Defining Accuracies

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

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

*References to: There's a Map on My Lap! By: Tish Rabe; Dr. Suess Enterprises, LP Copyright 2002

Mobile LiDAR: Projects at a Glance

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

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

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