Changes between Version 2 and Version 3 of Processing/demcompare


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Timestamp:
Sep 2, 2014 12:08:41 PM (5 years ago)
Author:
stgo
Comment:

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  • Processing/demcompare

    v2 v3  
    1111Unless you have an SSD available in your machine this will probably take a while.
    1212
    13 This will create a patched aster dem to compare to the lidar dem, this will not be smoothed and as such is the raw ASTER data. It will give 2 outputs on completion the first is only the area covered by the lidar files, the second is the area only covered by the lidar data. All outputs are in metres.
     13This will create a patched aster dem to compare to the lidar dem, this will not be smoothed and as such is the raw ASTER data. It will give 2 outputs on completion the first is only the area covered by the lidar files, the second is the entire dem. All outputs are in metres.
    1414
    15 Preferably the averages would be around 0 metres, but in practice it tends to be around 4 - 8 metres for UK data and varying for UTM data.
     15{{{
     16Temp folder created at:/tmp/grassdb-24688-115643
     17Calculation performed:GB13_10_2014_156_lidar_ASTER_bng.dem-ASTER_tiles.dem
     18The maps were compared in:WGS84LL
     19GB13_10_2014_156_lidar_ASTER_bng.dem was imported in:UKBNG
     20ASTER_tiles.dem sum     :1420384.824150
     21
     22GB13_10_2014_156_lidar_ASTER_bng.dem sum        :1444242.484528
     23
     24Comparison sum  :-23857.657357
     25
     26Difference statistics:
     27Min:            -69.939673828125
     28Max:            32.3908696899414
     29Sum:            -23857.6575275853
     30Mean:           -1.8243983732955
     31Median:         -0.985404
     32Absolute mean:  5.99935342521819
     33Std deviation:  8.54745020068044
     34Total cells:    39672
     35Non-null cells: 13077
     36
     37
     38Unmasked statistics:
     39Min:            -69.939673828125
     40Max:            32.3908696899414
     41Sum:            -24706.5998933041
     42Mean:           -0.641529909984007
     43Median:         5.49316e-07
     44Absolute mean:  2.21956360209108
     45Std deviation:  5.18281446074588
     46Total cells:    39672
     47Non-null cells: 38512
     48}}}
     49
     50Preferably the mean (non-absolute) for the lidar area would be around 0 metres, but in practice it tends to be around 2 to 4 metres for UK data and varying for UTM data.
    1651
    1752You can compare 2 dems already created using
     
    2358Which will skip the patching process and just give the dem outputs, if you use identical dems the outputs will be 0.
    2459
     60
     61=== Non standard outputs ===
    2562There are a few other options for deeper analysis of dems, and analysis of trends over years
     63
     64{{{
     65--output OUTPUT       output the resultant comparison DEM for inspection in
     66                        another program.
     67}}}
     68
     69Use this to inspect the created dem and comparison dem in envi, you can confirm figures from these.
     70
     71{{{
     72--histogram HISTOGRAM
     73                        Create a histogram and output it as a png at specified
     74                        location. Include file extension.
     75--png PNG               Create a PNG of the difference dem at the specified
     76                        location. Include file extension.
     77}}}
     78
     79The histogram option provides a better visualisation of the mean data. PNG can be used to provide quick looks at a heatmap of the data for comparison.
     80
     81
     82=== Batch processing ===
     83{{{
     84  --csv                 Output as csv format for batch processing.
     85  --script              Use with csv to indicate return rather than print
     86}}}
     87
     88Use these two for batch processing, can be useful for creating profiles of whole years worth of data. These would be helpful if we wanted to see our overall accuracy over the year.