Hi!
I'm not sure but probably my question is related to the one below.
I'm trying to mosaic one MODIS images onto another with GDAL:
gdal_translate
HDF4_EOS:EOS_SWATH:"/Data/sat/GDAL_test/MYD021KM.A2011228.0925.005.2011229003113.hdf":MODIS_SWATH_Type_L1B:EV_1KM_RefSB
-b 1 /data/modis1.tif
gdal_translate
HDF4_EOS:EOS_SWATH:"/Data/sat/GDAL_test/MOD021KM.A2011229.1125.005.2011229195243.hdf":MODIS_SWATH_Type_L1B:EV_1KM_RefSB
-b 1 /data/modis2.tif
gdalwarp modis1.tif modis2.tif
Bu the results looks weird - the first image is on top of the second one
but it is very small, distorted and in the top-left corner (though they
cover approximately the same area).
Do I understand right that such operation would work only when the
target image georeference is defined by GeoTransform and not by GCPs?
Can I also ask if it is a big work to include ability of GDAL to warp
onto grid with GCPs (or RPC or geolocation array) ? And if it is planned
in some future?
Thank you!
Anton
On 12/15/2011 03:47 PM, Knut-Frode Dagestad wrote:
Hi,
Hróbjartur Þorsteinsson explained to me a near-hidden feature of GDAL,
namely to reproject one image onto the coverage of another.
Given two images:
imageA.tiff
imageB.tiff
Then an empty image can be created from image A with e.g.
$ gdal_translate -ot Float32 -scale 0 0 999 999 -a_nodata 999
imageA.tiff domainA.tiff
And then imageB can be warped onto the extent of this image simply with:
$ gdalwarp imageB.tiff domainA.tiff
domainA.tiff will then contain the data from imageB, exactly co-located
with imageA.
The problem is that this only works when imageA contains a geotransform,
and not when it contains only GCPs.
So my question is:
Is there any workaround to warp data from one image onto another image
which is geolocated by GCPs only?
With the -to option of gdalwarp it is possible to pass some parameters
to GDALCreateGenImgProjTransformer2(). In the documentation of this
function I find the following option:
"METHOD: may have a value which is one of GEOTRANSFORM, GCP_POLYNOMIAL,
GCP_TPS, GEOLOC_ARRAY, RPC to force only one geolocation method to be
considered on the source dataset."
http://www.gdal.org/gdal__alg_8h.html#94cd172f78dbc41d6f407d662914f2e3
But there is no corresponding option to force use of GCP_POLYNOMIAL for
the *destination* dataset. I guess this is a bad sign?
Thank you for any help!
Knut-Frode
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