Tuesday, April 24, 2012

Mobile LiDAR: Law #12

When the system encounters issues, take a breath and reboot

We have all been there; out in the boondocks with only a small section remaining to complete the days’ collections, then almost seemingly on cue, your equipment malfunctions.   Frustration sets in as you see your optimal collection window rapidly dissipating; and the last thing you want to do is waste half of the next morning to re-establish base-stations and calibrate the system, just so you can scan a miniscule segment of corridor, break down the base-stations, and backtrack to where you should’ve already been.

Murphy always seems to have a way to rear his ugly head, and Mobile LiDAR systems have a lot of individual, interconnected components that could fail.  Anyone that uses a computer has undoubtedly experienced unknown fatal errors that can halt productivity and drive you insane (just recently it wasn't the Mobile LiDAR system but a lovely Windows Blue Screen of Death that halted collection); now increase those complexities by a magnitude of six, and you start to get a sense of what a Mobile LiDAR operator can experience.  Unlike in the office environment, Mobile LiDAR failure points are not merely limited to the computer; there’s also the DMI, IMU, Control Rack, GPS (both on-board and base-stations), cameras, lever arms, a plethora of cables, and in the immortal words of Dr. Evil, “frickin’ laser-beams!”

If you’re lucky, an error report or warning will give you a good indication of where the problem occurred, and where you need to begin your examination, but that brings in the infamous “T” word – Troubleshooting.  A singular word that can instantly drive a cold shiver up the spine of any seasoned manager, and a resulting process that can single-handedly destroy your project schedule, or worse, the budget.  Sure, you could classify any activity to remedy an error or issue (especially the easy fixes) as a troubleshooting activities, but to me, “real” troubleshooting typically means “we have no idea what caused the problem, and we’re going to attempt various procedures, that likely won’t work, in a hope we narrow in on the problem”.

Inside the LYNX control rack.

In the heat of the moment, as you’re scrambling to find a solution, don’t let the frustration level build to the point where you blow a gasket and throw a tirade so animated your co-worker feels compelled to record it and post it online.  Nothing good can result from that video going viral and ending up on Tosh.0.  The old adage that sometimes you “lose sight of the forest for all of the trees” can certainly apply.  Step back, take a deep breath, clear your head, and look at it from a different perspective.  Electronics and field equipment can be very finicky sometimes; not to mention introduction of the occasional human error.  Regardless of whether the problem was initiated by a mechanical, or electrical, or a loose nut between the seat and the keyboard, sometimes all you need is that wondrous and magical cure-all…a reboot.


Thursday, April 19, 2012

Control Plan – Art or Necessity?

We like to think that the proper implementation of ground control, especially when you consider all factors (including cost), is more of an art than just a necessity.  Sure, anyone that has a basic understanding of the technology and general requirements could develop a control plan, but it’s likely to be either over-engineered (resulting in significantly higher cost), or insufficient to meet the true project requirements; higher costs and possibly additional field visits.  A quality control plan should create efficiencies across the board. 

Detailed Mission Planning efforts are a key component to the success of any field survey.  Mission Planning efforts for Mobile LiDAR surveys also include a concerted focus on required ground control.  Project requirements ultimately drive the implementation of control, but there are a myriad of factors and options that must also be closely considered. 

Control layout for a 4-lane divided highway.  Additional control is placed as the bridge to account for GPS outage.

The design and layout of a proper control plan needs to address: client requirements or standards, driving speeds, site access restrictions/limitations, sensor orientation, staff safety, localized obstructions (traffic, vegetation, elevated or sunken roadways, etc), style/type of target, terrain, control point spacing, and processing software limitations among others.  A control plan specialist is an integral part of the project team.  Their decisions and interpretation of local conditions could dictate the overall success or failure of the mission.  

The control layout for a city-wide Mobile LiDAR collection.  

A control plan specialist is an integral part of the project team.  Their decisions and interpretation of local conditions could dictate the overall success or failure of the mission.


Monday, April 16, 2012

Mobile LiDAR: Law #3

Hard Drives are Cheap – Time Isn’t

I can sum up Law #3 in two words – Be Efficient!  We make it a requirement for each individual on the team to perform their duties in the most efficient manner, and additionally strive to find better, faster, cheaper ways to perform that work.  But as manager’s we also have to look at initiatives holistically – and sometimes that means creating a little additional work for one group while counteracting that with greater efficiencies for another.

We see this most commonly in collection activities where, just as in real estate, “Location, Location, Location” surely comes to mind.  If there’s any confusion during collection activities about whether a small area should be captured or not, the standing order is undoubtedly to collect it.  An ounce of prevention is better than a pound of cure.  Yes, you are going to have a slightly higher expense for the field crew effort; and yes, data storage is absolutely a concern (especially with systems that are generating 48+ MB of data every second), but external hard drives are inexpensive.

Thankfully, as external storage drive capacity steadily grows, prices continue to fall.  You can run out to a local store and by 1TB of storage for under $100.  I remember back ten years ago when I upgraded my 16MB thumb drive for the new shiny 128MB version.  It was going to solve all of my data-transfer issues for $120.  Today, our LiDAR system would gobble up that device in 3 seconds.  But really it’s all relative.  The same approach to efficiency ten years ago is still perfectly valid today – only now we’re dealing with larger data volumes; and that volume presents other opportunities to enhance efficiencies.

Conventional surveys typically yield just a single-use dataset; but the high resolution and finite detail captured by a Mobile LiDAR survey presents numerous opportunities to re-purpose captured data (see “Re-purposing the Cloud”).  In this method, efficiency gains are not recognized immediately; but if you’ve got the time, and more importantly a projected user, it’s always less costly to leverage your current location and capture the data while you’re already there.


Aaron Morris is GIT Operations Manager in Baker's Ridgeland, MS office. In addition to his many daily responsibilities, Aaron also serves as the Program Manger for Mobile LiDAR operations, author and editor.

Friday, April 6, 2012

Point Classification

Baker's latest article for LiDAR News was published last week.  The article, Mobile LiDAR Point Classification, discusses the advantages to classifying features of similar type into groups. The grouping of features into classes provides the ability to isolate, remove or exploit smaller sets of information.  Due to the extensive detail and volume of data provided by Mobile LiDAR, point classification is incredibly useful for downstream applications.

The image above, presented in the article, shows classified features in an urban environment.  Street signs, vegetation, buildings, roads and other information are isolated into user defined classes.
Extents of tree canopies, outlines of building footprints, curbing and overhead wires are clearly depicted in the image above.  Ground points have been removed for clarity.
An elevation of a parking garage with DTM surface shows the undulating terrain.
If you have a recommendation for a future article, please leave a comment. 


Thank you to William for helping with content and images for this and past articles.  And, as always, thanks to Aaron for continued support, proofing and guidance.