[GRASSLIST:9901] Re: GeoTiffs shifted by 360 degrees after processing in GRASS

[Gross, Dorit (SDRN)]

Hi Markus,

Unfortunately the i.in.spotvgt script does not solve the problem. I can
import the Spot-Veg into Grass with the proper geometric reference. Instead,
the export back into GeoTiff (r.out.gdal) cannot handle the global
wrap-around and causes a 360 degree shift to the east. So might there be
another solution?

About i.in.spotvgt itself: I tried the import of the NDVI HDF without status
map and it seems to work nicely. Just a little note ... and maybe I have
overseen it ... it could be stated somewhere that also the log file is need
for the import.

Dorit

-----Original Message-----
From: owner-GRASSLIST at baylor.edu [mailto:owner-GRASSLIST at baylor.edu] On
Behalf Of Markus Neteler
Sent: 16 January 2006 16:53
To: Gross, Dorit (SDRN)
Cc: GRASSLIST at baylor.edu
Subject: [GRASSLIST:9858] Re: GeoTiffs shifted by 360 degrees after
processing in GRASS


On Mon, Jan 16, 2006 at 04:44:57PM +0100, Gross, Dorit (SDRN) wrote:
> Dear all,
> 
> I have a set of GeoTiffs that I import into GRASS to do some 
> processing and export them afterwards as GeoTiffs again. The problem 
> now is that GRASS exports the images shifted by 360 degrees to the 
> east.
> 
> 
> Corner Coordinates (before the import into GRASS):
> Upper Left  (-180.0044643,  75.0044643) (180d 0'16.07"W, 75d 
> 0'16.07"N) Lower Left  (-180.0044643, -56.0044643) (180d 0'16.07"W, 
> 56d 0'16.07"S) Upper Right ( 179.9955353,  75.0044643) 
> (179d59'43.93"E, 75d 0'16.07"N) Lower Right ( 179.9955353, -56.0044643)
(179d59'43.93"E, 56d 0'16.07"S)
> Center      (  -0.0044645,   9.5000000) (  0d 0'16.07"W,  9d30'0.00"N)
> 
> Corner Coordinates (after the export from GRASS):
> Upper Left  ( 179.9955357,  75.0044643) (179d59'43.93"E, 75d 
> 0'16.07"N) Lower Left  ( 179.9955357, -56.0044643) (179d59'43.93"E, 56d
0'16.07"S)
> Upper Right (     539.996,      75.004) (539d59'43.93"E, 75d 0'16.07"N)
> Lower Right (     539.996,     -56.004) (539d59'43.93"E, 56d 0'16.07"S)
> Center      (     359.996,       9.500) (359d59'43.93"E,  9d30'0.00"N)
> 
> 
> Has someone of you faced a similar problem? How do I receive a proper 
> georeference when exporting from GRASS?
> 
> The input GeoTiffs are a set of converted Spot-Veg HDF files using 
> GDAL.

Did you try to use the dedicated script i.in.spotvgt:

 http://grass.itc.it/grass61/manuals/html61_user/i.in.spotvgt.html

Maybe this solves the problem of the global wrap-around.
Please let us know.

Markus

> The -180.0044... degrees for the upper left X seems a bit odd, but 
> GDAL imports the Spot-Veg properly with these coordinates. I checked 
> the images in Erdas and they are correct. I also checked the corner 
> coordinates of the imported file insight GRASS and also here the 
> coordinates are correct. So apparently the shift occurs during the 
> export from GRASS into GeoTiff. At the moment I solve the problem by 
> reassigning the georeference to the GeoTiff after the export from 
> GRASS, but I would be more happy with properly exported images right 
> away.
> 
> Can someone help please?
> 
> Thank you,
> Dorit
> 

-- 
Markus Neteler     <neteler itc it>       http://mpa.itc.it
ITC-irst -  Centro per la Ricerca Scientifica e Tecnologica MPBA - Predictive
Models for Biol. & Environ. Data Analysis
Via Sommarive, 18        -       38050 Povo (Trento), Italy