Changes between Version 2 and Version 3 of Processing/LIDARDEMs

Timestamp:

Apr 9, 2008, 11:00:17 AM (17 years ago)

Author:

benj

Comment:

--

Processing/LIDARDEMs

@@ -45 +45 @@
 In the given example, there are a very few values between 20-30m at the bottom end, and a big gap at the top end before a small number of values above 590m (nothing between 240m and 590m). So it would be sensible to pick 30m as a minimum cutoff and 250m as a maximum. Note that because the histogram is on a log scale the difference in numbers of points at both ends is much larger than it looks at first glance.
 
-3. Open GRASS, select (or create) an appropriate UTM/WGS84 location and set the region appropriately for the dataset - easiest way is to look at the start of the trimmed lidar data file for the starting co-ordinates of the first line, set an approximate region from there, view the map in GRASS and then adjust the region appropriately.
+3. Check the LIDAR data projection in the header file. Open GRASS, select (or create) an a location in the appropriate projection and set the region appropriately for the dataset - easiest way is to look at the start of the trimmed lidar data file for the starting co-ordinates of the first line, set an approximate region from there, view the map in GRASS and then adjust the region appropriately.
 
 4. Read in the trimmed lidar file using r.in.xyz:
@@ -57 +57 @@
 }}}
 
-6. Generate an ASCII DEM as per [wiki:Processing/NextMapDEMs Creation of DEMs from NextMap data]:
+6. Reproject the dataset if necessary to match the projection of the flight data (should be the same, but conceivably won't be). See [wiki:Processing/SRTMDEMs Creation of DEMs from SRTM 90m data] for how to do this.
+
+7. Generate an ASCII DEM as per [wiki:Processing/NextMapDEMs Creation of DEMs from NextMap data]:
 {{{
 r.out.ascii input=<lidar_interp_map> output=lidar.dem null=0