Tue, May 9 2006
14:20:55
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Request created by guest
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Subject: export of AAIGrid and arc incorrect
Platform: GNU/Linux/x86
grass binary for platform: Compiled from Sources
GRASS Version: cvs 08.05.2006
Hello,
concerning the export of AAIGrid (r.out.gdal) and ArcInfo Ascii Grid
(r.out.arc) an incorrect output occurs if the nsres/ewres in GRASS is not
equal - AAIGrid/arc stores only one value for res.
The difference between the resolutions is (in my case) small (3-> decimal
place) hence the incorrect export is only visible if high numbers of row/col
exist (high resolution imagery/covering continental scales).
The remedy is to resample the image to an equal nsres ewres. The problem is
located in the data format and not GRASS so I would suggest to either
1. prompt a warning if nsres != ewres
or
2. do an automatic resampling with equal nsres/ewres with an info prompt
otherwise the exported files have a wrong geolocation.
regards, Martin
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Tue, May 9 2006
16:40:05
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Taken by fwarmerdam
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Tue, May 9 2006
16:41:10
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Comments added by fwarmerdam
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I will ensure that the AAIGRID driver issues a warning message if the
geotransform cannot be properly represented (non-square pixels). I think
resampling on the fly would not be in the spirit of an exporter.
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Tue, May 9 2006
16:44:46
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Comments added by guest
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It seems that for GDAL 1.3.2 support was added to the AAIGRID
driver to use DX and DY keywords instead of CELLSIZE if these don't
agree. This is a "Golden Surfer" convention and may make the file
unreadable for ArcGrid, I'm not exactly sure. But there is no clear
need for a warning any more.
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Sun, Jun 11 2006
14:10:29
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Mail sent by msieczka
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What is the status? The most recent information is too unclear for me, sorry.
Maciek
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Sat, Nov 25 2006
11:18:44
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Mail sent by mneteler
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Martin,
can you please try again with r.out.gdal2? r.out.gdal was rewritten in GRASS
6.3 as C implementation (currently named r.out.gdal2).
Markus |
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Wed, Nov 29 2006
13:40:33
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Mail sent by wegmann@biozentrum.uni-wuerzburg.de
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To |
grass-bugs@intevation.de
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Subject |
Re: [bug #4438] (grass) export of AAIGrid and arc incorrect
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Date |
Wed, 29 Nov 2006 13:40:01 +0100
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Hello,=20
I am not totally sure if it works correct - import and export of the same=20
image works fine but doing resampling inbetween produces a shift in the=20
exported file.
I'll try to locate the error (gdal or elsewhere) and post to grass-bugs.
Martin
On Saturday 25 November 2006 11:18, Markus Neteler via RT wrote:
> Martin,
>
> can you please try again with r.out.gdal2? r.out.gdal was rewritten in
> GRASS 6.3 as C implementation (currently named r.out.gdal2).
>
> Markus
>
> -------------------------------------------- Managed by Request Tracker
=2D-=20
Martin Wegmann
DLR - German Aerospace Center
German Remote Sensing Data Center
@
Dept.of Geography
Remote Sensing and Biodiversity Unit
&&
Dept. of Animal Ecology and Tropical Biology
University of Wuerzburg
Am Hubland
97074 W=FCrzburg
phone: +49-(0)931 - 888 4797
mobile: +49-(0)175 2091725
fax: +49-(0)931 - 888 4961
http://www.biota-africa.org
http://www.biogis.de
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Sat, May 12 2007
17:54:58
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Status changed to resolved by mneteler
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Sat, May 12 2007
17:54:58
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Mail sent by mneteler
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Martin,
now r.out.gdal is a real C implementation in GRASS 6.3. Can you please try and
let us know if the problem persists? On the other hand, it would be a GDAL
problem then (to be reported there). I take liberty to close the report.
Markus |
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