[gdal-dev] Rotate unreferenced tiff file by -90 degrees

[Zoltan Szecsei]

On 2011-03-17 15:34, Frank Warmerdam wrote:
> On 11-03-17 05:09 AM, Wesley Roberts wrote:
>> Dear gdal'ers
>>
>> I am working with TRMM rainfall data from an HDF5 file (converted 
>> from hdf4
>> to hdf5). I am able to use gdal_translate to extract the gridded data 
>> from
>> the HDF file using the following command.
>>
>> gdal_translate -of GTiff
>> "HDF5:"3A25.071201.6A.h5"://DATA_GRANULE/PlanetaryGrid2/e_surfRainMean2"
>> test.tif
>>
>> Gdal_translate works a treat and writes out the test.tif file perfectly,
>> however, the file is unreferenced and needs to be rotated by -90 
>> degrees. Is
>> it possible to do this using gdal_translate or do I need to make use of
>> gdalwarp as well? My tiff world file needs to look something like this
>>
>> 0.500000 0.0000000 0.0000000 -0.500000 -179.750000 36.750000
>>
>> Am I correct in assuming that a suitable proj4 statement might do the 
>> trick,
>> wrt assigning projection info and defining rotation? If so can 
>> someone point
>> me towards a document explaining the various proj4 declaration 
>> parameters,
>> or give me some advice on how to go about getting the data properly
>> referenced.
>
> Wesley,
>
> I think the easiest approach is to prepare a worldfile representing the
> current georeferencing in east-up or west-up orientation.  Then use
> gdalwarp to transform it to north up.
>
>   gdalwarp input.tif output.tif
>
> For "east up" I think the world file might look something like:
>
> 0.0
> 0.5
> 0.5
> 0.0
> top-left-x
> top-left-y
>
> You might need to fiddle around with the orientation a bit to get it
> right.
>
> Best regards,

But presumable the pixel sizes (1st & 4th) would not be zero?
-- 

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Zoltan Szecsei PrGISc [PGP0031]
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