[Gdal-dev] Re: GDAL with HDF on OSX

[Lorenzo Moretti]

>On Fri, Mar 26, 2004 at 01:35:12PM +0100, Lorenzo Moretti wrote:
>>  Grass does not import HDF directly from r.in.gdal but you have to
>>  convert to tif with GDAL. (Is it true Andrey ?)
>
>No. If you can convert HDF file using GDAL then you can import that file
>with r.in.gdal. Just use name of subdataset on input.

Andrey

I have enter in r.in.gdal box (GIS file input) subdataset file:

HDF4_SDS:ASTER_L1B:"/file_ASTER//AST_L1B_003_01102002101254_05222002150244.hdf":2

but I have this error in output:

ERROR: Input map is rotated - cannot import. You may use 'gdalwarp' to
        transform the map to North-up.

This error does not permit me to import HDF file into GRASS but I 
must use gdalwarp in terminal.
Is this correct?

>  > You must convert HDF files in GeoTiff for importing HDF in other
>>  programs like GRASS. Now it's impossible to import directly HDF.
>>  You must use gdalwarp utility.This is the method:
>>
>>  [lor:~] lor% /usr/local/grasslib/bin/gdalwarp -t_srs
>>  'projection_of_output' name_of_subdataset_of_hdf name_of_output_file
>
>It is not converting, it is warping. You will get completely different
>image on output, because input scene will be rotated. If you want
>just convert HDF subdataset into GeoTIFF you should use gdal_translate.

Ok it is warping but this method creates a geotiff file: I don't use 
gdal_translate.
I enter in terminal:

[lor:~] lor% /usr/local/grasslib/bin/gdalwarp -t_srs '+proj=utm 
+zone=33 +datum=WGS84' 
HDF4_SDS:ASTER_L1B:"/file_ASTER/AST_L1B_003_01102002101254_05222002150244.hdf":2 
/aster_tif/aster1.tif

I write at the end aster1.tif and I have a geotif output.

Is this wrong ?

>  > One geotiff file for any subdatasets: in Aster level_1B I have 15 Geotiff
>>  files
>
>Yes, that's true. Note, that subdatasets from the same instrument can be
>combined in the single multiband file (using simple Python script).

OK. I have 15 geotiff

>Some new HDF files have new szip compression
>Please, tell me what data uses szip? Never seen that before. Usually
>data distributers don't use any compression at all.
>
>						Andrey

I read this information in one small note in a web page (I don't 
remember in what site) for this format but like you I have not seen 
until now this method. HDF from distributor is without compression 
but I suspect that new HDF format will be much greater in size and 
perhaps this szip compression is for the future. I don't know it: 
it's only my opinion.

Bye

-- 
________________________________________________________________________
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