need to dismantle the system and perform additional system calibration. I was quite surprised to see the size when I received the pictures.

Our crew could take it easy during the collection. The barge operator performed a ballet of maneuvers beneath the bridge and around the pilings to inundate the support structure. If you recall from our Measuring Systems posting, there should be a DMI cable running down the side of the truck.

Since we obviously weren't going to be driving around on the barge, there was no need for the DMI, so we utilized an alternate collection methodology to account for the barge's movement, as opposed to wheel revolutions. This also meant that we could maximize our time onsite, by stationing one crew member with the system, while the other used the Trimble S6 total-station that we carry on the vehicle to measure identifiable targets on the bridge to adjust the point clouds together.

Following the collection on the barge, the crew attached the DMI and collected the topside of the bridge. The entire collection, including control, was completed in a single day. I can't wait to see the results, which I will be blogging about soon enough.

Modeling Bridges from Mobile LiDAR Information

2010-10-01T08:21:00.000-05:00

I often tell people that the products derived from Mobile LiDAR data are only limited by one's imagination and willingness to push the envelope. On that premise, we recently performed work on an interstate including overpasses and ramps. In addition to the typical MicroStation planimetrics and DTM, Baker's Applied Technology (AT) group was enlisted to prepare models of collected bridges. While looking at the progression of the modeling, keep in mind that the information was collected at posted speed limits.

Below is a simple slice of the Mobile LIDAR point cloud representing the North/South bound lanes of travel. I quickly added height clearances which I used to calculate an approximate slope. At each of the bridges, we created subsets of the point cloud to minimize processing during the modeling phase.

From the subset point cloud, our AT staff began modeling the environment. Presented below is a wire-frame of the modeled solids (modeling involves developing a mathematical representation of 3-dimensional features). The ground is represented as a Triangulated Irregular Network (TIN). In a wire-frame, the outlines of the features are depicted with the point cloud still visible.

After the wire-frame, a hidden line model is presented below. Basically the shapes and surfaces shown in the wire-frame are filled. The solids depicted have no texture, but the model begins to take shape.

Then a draft of the model is prepared for visual inspection. The impact of grass in the median is clearly visible. Since we started without the luxury of a classified point cloud, our AT staff cleaned the surface using MicroStation InRoads (can also be completed in GeoPak). Obviously starting with a classified LAS containing bare-earth and vegetation points, would have saved a little time for our modelers.

Perhaps the coolest image, in my opinion, is the Ambient Occlusion (AO)image shown below. The software we utilize provides the ability to create shadows, define sun angles and change perspective depending on time of day. I also like that it shows an immense amount of detail on the guardrails and other features.

By adding vehicles to the model, it provides a sense of scale and depth. The vehicles in the AO image are used to determine the shadows they cast on the model as well.

Finally, textures and colors are applied to modeled features. The shadows cast are incredibly detailed - notice the guardrail and pillars on the right-hand side. The next step is to add cars, collected roadway signs and other ancillary information - perhaps our team can throw a model of the Mobile LiDAR unit in there rolling down the interstate.

For more information on Baker's Applied Technology and the services they provide, please contact:

Alan B. Palmieri

Senior Designer

3D Design and Visualization

Michael Baker Jr. Inc.

412-269-2987

www.bakervr.com

Alan and the rest of the group have exceeded our expectations time and time again. Perhaps down the road I'll share more of their superior work modeling Mobile LiDAR data.

Controlling the Cloud

2010-09-15T15:52:00.000-05:00

Mobile LiDAR data on it's own is not what I would classify as "survey accurate" - being accurate enough to defend (sign and seal) for engineering design or similar services. The same can be said for any survey instrument because the result depends entirely on the standard of care applied during collection and subsequent processing. I'm going to provide the 10,000 foot perspective on how we achieve survey accuracies of Mobile LiDAR derived products.

First, let's revisit the blog on Project Planning. In that posting, I discuss how the GPS solutions we achieve differs throughout the day due to the constant motion of the constellation. Therefore, if we were to drive the same area twice, we would very likely get different results. We utilize a process much like Aerotriangulation in Photogrammetry with respect to our individual strips. The process employs ground control points (measured to a higher level of accuracy or certainty) to tie overlapping strips together.

In the image below, we've color coded the different strips and are depicting the Z/Elevation axis. The eight strips present a "thickness" both above and below the respective control point. In this example, the variance between high and low is about 0.25' - or 0.13' above and 0.13' below the control point.

Using tie-lines, our processing staff links the point cloud to the ground control. The process can also be applied between an adjusted and unadjusted point cloud using "LiDAR identifiable" points (similar to a cloud to cloud registration applied in static scanning). Below is a screen capture following adjustment. The variance in the cloud is approximately 0.02' - resulting in a highly effective adjustment and providing the foundation for deriving final products.

No matter what we would like to believe, surveying is not absolute. There are errors, whether systematic or random, in each measurement. Where the differentiation lies, is in the ability to minimize or effectively eliminate those errors through field collection best practices, processing algorithms and a general appreciation of the work being performed.

The Year in Review

2010-09-13T12:03:00.000-05:00

It's hard to believe, but yesterday marks the 1st Anniversary of the installation of Baker's LYNX Mobile LiDAR system in Beaver, PA. Following the build out of the storage drawers and vehicle wrap, we spent the day installing and calibrating the system in addition to running inside to catch up on college football scores. (Revisit our first blog - Day 1: System Install)

Inside the Numbers:
Over the past year, Baker staff have exhibited or presented at a dozen national conferences, more than 30 regional conferences and countless Baker offices, local meetings and user groups. We have written more than 30 blogs which has attracted over 3,000 visitors and nearly 10,000 page views. Our staff continues to add content and videos on an increasing array of topics.

The Mobile LiDAR unit has performed collections from Pennsylvania on south to Florida; we've collected the Atlantic Ocean in Virgina to the Pacific Ocean in California. Our collection crew has put more than 30,000 miles on the vehicle and collected about 50 terabytes of data.

Yes, I'm reading instructions - contrary to every other time in history.

We've performed collections along levees, neighborhoods, highways, runways, railways, rivers and beaches. During all of this, I have been the only person who has managed to get the vehicle stuck - once. And a few months ago, we added the auxiliary vehicle to our fleet increasing our capabilities.

Our Mobile LiDAR team continues to race forward and push the technology. It is exciting to be a part of the team and work with such dedicated professionals. I'm certainly looking forward to year 2 and what it has in store for us.

Thank you to all that have made this possible.

Baker at AREMA

2010-08-25T08:50:00.005-05:00

Michael Baker Jr., Inc. will be exhibiting at the upcoming 2010 Annual Conference of the American Railway Engineering and Maintenance-of-way Association (AREMA). The conference is being held at Hilton Orlando from August 29th through September 1st. Look for Baker representatives at Booth #616.

Upcoming Workshop

2010-08-23T07:52:00.000-05:00

On Wednesday, August 25th, Stephen Clancy will be presenting a 3 hour workshop titled "Mobile LiDAR: An Overview of Surveying's New Tool" at the 55th Annual FSMS Conference in Naples, FL.

Stephen will present Mobile LiDAR basic concepts, collection, preliminary processing and final deliverables.

Portions of the course will be made available through the blog beginning the first week in September.

Project Planning - GPS

2010-08-17T20:49:00.001-05:00

Expanding upon an earlier post - Measuring Systems Part 1 - Positioning, I would like to talk about planning. Perhaps the most significant factor in a successful collection is the GPS constellation. Since the vehicle encounters many obstructions to the sky - trees, buildings, signs and other structures to name a few - it is desirous to collect when there is the highest likelihood of satellite visibility. Sometimes this means our Mobile LiDAR crew is collecting in the early morning hours.

Utilizing simple planning software and an updated GPS almanac, we're able to input our project latitude and longitude coordinates to determine the times that we should be collecting - and when the crew should be doing something else.

The image above shows a 24-hour period for New Orleans, LA. The number of visible satellites is but one thing we look at. In addition, we look at the Position Dilution of Precision (PDOP) - a measure of strength of the geometry of the satellites. Typically, the number of satellites has a direct correlation to PDOP (take a look at the dip in satellites around 08:30 above with the spike at the same time below). However, it does not necessarily mean that you will have a high PDOP if you have fewer satellites if the geometry of those satellites is strong - evenly distributed in the sky.

The successful completion of any project is planning. The planning we perform for our Mobile LiDAR collections occur at many levels, each of which can vastly influence the results.

How Well Did You Do?

2010-08-09T11:24:00.002-05:00

Following up on the Name That Car Contest, I've compiled the cars that were depicted in the point clouds. Craig is the winner with 4 correct. Some of these proved a little more difficult than others and for good reason. Thanks to all of you who participated - even submitting into Friday morning. I've attached some of the images.

#1: Ford Escape - multiple people identifying it as a Mazda Tribute (same car). I had the luxury of a photo of the front - the blue oval is unmistakable.

#2: Acura MDX

#3: Honda Accord - Going old school with the old body style.

#4: Audi A3 - The front grill gives it away.

#5: Ford Econoline: No body missed this one.

#6: VW Beetle: Again, no body missed this one.

#7: Chevrolet Aveo: The one nobody got.

Something that threw me regarding #7 is how the plastic bumpers appear different than the metal body in the point cloud due to the various intensities.

Time is running out...

2010-08-03T21:33:00.001-05:00

Tomorrow at 5 PM Central, the Name that Car Contest ends. No one has identified all of the cars correctly. So, there is still time. Email me your picks.

Good Luck!
Stephen

Meet the Crew

2010-07-29T06:58:00.014-05:00

All too often, the people doing the lion's share of the work are often those least recognized. Therefore, let me take this opportunity to introduce you to two gentlemen that are a huge part of what is making our Mobile LiDAR activities so successful. Pictured below are Richard Scialoia (left) and Justin Thornton (right), acting as Mobile LiDAR Surveyor and LiDAR Operator, respectively. They are the individuals tasked with successfully executing our Mobile LiDAR collections and often help with adjusting procedures or making recommendations.

Justin has B.S. and M.S. degrees in Geography and Geographic Information Systems from Florida State University. He has been with the system since the installation and has been instrumental in the success to date. Whereas, Rich joined Baker in April to act as Surveyor, Driver, Secondary Operator, Preliminary Data Processor...... He has extensive project management experience which includes Aerial LiDAR control survey support. They are two uniquely qualified individuals that have done a superior job representing Baker and the Mobile LiDAR Team.

Thank you Justin and Rich for continuing to work hard and perform superior work!

Reminder to Enter the Contest

2010-07-28T17:00:00.003-05:00

Don't forget to enter the Name that Car Contest. There is one week left before the entries are reviewed and the winner determined. I can not possibly put into words how great these Baker travel mugs are. Don't miss out!

Gotta Love Intensities

2010-07-26T08:09:00.018-05:00

While compiling images for the "Name that Car Contest", I created a few more interesting screen captures of vehicles. What they're delivering may be a question if it weren't for the intensity values from the LiDAR data. Each of these images were derived from a single pass of our vehicle down the streets of Morgantown, WV.

I hope you find this as interesting as I do...

Ask the Doctor

2010-07-23T07:41:00.000-05:00

We would like to welcome a new member to our LiDAR team. Dr. Srinivasan “Srini” Dharmapuri is a 25 year veteran of the geospatial sciences, and has extensive, wide-ranging experience within the Geospatial industry; most notably with LiDAR, Photogrammetry, and GIS. He has worked in both the private and public sectors, as well as internationally. In addition to his educational achievements, Master’s of Science (Physics), Master’s of Technology (Remote Sensing), and Doctorate (Satellite Photogrammetry), Srini is also an ASPRS Certified Photogrammetrist and licensed Photogrammetric Surveyor in South Carolina and Virginia, as well as a Certified GIS Professional.

The Doctor is In

Srini will have a regular presence on the blog with a new segment called "Ask the Doctor". He will answer questions presented from readers that may not be covered in the Frequently Asked Questions section of the blog. Should you wish to have a question answered by the doctor, please leave a comment or send our team an email (see "Who We Are" tab).

Welcome Dr. Srini! It's nice to have you as part of our team!

Stephen

Name That Car Contest

2010-07-21T10:23:00.001-05:00

A colleague sent me a few screen shots this morning of vehicles we captured during a collection. After looking at them, I went back and looked at information from another collection. I thought it would be fun to make a little contest out of the vehicles in our scans. Each of the cars below were captured during collections while they were either stopped at lights or parallel parked.

Rules of the contest: Send me an email with the number above the vehicle along with make and model. The first person that correctly identifies all seven vehicles wins a Baker travel mug, as pictured. I will verify vehicles using pictures captured during our collection and manufacturer websites. The contest closes on Wednesday, August 4th at 5 pm central. If nobody gets them all right, the person with the most, wins. Baker employees are not eligible to win, but submit guesses anyway. The contest is not open to individuals outside the United States - nothing against you, but it would require a trip to the post office. I will post the name of the winner and notify them via email. I have the right to cancel the contest at any point if you don't play nice!

Enjoy the contest, please leave comments and feedback. Entries to the blog are dictated by you, the reader.

Thanks,
Stephen

Updated Website

2010-07-01T07:00:00.002-05:00

It's with great pleasure that we present an updated website for our blog. The new site will continue to evolve and new postings will be written regularly.

Some of the new features include:

Frequently Asked Questions

More in-depth questions regarding Mobile LiDAR

Who We Are

A few of the Baker staff who eat, drink & dream Mobile LiDAR

Where We Have Been

A sampling of places we've performed projects and mention in postings

If you have questions not found in the FAQ's or a recommendation for a future post, please let us know.

New Mobile LiDAR Vehicle

2010-06-30T11:00:00.002-05:00

We have recently added a Honda Big Red (although green) to our Mobile LiDAR fleet. The customization occurred over the course of a weekend thanks largely to Wayne's Body Shop in Jackson, MS. In addition to fabricating the rack and mounts, the roll cage was shortened to allow for seamless loading & unloading into our dual-axle fiberglass trailer. The trailer has a 300 gallon fuel tank to allow us to access remote areas and deploy the UTV for rapid survey activities. The acquisition and deployment of our new tool shows Baker's continued commitment to Mobile LiDAR and it's applications - no matter where jobs may take us.

Again, our thanks goes out to Wayne's Body Shop for their rapid turn-around and superior work.

Yazoo City Tornado: Part 3 – Visualization

2010-05-25T12:39:00.001-05:00

Wrapping up our posts on the Yazoo City tornado, where we previously discussed mobilization in Part 1, damage surveys in Part 2, we are completing the trilogy with data visualization. Prior to, and following the field collections, the one question we kept getting asked was whether we’d get data that could be used for anything other than debris volume calculations, or photo interpretation; after all, no one has done this before, and if you’ve got a big pile of jumbled debris, will the resolution be fine enough to enable the processing staff to recognize what they are looking at? The results are a resounding YES!

The key is to create a seamless colorized point-cloud, which combines the LiDAR data (including laser return intensity) with the RGB values from the captured images (see Measuring Systems - Part 2); bringing the 2D images to life in a 3D environment.

Image of the Save-alot Grocery Store

Yazoo Motors Service Shop. Building 2 (left) lost the roof and most of the back wall. While building 3 (far right), a mere 80' away was completely leveled. Click here to see the original photograph of building 2.

Close-up view of collapsed wall in above image. The high-density of LiDAR points makes it easy to count each cinderblock, or identify the electrical service still attached to the façade.

Yazoo City Tornado: Part 2 – Damage Surveys

2010-05-21T06:09:00.014-05:00

Continuing our previous post on the Yazoo City tornado (See Part 1), it’s sometimes difficult to really wrap your brain around the phrase “catastrophic damage”, or “utter devastation”, and visualize what that really means. The use of Mobile LiDAR in damage surveys/assessments aids in the visualization component by not only capturing images (a picture is worth a thousand words), but also by creating a 1:1 model of the real-world. We can all pretty easily visualize a forest or a mobile home, but each of us would have a different interpretation from a news report that simply states “mobile homes and forest leveled by tornado”. Would you picture this?

Quantifying damage and putting a real measurable value to comprehend “debris”, needs more than just superfluous adjectives (or expletives if you’re so inclined). You need a concrete method to calculate volumetrics (how many dump truck loads is that?), assess damage, and provide usable data for disaster modeling.

The above image is of the Mississippi DOT Maintenance Facility (Bing Bird's Eye - Google StreetView). While, below is a picture of the Yazoo Motors Service Shop (Bing Bird's Eye).

Part 3 in the series will be forthcoming. It will address visualizations from the collected data.

This isn’t Kansas Toto

2010-05-18T08:54:00.000-05:00

Since we brought our system online last September, we haven’t had the opportunity, or need, to showcase our rapid-response capability. That changed with the devastating set of storms that rolled into the deep-south on April 24^th, which spawned an EF4 tornado that was on the ground for an astonishing 149 miles!

On the Move

Once the debris settled into place, we quickly re-routed the system to Yazoo City, MS, which at the time was en route to Florida for a project with the DOT. We picked Yazoo City because it was one the harder hit areas (the wedge funnel was over 1.75 miles wide in Yazoo City), and it presented the opportunity to perform widespread damage assessments.

Johnny on the spot

Five hours (and 280 miles) after re-routing the Mobile LiDAR system, we were on-site. We’ve always said that the key to the system is mobility, and the ability to rapidly deploy for emergency situations. When we rolled into town, we knew our response couldn’t have been any better when only the emergency management responders, local media, and storm-chasers were on the scene. The picture to the right shows the remnants of Hillcrest Baptist Church and the devastation a storm of this magnitude can cause.

For anyone that’s watched the Discovery Channel’s Storm Chaser’s television series, you’ll likely recognize Reed Timmons’ TVN “Dominator” tornado intercept vehicle in the below image. Although the Dominator is built to withstand high winds and hail…we think our system looks better.

This is the first in a series of blogs showing information collected in the aftermath of the late-April tornado that devastated Yazoo City, MS. Baker has had a long presence in Mississippi - our Jackson office is the second oldest in our firm at 60+ years. Our thoughts are with those you have been impacted by this storm.

The Size of Data - Zettabyte?

2010-05-04T12:45:00.004-05:00

I spent a few hours this past weekend helping my wife clean out our home office. In all the clutter, she found a case for 3.5" floppy disks containing about 50 disks. While we perused the labels on the disk - HP Printer Driver Disk 1 of 3, GIS Topics (senior elective), endless blanks - we searched the house for a computer with a disk drive capable of determining the need to keep any of them. Of the 3 computers in our home, we came up empty handed.

After chatting a bit about the need to keep things we didn't even know existed in the first place, my wife relented and I threw them in the garbage. Then I promptly removed them from the garbage. As my wife brought to my attention, the same person who's going to rummage through garbage to find personal information, probably has a drive that somebody else threw away. So, as I began destroying the disks, I contemplated the size of the data they contained. After all, it's interesting to see how technology, and storage, has developed over the past years or decades.

Over the past 20 years, we've witnessed the size of data and what we store grow to astronomical levels - levels that even require the invention of new words. From kilobytes, megabytes, gigabytes, terabytes, petabytes, exabytes to zettabytes - One zettabyte is equal to one million petabytes, or 1,000,000,000,000,000,000,000 individual bytes. (The yotabyte is next.)

To give you an idea of the amount of data we capture with the system, I've compiled a table presenting rates given the camera and laser frequencies:

Measurement Frequencies	50 kHz	100 kHz	200 kHz
Camera Rates
Cameras Off	3 MB per second	6 MB per second	12 MB per second
1 frame per second	13 MB per second	16 MB per second	22 MB per second
2 frames per second	23 MB per second	26 MB per second	32 MB per second
3 frames per second	33 MB per second	36 MB per second	42 MB per second

Looking at these numbers, it would take about 0.034 seconds to fill up one of those disks I threw away - when the system is working at peak performance. Our operators would need fast hands and a steady supply to keep up with the system. Thankfully, we have a constant supply of hard drives to transfer information from the vehicle to our processing facilities.

With the advancements in computer processors, memory, video drivers and software, we have come a long way with what we're able to effectively manage. The slide show prepared for Baker's 70th Anniversary provided me a glimpse of where we've been...

I can't imagine processing Mobile LiDAR data with that computer - although it cost significantly more than the systems we use today.

Happy 70th Baker! Here's to another 70!

It's Official: 3D is the New Standard

2010-04-07T16:44:00.003-05:00

Growing up, I felt I was more fortunate than my brother when it came to not having to wear glasses (especially those hideous Army BC glasses). Today when discussing glasses, I'm not talking in terms of optical power, but rather Anaglyph versus Polarized.

Movies and TV
Chances are you have likely seen a movie in 3D. With the proliferation of Avatar and movies from Pixar there is a growing awareness and desire for 3D. At 2, my son sat through Ice Age: Dawn of the Dinosaurs with his polarized glasses on the entire time. Even now, if you have $2,500+ you can purchase a 3D DLP or LED television (3DTV). There are announcements constantly about the progression of 3D channels to supply content to these devices.

The Internet
You may not have noticed a recent change to Google StreetView. To be honest, it took me by a little bit of a surprise. Below is a screen capture of the I-110 interchange I've discussed in this blog before. Notice the new icon. There have been many times where I have shown our Mobile LiDAR collection of this interchange in 3D using anaglyph glasses.

Mobile LiDAR
We have been presenting 3D animations and renderings of our Mobile LiDAR collections for quite some time. (Below is the same expanse of the I-110 interchange as shown in the new StreetView.) Looking at 2D images does not provide a measure of depth that is afforded with this information.

Revisiting the Mississippi River Levee collection, I've created an image that can be viewed in 3D using anaglyph glasses.

I now wear glasses - not because of a loss of vision, but to gain perspective.

If you would like a pair of anaglyph glasses to view the blog, send me your address and I'll mail you a pair.

Clouds - Not the Fluffy Kind

2010-03-11T15:59:00.001-06:00

Following up on the "Question of the Day" post, I wanted to share a video that was produced of the I-110 collection in Baton Rouge. The video was part of a presentation given earlier this week at the National States Geographic Information Council Mid-Year Conference in Annapolis, Maryland.

The collection consisted of 27 different approaches to the interchange and took about one and a half hours. The dense collection of points is commonly referred to as a Point Cloud - Wikipedia has a limited definition. The cloud shown in the video is composed of 491 million points.

Neither snow nor rain nor heat nor gloom of night...

2010-02-12T15:22:00.000-06:00

With the recent snow storms impacting the country, I thought of no better topic than a discussion of weather and Mobile LiDAR. It is relatively easy to work around localized weather events when utilizing a vehicle as opposed to an airplane or helicopter. But sometimes, it's absolutely necessary to work in such conditions.

As discussed in earlier posts, LiDAR is an active sensor which uses a laser to measure distance to an object (same premise as total stations - traditional surveying instrument). Therefore, our system can operate day or night and in virtually every weather condition. We have several examples of night collections (Downtown Norfolk and I-85/285 in Atlanta), rain conditions (The Narrows - State College, PA) and now snow as shown below.

The image above was captured at our Beaver, PA office during snow flurries. The image is colored by height to show all the snow in the scan (red dusting of points). While the image below illustrates the same collection with the snow "cleaned" from the scan. There are several different ways to accomplish this. But, it simply boils down to the intensity of the reflected light from the snow flakes and the elevation of those points. Rain and snow each pose various processing challenges, but when you need information, sometimes it takes a little extra effort.

Question of the Day

2010-01-26T21:01:00.000-06:00

Typically, when I make presentations on Mobile LiDAR, I take a brief moment to step into a point cloud to introduce the audience to the unlimited perspectives one can take when visualizing the information. Taking the 3D data and flattening it into a 2D screen capture does not do the information justice.

In today's presentation, I pulled up an interchange system with 4 levels of interstate highway and ramps with a similar aspect to what you see below - an aerial view. The question from an attendee was (to paraphrase) "how do you get an aerial view from a system mounted on a suburban?" My response was to make an analogy to ArcGIS and various feature datasets as these were well versed GIS users. I have had this question in the past but moved about the room to represent the change in perspective.

Having spatially sound, 3D information allows for an infinite number of perspectives - includes the position of the observer, target and a field of view. This ability provides the framework for a number of applications including line of sight analysis, obstructions, glide slopes, transportation/infrastructure design and 4D modeling.

Measuring Systems Part 2 - Lasers and Cameras

2009-12-29T15:29:00.000-06:00

Background

Continuing with our series on Baker's Mobile LiDAR system (See Part 1), we introduce you to the lasers and cameras. We will discuss the basic overview and specifications of the sensors. After all, the information captured with these four sensors is what you really want to see and utilize.

The images below depict an image captured with one of the onboard cameras and a colorized point cloud derived from the laser data and the picture (See our Bedford Springs post)

Lasers

Frequency & Returns
Our vehicle utilizes two Optech lasers - their LYNX Mobile Mapper™ system. The system allows us to collect at different rates (50kHz, 100 kHz or 200kHz) depending upon specific project requirements.

Building upon the technology developed for aerial systems and the need to penetrate tree canopies, the system is also capable of measuring multiple returns of the laser (up to 4). This ability allows for the capture of information behind hedges and through other brush. From the multiple returns, we're able to derive more complete "bare earth" elevation models.

Accuracy & Precision
Basically, precision is a measure of repeatability of a measurement. The lasers have a defined precision of 7 mm. Surveying total stations, by comparison, vary from 2 to 7mm depending on manufacturer, type and target (reflectorless total stations are generally less precise when used as such).

Often times, that term "accuracy" is thrown around indiscriminately, misinterpreted, misrepresented and, quite truthfully, over exaggerated. There are a number of ways to measure accuracy and a number of processes that either improve or reduce accuracy. In the most basic sense, we are realizing raw accuracies from the system itself of between 3 and 8 cm. Using ground control and point cloud constraint measures, we are realizing accuracies in the neighborhood of 1.5 - 4 cm. *There are a number of dependencies and each project is designed and performed to specifications to meet accuracy requirements.

Accuracy will be greatly expanded upon in a future blog. We will review what dilutes accuracy, what procedures we employ and how we establish ground control.

Safety
The light produced by the lasers is not visible and is eye safe at nadir. Therefore, drivers in surrounding vehicles and bystanders are safe from injury by the laser and distraction.

Cameras

We have two 5 mega-pixel cameras on our platform. They can measure up to 3 frames per second depending, again, on project specifications and requirements. We can position them forward or behind the lasers. They are also mounted in brackets that allow for a full range of orientation. If interested in a sign inventory, the passenger side camera may be positioned forward of the laser facing in the direction of travel while the driver side camera may be positioned behind the laser facing backward. For assessing pavement, the cameras would be located in the rear and pointing down.

From the images, we're able to develop a range of products from colorized point clouds to movies and attributes.

The rapid reconfiguration of the sensors (both laser and cameras) allows our operators to tailor a collection to a specific set of goals and products.

Mississippi River Levee

2009-12-17T13:37:00.000-06:00

Recently, we surveyed a few miles of the Mississippi River Levee south of Baton Rouge, LA using the Mobile LiDAR vehicle. At first, there were two things we wanted to learn from the collection. Our primary concern was the ability to capture the toe of slope of the levee with the system - the reasoning behind raising the sensor platform higher than the luggage rack. As you can see from the screen captures below, we didn't have any trouble with that test.

The second phase of testing dealt with camera settings. Since the sun angle changes rapidly with the vehicle in constant motion, our crew tested different collection techniques and settings in an attempt to have consistant brightness. Our goal is to limit the patchwork affect that is slightly visible in the roadway of the image above. With new software we've employed, we're able to then perform basic color matching to smooth out those regions.

Now that we have this information, we have elected to perform an assessment of "soft targets". We are performing field surveying in support this assessment - the results of which will be shared upon completion.

Measuring Systems Part 1 - Positioning

2009-11-23T17:54:00.001-06:00

Background
In traditional Surveying & Mapping, points are determined by measuring an angle and distance to an object from an instrument over a known point (X, Y, Z or elevation). We have all seen, at one point or another, a person at a total station locating a rod held by another field crew member - often while we zoom past at highway speeds.

Now, with Mobile LiDAR, we are Surveying & Mapping at highway speeds.

In order to better understand how accurate measurements are collected from our vehicle, it is important to know the instruments onboard and the function of each. As individual sensors, they do not provide an adequate solution. But, when used as part of a system, they provide the foundation for accurate information.

The purpose of this post is to provide a basic overview of our system. Additional parts will cover the lasers, cameras and other components and processes which provide a complete solution. If you have questions, please leave a comment.

Global Positioning System (GPS)
The primary method of location for the vehicle is GPS. We utilize 2 onboard units to provide the position of the vehicle as well as the heading (having a known baseline, distance and direction, between antennas provides a measure of direction of the vehicle). The fundamental issue with GPS as a sole (hence I used primary) source of positioning is that we measure a position one time per second. For those of you breaking out your calculator, that equates to 88 feet per second when traveling at 60 mph. In that second, our lasers could have measured 400,000 points (covered in part 2, stay tuned). Therefore, we rely on our second measurement instrument.

Inertial Measurement Unit (IMU)
The IMU measures the attitude (roll, pitch and yaw) of the vehicle, much like an aircraft, at a rate of 200 times per second. By measuring those changes in direction about the X, Y and Z axis, we are able to calculate the vehicle position at those increments. Using interpolation, we are able to further refine intermediate positions.

Distance Measurement Instrument (DMI)
The often overlooked member of the measurement family is the DMI. Barely noticeable and not mounted on the "LiDAR Wing", the DMI has two distinct purposes: determine the distance traveled by measuring the revolutions of the wheel 1,024 times per second and tell the system when the vehicle is stopped. Since there is drift in GPS and the IMU, the DMI basically determines when the wheel stops revolving. By measuring the diameter of the wheel and calculating circumference, we also know the distance traveled per partial revolution.

For NASCAR fans: since we measure the diameter of the wheel at rest, the circumference of the wheel is calibrated while we're driving and GPS provides a good solution.

For non-NASCAR fans: as we drive, the tire will begin to heat and will build pressure thereby increasing tire circumference and impact the distances measured by the DMI.

In a nutshell... one system helps calibrate another system. In a later post I'll cover what happens when we lose GPS!!!

Comments are moderated, so if you have a question, comment or suggestion please let me know.

Thanks for following!

Target of Opportunity

2009-11-23T15:30:00.000-06:00

Great Bridge Bridge

Virginia

Some time ago, we were in Chesapeake, Virginia performing a collection and demonstration. While driving, we saw a target of opportunity - the Great Bridge Bridge - and collected roughly 10 seconds of data. There was no purpose for the collection, but after processing I thought it would make an excellent example for showing point cloud samples - given the joint in the split drawbridge.

Above, I've render the point cloud two different ways. On the right hand side are point colorized by height/elevation only. There is nothing to differentiate one point from another as far as composition. On the left hand side I've included the intensity of the return in the colorization. From the intensity, you can begin to differentiate the striping, road and materials. Just as in traditional surveying where measured points will have an associated description, we can begin to see how intensity is used in point classification - more to come on that subject.

In addition, I've compiled a brief video of the bridge. Feel free to post comments and suggestions.

Subscribe to our Blog

2009-11-17T00:56:00.001-06:00

First, I would like to welcome you to the new and improved blog. I figured after spending the money to invest in a high tech piece of equipment, our blog should have the look and feel similar to our vehicle - not a default template.

I've been asked by several people how to go about following the blog without having to check the site daily. Therefore, here are two simple ways to get updated postings. Perhaps the easiest is to submit your email in the upper right-hand corner of the home page. You will need to follow a few steps to receive emailed blog posts.

Alternatively, you can consume the blog posts directly in Microsoft Outlook. First, right click RSS Feed in the Mail Items; then click "Add a New RSS Feed"; finally, type in http://feeds.feedburner.com/bakermobilelidar and click Add. The blog posts will appear similar to emails.

If you have any comments or recommendations for blog posts, please leave a comment.

2009 Texas GIS Forum

2009-11-05T17:02:00.001-06:00

The Presentations from the 2009 Texas GIS Forum are now available to download. Check out Mobile LiDAR: Surveys at the Speed of Business presented by Stephen Clancy. (Link to all other presentations)

Pipe Ladder Animation

2009-11-05T07:46:00.004-06:00

A few weeks ago, our Mobile LiDAR crew collected several roads around a heavy industrial area - including refineries and a railyard. Adjacent to and above our survey area was a complex labyrinth of pipes, fencing, railroad tracks and utilities. Making sense of all of the data could be quite daunting if looking at the entire collection. Utilizing animation, I've been able to illustrate how clipping the information can yield a new perspective. The video is a simple animation compiled showing a pipe ladder that we drove under. All of the information depicted was captured in seconds. The photograph shows the pipe ladder as taken with one of the onboard cameras.

Note: If you're not able to view YouTube videos and would like a copy, leave a comment with your contact information. Comments are moderated and your information will not be published to the board.

To Debunk or Not To Debunk - That is the Question

2009-10-28T13:18:00.000-05:00

I sit here writing this blog today facing a difficult decision to make. It's not a decision that I take lightly and one that I would gladly take advice on from you.

Shortly after installation of our system, we captured an area in Bedford County, Pennsylvania little known to the outside world - especially to those who no longer take the time to get off the interstate and enjoy such roadside attractions as the Corn Palace, Wall Drug Store or Weeki Wachee Springs. I am referring to Gravity Hill - a place described as:

"Cars roll uphill and water flows the wrong way. It's a place where gravity has gone haywire."

Since that day, I have avoided processing the collected data to keep from being the one to perhaps disprove what many have become to understand as a natural phenomena which occurs in an obscure, but beautiful, part of the Pennsylvania hills. Having grown up in Florida and traveled the state quite extensively, I am all too familiar with Spook Hill. I can vaguely remember sitting in the back of my grandparent's Cadillac when my grandfather put the car in neutral at the base of the hill and we proceed to roll backwards up the incline. To say that I was a little spooked was an understatement.

As a father, I look forward to these "less exciting" experiences and may allow the data to go unprocessed. Still, there is a part of me that wants to develop a bare-earth model and see that water really does flow up hill. I leave it to you, the readers, should this data be processed?

To find a "Gravity Hill" in your area, check out this list. Enjoy!

Baton Rouge - No Rest for the Crew

2009-10-09T09:33:00.030-05:00

Huey P. Long Bridge

Following our East Coast Road Show, the Mobile LiDAR vehicle arrived "home" to Baton Rouge. Although we managed to put over 3,000 miles on the vehicle in 3 weeks, our crew made their way back out into the field for collection of the Huey P. Long Bridge over the Mississippi River.

The bridge carries 4 lanes of US 190 (Airline Highway) and 1 line of the Kansas City Southern rail. Our Mobile LiDAR crew made two passes in each direction and various approaches to capture the underlying support structures, levee, railway and roadways.

LA DOTD Offices and I-110

After the collection of Huey P. Long Bridge, our crew collected the Louisiana Department of Transportation and Development office along I-110. They made several passes of the office building and surrounding approaches to generate dense coverage. After processing the trajectory, I created a Google Map of the drive. If you click on the location point, you can watch a YouTube video of the collection.

Atlanta - Spaghetti Interchange

2009-10-05T10:50:00.001-05:00

In order to minimize traffic in the collection, our crew worked through the early morning hours to capture almost 20 different approaches to the I85 - I285 interchange in Northeast Atlanta. Called the "Spaghetti Interchange" by locals, the data capture for the trajectory shown to the right took approximately 2.5 hours. The Smoothed Best Estimate of Trajectory (SBET) provides a constant position and orientation of the vehicle to process with the laser range data to calculate X, Y and Z coordinates of all measured points (point cloud) - the minimum type of processing performed.

The image above shows intensity merged with colorization by height (blues are lower than reds). The support structures, decking, retaining walls, barrier walls, and other roadway features were accurately captured with our vehicle traveling at 50 - 60 mph.

Pittsburgh Airport Data Collection

2009-09-18T00:45:00.001-05:00

Just days before the G20 Summit, Baker gained access to Pittsburgh Airport for an hour and a half. Using an escort vehicle, which maintained constant communication with Air Traffic Control, we surveyed two runways, several taxiways, approach lighting and the entire terminal. Our collection was highly successful. Due to the unobstructed sky, our GPS positioning yeilded constant accuracies of 8 - 12 mm for our trajectory utilizing a single base station.

To the left is an image showing intensity of runway 28L. There are two interesting components of this image. First, the bright dots to the left and right are field lights - their colored plastic lenses yeild higher intensity returns than their metal cases. Secondly, the rubber laid down by landing aircraft is clearly visible due, once again, to the intesity difference to the surrounding asphalt and white, reflective striping.

First Assignment - Bedford Springs

2009-09-16T23:20:00.001-05:00

Shortly after the installation and initial testing, we presented the vehicle to Baker's management at their Fall Manager's Meeting. Shown above is a colorized point cloud of data captured in under 20 minutes. Colorizing a point cloud assigns a red, green, blue value for each measured point from the pictures taken with the onboard cameras. The image shows a decimated point cloud - where only 50% of the points are rendered.

During collection, we also captured portions of US 220. The image above is not a black and white photograph. It is an image comprised of millions of points rendered by the intensity of the returned light from the laser. The red lines denote a cross-section and the graph shows the profile. Note the superelevation of the roadway as the highway curves to the right. Nothing special was done to derive these images.

Baker Mobile LiDAR - Day 1 System Install

2009-09-12T22:15:00.001-05:00

We decided on a Chevy Suburban 2500 (3/4 ton - 4x4) for our first Mobile LiDAR vehicle. A support structure was built to raise the sensors an additional 1.5' for better line of sight. We had custom drawers fabricated for our GPS and survey equipment. And the electrical system of the vehicle was upgraded to provide consistent, reliable power to the system.

The installation took place at our Beaver, PA office on September 12th. We had 4 Baker staff assist with the install: Aaron Morris - Program Manager, Stephen Clancy - Vehicle Manager, Justin Thornton - Vehicle Operator and Mark Anderson - Processing Technician. The team made quick work of the installation and stocking of the vehicle with supplies. Following the installation, we performed calibration drives and began testing.