Details Ticket 3961


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Serial Number 3961
Subject d.zoom: always alligns to resolution = data corruption
Area grass6
Queue grass
Requestors tutey@o2.pl
Owner none
Status open
Last User Contact Never contacted
Current Priority 30
Final Priority 70
Due No date assigned
Last Action Wed Jul 26 18:12:14 2006 (2 yr ago)
Created Wed Jan 4 23:04:57 2006 (3 yr ago)

Transaction History Ticket 3961


Wed, Jan 4 2006 23:04:57    Request created by guest  
Subject: d.zoom: always alligns to resolution = data corruption

Platform: GNU/Linux/i386
grass obtained from: CVS
grass binary for platform: Compiled from Sources
GRASS Version: 2005.11.16

When you d.zoom on a raster where data cells are not alligned to the resolution
(eg. usually ArcInfo rasters, SRTM tiles), your resulting region gets alligned
to the current resolution value instead of the cell borders. This causes serious
problems, examples:

1. r.to.vect output is shifted from cell's center
2. r.mapcalc 'copy=map' actually doesn't produce an exact copy, but it's shifted
version
3. reprojecting with r.proj will lead to wrong (shifted) results

This looks to me like a data corruption issue. I wonder how many people out there
are corrupting their data not knowing it.

For more info refer to http://grass.itc.it/pipermail/grassuser/2005-December/031624.html
and friends.

Maciek
Wed, Jul 26 2006 18:12:14    User changed to tutey@o2.pl by msieczka  
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