[GRASS-user] LiDAR Data?

[Markus Metz]

Markus Neteler wrote:
> Rich Shepard wrote:
>
>>  There are two topographic quadrangle files that cover the project drainage
>> basin, and the data DVDs cost $200 each. I want to make high resolution DEMs
>> of the project basin and try to determine flood elevations for different
>> storm events from those. According to the data source, "All data are format
>> specific to ESRI GIS format. Data must be viewed using specialty software
>> capable of viewing .shp, geotif, and ESRI grid formats."
>
That sounds like these are no raw LiDAR data but already processed
data. Raster grids, in this case the GeoTIFF and ESRI grid data, are
usually end products after processing LiDAR data, and it would be
interesting to know what was done there in order to judge if these
raster grids are suitable for the planned analysis. The shapefiles
might hold LiDAR point clouds that can be processed with the LiDAR
tools:
1. v.outlier
2. v.lidar.edgedetection
3. v.lidar.growing
4. v.lidar.correction

optionally now
v.surf.rst or v.surf.bspline to generate a raster DEM

More in the already mentioned wiki page and the v.lidar.* manuals.

LiDAR point clouds should be imported as a vector and not a raster if
they are supposed to be processed with the v.lidar.* tools. LiDAR
point clouds come in different ways depending on the preprocessing
done. Sometimes there are no multiple return rates, sometimes
information about multiple return rates is stored for each point
(emitted pulse) in an attribute table, sometimes each return rate
represents one point, sometimes multiple return rates are in different
vector layers e.g. shapefiles. The v.lidar tools want each return rate
as a separate point, i.e. some preprocessing might be required if you
want to use the v.lidar.* tools.

>> I've not worked with
>> geotif or ESRI grid formats so any experiences of you folks with these
>> formats and LiDAR data will be much appreciated.
>
> For GeoTIFF, use r.in.gdal.
>
GDAL supports so many raster formats (>100 in 1.7.2) that chances are
pretty good that a given raster map can be imported by r.in.gdal.

Markus M