LIDAR in Canyon

[LS_8750]

I'm working with some geologists on a landslide in a fairly steep canyon. They want to contract out some LIDAR work and have me fill in details on the ground and tie into some boundary.

I don't have any experience working with LIDAR, and I don't know how I'm going to get GPS control up in that canyon without some good old fashioned traverse.

We're talking about scope of work next week and I thought I might try to get some feedback here ahead of time so I can ensure everybody gets a good final product.

A couple things come to mind:

1. How do I merge the LIDAR data with my control?
2. How do I work with the LIDAR model to provide a good deliverable to the geologists and ultimately the client?

Does anybody have any experience working with LIDAR in circumstances such as this?

Thanks in advance and Cheers!

[Ian Wilson]

First, LiDAR is nothing more than a method of collecting remote data that is identical, functionally, to photogrammetry. The difference is, of course, that there isn’t any film used in LiDAR.

You will need to establish ground control for a LiDAR project, just as you would for a photogrammetry project. The product that will be delivered to you will be line compiled line work just as you would get for a photogrammetry project. The control is the tie in between your work on the ground and the LiDAR, just as it would be for a photogrammetry project.

You will get surface files as well as compiled planimetrics. The difference is that you may get a “cloud” view of the project surface, but you will probably not get any aerial photograph of the site.

In short, as far as you’re concerned, there isn’t any difference between LiDAR data acquisition and photogrammetric data acquisition.

The main difference lies in resolution.

This is a bit simplistic for a complete answer, but it’s Sunday and I need a day…

[RasterMaster]

Lidar is an active sensor unlike photogrammerty, passive. The technologies for the CCD "Digital" has become to a point where film is really no longer needed as it once was,in the air.

I am assuming this is a LiDAR flight. The ground will be controled via gps and the aircraft will carry gps corrodinates aswell. So to marry the two togeather is not a real big deal, provided you have the software.

The typical products would be a terrain modle, a DTM, trees/vegitation, Hillshade, slope asspect, or vectorize it, or just a big fat point cloud. The products you create are up to you depending on the type of software use. The possibillities are all most end less. Excellent technologie for large projects.

There are many software folks out there creating new and better programs. I like Virtual Geomatics because it has almost all of the tools needed for a mobile, static and arial LiDAR, of course Cyclone is a grate chioce for static.

RM

[coast]

Contact Marcus Glass at Aerometrics at (503) 312-5822. Please let him know I suggested that you call.

They have a helicopter based Lidar that gets the unit alot closer to the action. You would need to set and position several points in the project area and then gather GPS data on their flight day.

[RasterMaster]

The data I have used from Helicopter is rather choppy and really did not suceed, however that was done a few years back and maybe there is a way to mitagate that factor out for a better accuracy. If resolution is what you are trying to complete, then spec out the highest frequency scanner you can get.

[Ian Wilson]

The active/passive nature of the data collection really isn't that significant to the surveyor. It's rather like differentiating distances collected with a steel tape or an EDM "back in the day".

For the dozen GPS-Controlled Photogrammetry, LiDAR projects I've done, the observation files were turned over to the photogrammetry company for processing.

The critical items to discuss are the observation rate of the ground stations, usually 1 second intervals, and the overlap in time as far as when the observations need to begin and when to end. Often, the final coordination ws from the pilot who simply made a cell phone call to confirm that they were up and running and ready to take off and then again when they had landed and checked back in at their end.