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I have many CSV file in the form of lon, lat, Z that in would like to import into gdal for further processing. I need to do this on the fly in a python script so any step involving gdal_grid or anything else from the command line is not an option.

It seemed that creating a vrt xml would solve the problem but I am unable to get gdal to load the data.

Loading data this way seems to be such a common task I can't believe there is not a way to do this.

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  • I was already able to successfully create a CSV file with the corresponding vrt file that checked out with ogrinfo. However, I was unable to load it with a gdal python script.
    – denson
    Commented Jun 13, 2014 at 18:39

2 Answers 2

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Step 1: Create CSV file "xyztest.csv"

x,y,z
1,2,3
4,5,6
7,8,9

Step 2: Write a VRT file "xyz.vrt" that maps the previous file

<OGRVRTDataSource>

    <OGRVRTLayer name="xyztest">
        <SrcDataSource>xyztest.csv</SrcDataSource> 
    <SrcLayer>xyztest</SrcLayer> 
    <GeometryType>wkbPoint</GeometryType> 
        <LayerSRS>WGS84</LayerSRS>
    <GeometryField encoding="PointFromColumns" x="x" y="y" z="z"/> 
    </OGRVRTLayer>

</OGRVRTDataSource>

Step 3: Test with ogrinfo

C:\temp>ogrinfo xyz.vrt -al
INFO: Open of `xyz.vrt'
      using driver `VRT' successful.

Layer name: xyztest
Geometry: Point
Feature Count: 3
Extent: (1.000000, 2.000000) - (7.000000, 8.000000)
Layer SRS WKT:
GEOGCS["WGS 84",
    DATUM["WGS_1984",
        SPHEROID["WGS 84",6378137,298.257223563,
            AUTHORITY["EPSG","7030"]],
        TOWGS84[0,0,0,0,0,0,0],
        AUTHORITY["EPSG","6326"]],
    PRIMEM["Greenwich",0,
        AUTHORITY["EPSG","8901"]],
    UNIT["degree",0.0174532925199433,
        AUTHORITY["EPSG","9108"]],
    AUTHORITY["EPSG","4326"]]
x: String (0.0)
y: String (0.0)
z: String (0.0)
OGRFeature(xyztest):1
  x (String) = 1
  y (String) = 2
  z (String) = 3
  POINT (1 2 3)

OGRFeature(xyztest):2
  x (String) = 4
  y (String) = 5
  z (String) = 6
  POINT (4 5 6)

OGRFeature(xyztest):3
  x (String) = 7
  y (String) = 8
  z (String) = 9
  POINT (7 8 9)

All done. It may still be necessary to explicitly define that the input vrt is 3D. For example ogr2ogr conversion into shapefile creates a "POINT" type shapefile unless "-SHPT POINTZ" is used as a parameter.

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  • Question: How do you actually write the VRT file? In my case, I'm trying to convert a csv of points into a vrt to be used for gdal_grid, all inside a python script. I've looked seemingly everywhere, but all tutorials say is "here is a csv, and here's the resulting vrt," but don't actually say how to get the resulting vrt. Perhaps you can help? Thx
    – user20408
    Commented Dec 11, 2014 at 16:42
  • By hand, if you mean that. I believe I first just read and followed the example at gdal.org/drv_csv.html and once it worked I started to make my own modifications.
    – user30184
    Commented Dec 11, 2014 at 16:58
  • Well, not by hand. It looks like downloading the FW tool kit or whatever is how you obtain the VRT from CSV. Only thing is, I need to automate the conversion to VRT for a large amount of csvs, so doing it by hand is not viable. I tried os.system("ogr2ogr -f 'VRT' %s %s -nlt 'POINT'" %(tempvrt, rbcsv)) but get the error: "VRT driver does not support data source creation." Perhaps it's not possible to do in a script.
    – user20408
    Commented Dec 11, 2014 at 17:03
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If you have at least GDAL 1.11, you can open CSV files with the XYZ driver. The file must conform to the rules described, such as increasing X values, or the names used for the columns. In lieu of what your file looks like, here's a working example:

$ cat > my.csv
lon, lat, Z
0,0,3
1,0,6
0,1,9
1,1,2

$ gdalinfo my.csv
Driver: XYZ/ASCII Gridded XYZ
Files: my.csv
Size is 2, 2
Coordinate System is `'
Origin = (-0.500000000000000,-0.500000000000000)
Pixel Size = (1.000000000000000,1.000000000000000)
Corner Coordinates:
Upper Left  (  -0.5000000,  -0.5000000)
Lower Left  (  -0.5000000,   1.5000000)
Upper Right (   1.5000000,  -0.5000000)
Lower Right (   1.5000000,   1.5000000)
Center      (   0.5000000,   0.5000000)
Band 1 Block=2x1 Type=Byte, ColorInterp=Undefined
  Min=2.000 Max=9.000
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