Wed, Mar 27 2002
18:10:38
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Request created by guest
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Subject: g.region Vask problem in lat/long
Platform: GNU/Linux/i386
grass obtained from: CVS
grass binary for platform: Compiled from Sources
Working in lat/long location, I found a small (unusual) error:
GRASS:~ > g.region -p
projection: 3 (Latitude-Longitude)
zone: 0
datum: WGS84
ellipsoid: WGS84
north: 17:46S
south: 26:54:30S
west: 19:59E
east: 29:22E
nsres: 0:00:30
ewres: 0:00:30
rows: 1097
cols: 1126
Now starting g.region, selecting menu 1:
V_ask error: Length out of bounds in call to V_const <- this warning
appears for 3 sec
IDENTIFY REGION
============================= DEFAULT REGION ========
| Default North:8:59:45S |
| |
| ======= YOUR REGION ======= |
| | NORTH EDGE:17:46S_____ | |
| | | |
Def. West |WEST EDGE | |EAST EDGE | Def. East
15:59:59.9919:59E_____| |29:22E_____|
| | SOUTH EDGE:26:54:30S__ | |
| ============================= |
| |
| Default South:29:00:15S |
=====================================================
PROJECTION: 3 (Latitude-Longitude) ZONE: 0
Default GRID RESOLUTION Region
0:00:30--- East-West --- 0:00:30___
0:00:30-- North-South -- 0:00:30___
The west value makes me unhappy. Looks like a rounding problem somewhere.
Markus
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Wed, Mar 27 2002
18:17:15
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Mail sent by guest
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Ah! Only now, after submitting, I found that the default region is
g.region -dp
projection: 3 (Latitude-Longitude)
zone: 0
datum: WGS84
ellipsoid: WGS84
north: 8:59:45S
south: 29:00:15S
west: 15:59:59.999982E
east: 34:00:29.999982E
nsres: 0:00:30
ewres: 0:00:30
rows: 2401
cols: 2161
I slighly change the report:
The field of default region in the g.region menu is too long and writing
into the current region. If there are no objections we should limit the
field length in
src/libes/gis/edit_cellhd.c
Markus
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Wed, Mar 27 2002
19:27:01
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Glynn Clements <glynn.clements@virgin.net>
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Date |
Wed, 27 Mar 2002 18:26:07 +0000
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To |
Request Tracker <grass-bugs@intevation.de>
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grass5@grass.itc.it
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Subject |
Re: [GRASS5] [bug #992] (grass) g.region Vask problem in lat/long
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<20020327171038.CEBFF139C9@lists.intevation.de>
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Request Tracker wrote:
> Subject: g.region Vask problem in lat/long
>
> Platform: GNU/Linux/i386
> grass obtained from: CVS
> grass binary for platform: Compiled from Sources
>
> Working in lat/long location, I found a small (unusual) error:
>
> GRASS:~ > g.region -p
Can you tell us the default region (rather than the current region),
as it seems to be the default West value that's causing the problem.
> Now starting g.region, selecting menu 1:
> V_ask error: Length out of bounds in call to V_const <- this warning
appears for 3 sec
> The west value makes me unhappy. Looks like a rounding problem somewhere.
Well, floating point can't represent exactly fractions where the
denominator isn't a power of two, so rounding errors will occur.
G_lon_format() (which generates the string in question) doesn't use
any specific precision, so you get the standard behaviour of "%f",
which is 6 digits after the point.
But how many digits should it use? Are whole seconds sufficiently
accurate? Unless you require accuracy better than thousandths of a
second, the argument should be converted to seconds and integer
arithmetic used.
--
Glynn Clements <glynn.clements@virgin.net>
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Sat, Apr 13 2002
10:32:55
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Status changed to resolved by gclements
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