[gdal-dev] Warp a file from two separate Lat and Long

Andrew Clegg ancl at pml.ac.uk
Thu Feb 18 12:37:14 EST 2010


Hi Luisa,

I've tried something similar in the past with satellite data. I had 3 
files, containing latitude, longitude and value stored as floats. I had 
some very minor success with the following solution (I got out an image 
but it seemed to drop to a very low resolution). I'm posting it more in 
the hope that someone else may be able to spot what I did wrong, because 
I would still really like to be able to do this.

My approach was to create a virtual dataset for each file:

sst.vrt (the values):

<VRTDataset rasterXSize="1296" rasterYSize="2030">
   <Metadata domain="GEOLOCATION">
      <MDI key="X_DATASET">lon.vrt</MDI>
      <MDI key="X_BAND">1</MDI>
      <MDI key="Y_DATASET">lat.vrt</MDI>
      <MDI key="Y_BAND">1</MDI>
      <MDI key="PIXEL_OFFSET">0</MDI>
      <MDI key="LINE_OFFSET">0</MDI>
      <MDI key="PIXEL_STEP">1</MDI>
      <MDI key="LINE_STEP">1</MDI>
   </Metadata>
    
   <VRTRasterBand dataType="Float32" band="1" subClass="VRTRawRasterBand">
     <SourceFilename relativetoVRT="1">sst.img</SourceFilename>
     <ImageOffset>0</ImageOffset>
     <PixelOffset>4</PixelOffset>
     <LineOffset>5184</LineOffset>
     <ByteOrder>LSB</ByteOrder>
   </VRTRasterBand>
</VRTDataset>

lon.vrt (longitude): (latitude is basically the same)

<VRTDataset rasterXSize="1296" rasterYSize="2030">
   <VRTRasterBand dataType="Float32" band="1" subClass="VRTRawRasterBand">
      <SourceFilename relativetoVRT="1">lon.img</SourceFilename>
      <ImageOffset>0</ImageOffset>
      <PixelOffset>4</PixelOffset>
      <LineOffset>5184</LineOffset>
      <ByteOrder>LSB</ByteOrder>
   </VRTRasterBand>
</VRTDataset>

I then tried to run gdalwarp on sst.vrt, trying either '-geoloc' or '-to 
METHOD=GEOLOC_ARRAY'.

Regards,

Andrew Clegg
Plymouth Marine Laboratory

Luisa Peña wrote:
> Greetings 
>
> I've used GDAL a few times but this is the first time that I'm lost on 
> what I can do with GDAL to solve my problem. I have 3 separate files, 
> one with my data, other with Lattitude and another with Longitude. 
> They have the same size and, as an example,  it means that Pixel (1,1) 
> of data is located in latitude retrieved from Pixel (1,1) from 
> latitude and longitude (pixel (1,1) from longitude). All of them are 
> in WGS84 but without GCP's points. 
> I need to create a georreferenced/rectified Geotiff with this data 
> and, to do that, I need lat and Long. How can I do this?
>
> Thanks
>
> Best regards,
> Luisa Peña
> S.Paulo, Brazil
> ------------------------------------------------------------------------
>
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev


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