[Gdal-dev] convert HDF ASTER to geotiff

[Jon Saints]

gdalwarp solved the problem. I used gdal form FWTOOLS
and it directly read and applied spatial reference to
my exported tifs.  

I thank the list for your help.
Jon


--- Andrey Kiselev <dron at ak4719.spb.edu> wrote:
> Jon,
> 
> On Mon, May 02, 2005 at 06:52:56AM -0700, Jon Saints
> wrote:
> > Yes, I agree that ASTER's come with ground control
> points, however,
> > when using gdal_translate it seems that the
> utility doesnt apply the
> > ground points correctly.
> 
> gdal_translate will not apply the control points,
> that is the task for
> special application called gdalwarp, gdal_translate
> just tries to
> transfer as much information as possible between two
> different file
> formats. gdalwarp will do the trasformation based on
> GCPs or
> corners coordinates.
> 
> Aslo I am sure you are missed important point: you
> need GDAL from CVS to
> get ASTER transformation working.
> 
> > My observation is this: In the raw aster image the
> corners (ul and lr)
> > of the raw image data are not the "corners" of the
> data. Along both
> > edges of the actual data there are no data values
> hold space as
> > padding. The actual image data is a slanted
> trazezoid padded on both
> > sides with no data values within the rectangle
> that is the raw aster
> > image. gdal_translate can apply the GCP points to
> the raw image, but
> > does so incorrectly. It applies the ul and lr
> values to the no data
> > padding of the raw image, rather than applying the
> point to the actual
> > corner where the actual data begins.  
> 
> There are two types of ASTERs. The first one is
> Level 1A. These scenes
> contains a set of GCPs and no corner coordinates and
> should be
> georeferenced by the some appropriate application
> (gdalwarp in our case)
> before using. You do not have other way of using
> these data.
> 
> The second type is Level 1B/Level 2 datasets. These
> ones contain both
> GCPs and corner coordinates (and rotation angle in
> addition); they are
> already transformed. These scenes can be
> georeferenced using both ways:
> GCPs and corners, results will be the same. I am
> prefer use the first
> approach, i.e., GCPs, but when I tried
> georeferencing with the corners
> result was the same. These two approaches are equal.
> And you can't
> apply the corner coordinates directly, the scene
> must be rotated
> (rotation angle provided in the metadata as well,
> but it is not actually
> needed).
> 
> Anyway, gdalwarp should solve all you problems with
> ASTER data.
> 
> Best regards,
> Andrey
> 
> PS.
> There is also the third type of ASTER scenes, the
> DEM (Level 3). It is
> georeferenced with GCPs, but sligtly differntly from
> the previous two
> types.
> 
> -- 
> Andrey V. Kiselev
> Home phone:  +7 812 5970603  ICQ# 26871517
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