[gdal-dev] R: Re: MODIS reprojection

[laura0]

If I try your command I get
ERROR 1: Unable to compute a transformation between pixel/line
and georeferenced coordinates for temp.tif.There is no affine transformation and no GCPs.


----Messaggio originale----

Da: ml-node+s1560n5047999h80 at n6.nabble.com

Data: 18/04/2013 16.18

A: "laura0"<lauramail at iol.it>

Ogg: Re: MODIS reprojection





	I use a similar command, without the -a_ullr argument
e.g.
gdal_translate -a_srs '+proj=sinu +R=6371007.181 +nadgrids=@null +wktext' <input HDF subdataset> <output tiff file>

On Thu, Apr 18, 2013 at 6:10 AM, Rutger <[hidden email]> wrote:

Hey Laura,



Since the MxD14.A2 products are already projected in the sinusoidal

projection there is no need to warp using GCP's. Fitting a polynomial

through some GCP's will always be less accurate then using the projection

the data is already in.



Somewhere in the metadata in the HDF there should be a boundingbox (corner

coordinates, in sinusoidal projection) for the specific tile you are using,

you can then assign these with the projection using gdal_translate. Once

assigned, you can use gdalwarp in the same way as you already described.



Youre gdal_translate command should look somewhat like this:

gdal_translate -of "VRT" -a_srs "+proj=sinu +lon_0=0 +x_0=0 +y_0=0

+a=<a href="tel:6371007.181" value="+556371007181">6371007.181 +b=<a href="tel:6371007.181" value="+556371007181">6371007.181 +units=m +no_defs" -a_ullr 2223901.039333

-3335851.559000 3335851.559000 -4447802.078667 <input HDF subdataset>

<output vrt file>



You can get the correct subdataset reference by running gdalinfo on you HDF.

The coordinates i used are for tile h20v12, so make sure you use the ones

from your tile. I used a vrt as output which you can use as an input for

gdal_translate, but its also fine to use Geotiff or anything else you

prefer.



Hope this helps.



Regards,

Rutger





















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