[gdal-dev] gdal_grid - cannot get interpolation to work

[Werner Reiche]

I'm trying to use gdal_grid to generate a .tiff file from a .csv file.
 
The problem I am encountering is that output file always contains 'no-data' values.
 
The command I am using is:
 
gdal_grid -txe -51.428009 -43.153992 -tye 46.112598 51.347198 -outsize 1024 796 \ 
          -a nearest:radius1=10.0:radius2=10.0:angle=0.0:nodata=0.0 \ 
          -l rs2_file_1 -l rs2_file_2 -l rs2_file_3 \ 
          -of GTiff -ot Byte rs2_file.vrt test.tiff 
 
I have also tried the following interpolation parameters:
 
# Results in all black 
# -a nearest:radius1=1.0:radius2=1.0:angle=0.0:nodata=0.0 \ 
# -a average:radius1=1.0:radius2=1.0:angle=0.0:min_points=1:nodata=0.0 \ 
# -a invdist:radius1=1.0:radius2=1.0:angle=0.0:max_points=1:min_points=1:nodata=0.0 \ 
 
# Results in all one shade of grey (average of entire image)
# -a invdist:radius1=0.0:radius2=0.0:angle=0.0:max_points=10:min_points=1:nodata=0.0 \ 

The .vrt and csv file used are shown below.
 
rs2_file.vrt 
:::::::::::::: 
<OGRVRTDataSource> 
<OGRVRTLayer name="rs2_file_1"> 
<SrcDataSource>rs2_file_1.csv</SrcDataSource> 
<GeometryType>wkbPoint25D</GeometryType> 
<GeometryField encoding="PointFromColumns" x="lon" y="lat" z="red"/> 
</OGRVRTLayer> 
<OGRVRTLayer name="rs2_file_2"> 
<SrcDataSource>rs2_file_2.csv</SrcDataSource> 
<GeometryType>wkbPoint25D</GeometryType> 
<GeometryField encoding="PointFromColumns" x="lon" y="lat" z="green"/> 
</OGRVRTLayer> 
<OGRVRTLayer name="rs2_file_3"> 
<SrcDataSource>rs2_file_3.csv</SrcDataSource> 
<GeometryType>wkbPoint25D</GeometryType> 
<GeometryField encoding="PointFromColumns" x="lon" y="lat" z="blue"/> 
</OGRVRTLayer> 
</OGRVRTDataSource> 
rs2_file.vrt (partial) 
:::::::::::::: 
lat,lon,red,green,blue 
-51.428009,50.522499,0,0,143 
-50.049011,50.720699,0,0,143 
-48.660004,50.902401,0,159,255 
-47.260010,51.067501,0,239,255 
-45.851013,51.215900,255,255,15 
-44.433014,51.347198,255,191,0 
-50.433014,50.657600,255,255,0 
-49.046997,50.844200,255,223,0 
-47.649994,51.014301,255,159,0 
-46.243988,51.167599,255,191,0 
-44.829010,51.303799,255,255,15 
-50.816010,50.593800,255,255,0 
-49.433014,50.784698,255,175,0 
-48.040009,50.959202,255,239,0 
-46.635986,51.117100,255,191,0 
-45.222992,51.257999,255,223,0 
-51.197998,50.528301,255,175,0 
-49.819000,50.724098,255,191,0 
-48.428009,50.903500,255,223,0 
-47.028015,51.066299,255,207,0 
-45.618011,51.211800,255,255,0 
-44.199005,51.340199,255,255,0 
-50.203003,50.661999,223,255,47 
-48.816010,50.845798,255,223,0 
-47.417999,51.013000,255,191,0 
-46.010986,51.163502,255,207,0 
-44.595001,51.297001,255,255,15 
-50.585999,50.598900,255,191,0 
-49.201996,50.787601,255,255,0 
 		 	   		  
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