Changes between Version 29 and Version 30 of Help/LeicaLidarDems


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Timestamp:
Feb 28, 2012 1:09:02 PM (8 years ago)
Author:
mark1
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  • Help/LeicaLidarDems

    v29 v30  
    6262=== Dealing with small holes ===
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    64 [[Image(mosaic_with_holes.png,width=150,align=right,margin=20)]]
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    6764If '''small''' holes are present in your data, say due to small lakes or removed noise, the easiest way to fill these in is to patch the data with a lower resolution version of the LiDAR. This can be done by changing the region to a lower resolution and resampling:
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    180 
    181 [[Image(interp_with_mask.png,width=100)]]
    182 {{{
    183 #!html
    184 <p style="text-align: center">Figure: Interpolated point cloud data after implementing a mask.</p>
    185 }}}
    186 
    187 To extend the coverage of your DEM, if required, it is suggested to patch on external DEM data. If you have access to a good quality DEM then use that, else the SRTM 3 arc second DEM is freely available and covers most of the globe between +-60 degrees latitude. To see how to make a DEM from SRTM data see the [wiki:Processing/SRTMDEMs SRTM DEM] page. Make sure to select the projection  the same as your LIDAR DEM. Also, be aware that the SRTM elevations are with respect to a geoid model and will need to be converted to the LIDAR vertical datum.
    188 
    189 Once you have an SRTM DEM of sufficient coverage you can patch the LIDAR and SRTM DEMs together, such that the LIDAR takes precedence. This means the lidar_dem should be the first of the input maps on the r.patch command. If the mask is still applied then remove it before patching:
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    191 10. '''`r.mask input=<maskmapname> -r`'''
    192 
    193 11. '''`r.patch in=lidar_dem,srtm_dem out=combined_dem`'''
    194 
    195 [[Image(combo_srtm_lidar.png,width=100)]]
    196 {{{
    197 #!html
    198 <p style="text-align: center">Figure: Interpolated point cloud data after implementing a mask with SRTM DEM data to fill in the rest of the region.</p>
    199 }}}
    200 
    201 To output the DEM (as ascii) and set null values as 0:
    202 
    203 12.    '''`r.out.ascii input=<DEMmapname> output=<outputDEMfile> null=0`'''
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