Heh heh, potting shed... like I do gardening
Yes I did build a laser scanner but instead of LIDAR which uses fast pulses and times them out and back, I used the older and easier geometric arrangement where it sends out a line and you use the camera to read in the line and convert back to 3D, then rotate the model a little and repeat.
To use that tho you do need to keep the camera and laser very still and aligned to a ridiculous degree or else it does go to pot. In that sense it could be the potting shed...
With LIDAR tho you do still need to hold the angle of the beam very predictable so unless your scanning very fast then I would ditch the LIDAR on a heli and go for a similar technique to the Saab 3D terrain thing I posted about on this forum. I.e. get a base with at least 3 or so digi-cams and take simultaneous photos of the terrain and then use the parallax to work out the 3D. You can fly a bit and take some more photos and using GPS re-align the photos digitally and see how much vertical displacement has occurred.
In principle thats not a supremely difficult challenge to take the photos and get them back into 3D. In fact there are some free software apps about to do that from a set of arbitrary positioned and directional photos to the same object. I was playing with Insight3D with MeshLab. Both free apps to play with. Doing it accurately and with enough points is hard and to classify the results and get something more meaningful than the point cloud is harder still.
Another option is David Laser Scanner which I think needs some alignment to do it right but is a possibility.
Since your in control of the scanning device (quad copter) then you can also send down ultrasonic pulses and time them and raster the flight path. But that would take ages to fly that circuit. There are some new 60GHz radar modules coming onto the market now for sensing the distance between cars in auto driving systems. Give this a few years and that would be a new possibility as well.
I have always had this idea that if you had a reasonably high res DEM model - say 10m then you could stand in some known position and direction and take photos and modify the terrain to be more accurate based on feature recognition. So you just walk (or fly) around and improve the terrain piecemeal by looking at the difference between what the photo says is there compared to what you have.
Anyway - lots of options. I wish I had more time to play around with this kind of thing.
http://www.viewing.ltd.uk/Scanning/index.htmhttp://www.outerra.com/forum/index.php?topic=391.0http://www.david-laserscanner.com/
