Thursday, September 3, 2009

Psst! Hey! What's A LiDAR?

At the Super Modeler Conference last month in Boulder I heard the word LiDAR being tossed around a lot. Not wanting to appear stupid, I whispered to my seated neighbor "what is a LiDAR and where can I get one?" It sounded quite important. As it turns out, I was right. Jonathan Rumohr, one of the Super Modelers also known as WMU3D, offered this whispered response:

"Put simply, LiD
AR stands for Light Detection And Ranging. Basically, what happens when somebody wants imagery for their area, they can hire a LiDAR flight. It's just a small plane that goes out with a fancy camera that shoots light rays (laser beams) down at the ground and bounces them back up. No, we're not talking any Star Wars photon beams or anything. Everything is up ultraviolet to infrared range. Of course, these light rays measure the distance from the ground, back to the plane. This, accompanied with the GPS on the camera, allows for the creation of a virtual "cloud" of data points

"Once back on the ground, these clouds are looked at, and combined using software into what is called a DEM (Digital Elevation Map). From there, you can get several different kinds of DEMS. Since there is so much that the light rays can bounce off of, they are able to pick up things from tree heights, building heights, and sometimes even dense clouds. Therefore, it is possible to end up with three different DEMs for an area. One that is a tree-line elevation, one that is a building elevation map, and one that is strictly a terrain map. Those different anomolies are all taken out by software gurus way smarter than me! Just think of someone dumping a bunch of points or tiny lines in SU, and then trying to determine what they mean! Doesn't sound fun to me!

"Once your DEM's are created, that's where the SU fun begins! From those DEMS, we can make contours which we can then model, and submit to Google Earth. Unless the individual user has some pretty pricey equipment, the average SU user won't have access to a raw DEM, even though that would be the format that Google would like most. That's where the cities and municipalities come in. Most cities have a Geographic Information Systems (GIS) department these days. They would be able to submit that raw data for Google to use in large scale terrain maps!

I'm currently working with the University and the surrounding area on getting more of our recent DEMs to Google. Hopefully to them within the next month or so. It usually takes Google a bit longer to upload that data to GE, than the standard one week in the pipeline!"

hanks, Jon!

NOTE: In some cases apparently the LiDAR scan used in a municipality seems to be a low-resolution building elevations scan. In some cities this appears like gentle lumps scattered across areas that should be flat. Is that correct? Maybe a viewer knows.