Changes between Version 12 and Version 13 of Help/LeicaLidarDems


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Timestamp:
May 19, 2009 1:05:30 PM (10 years ago)
Author:
mark1
Comment:

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  • Help/LeicaLidarDems

    v12 v13  
    5252where the map names are as before, the imported point cloud rasters, and lidar_mosaic is the output name for the single concatenated raster set.
    5353
    54 [[Image(mosaic_with_holes.png)]]
     54[[Image(mosaic_with_holes.png,width=100)]]
     55Figure: Mosaic of point cloud data gridded at 2m resolution. Holes (no data) are shown as white.
    5556
    5657Assuming that there are only small holes in the data set and the DEM is required only within the lidar swath coverage, we can use the `r.surf.idw` command to interpolate over the lidar. This command will also interpolate into the GRASS region where the LIDAR is undefined.
     
    6061where the output raster, lidar_mosaic_idw, has been interpolated using an inverse distance weighted formula. As well as filling in holes within the lidar swath, this will also interpolate over empty parts of the GRASS region, resulting in possibly unrealistic data values.
    6162
    62 [[Image(interp_full_region.png)]]
     63[[Image(interp_full_region.png,width=100)]]
     64Figure: Interpolated point cloud data over full GRASS region.
    6365
    6466This can be improved if you wish by using a mask when interpolating the data. To create a mask, the easiest way is to use your input data at a low resolution. This creates a raster which covers the LIDAR swath but contains no holes in the data (assuming the resolution is selected low enough).  To import the data at a lower resolution , repeat steps 1-3 for each ASCII point cloud setting the `res` variable to a suitable value, e.g. 50.0 and outputting to a new map.  Then repeat steps 4 and 5 to create a raster covering the combined LIDAR swath.