Details Ticket 2986


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Serial Number 2986
Subject v.surf.rst wrong quant
Area grass6
Queue grass
Requestors hmitaso@unity.ncsu.edu
Owner none
Status open
Last User Contact Mon Jul 25 11:51:01 2005 (3 yr ago)
Current Priority 30
Final Priority 70
Due No date assigned
Last Action Wed Aug 31 20:47:52 2005 (3 yr ago)
Created Mon Feb 14 05:58:53 2005 (4 yr ago)

Transaction History Ticket 2986


Mon, Feb 14 2005 05:58:53    Request created by guest  
Subject: v.surf.rst  wrong quant

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

The quant result from query of elevation data computed by v.surf.rst (and s.surf.rst)
is not correct
testquant4 in cent, quant   (326)
testquant4 in cent, actual  (327.380127)
(should be 327)

The problem may be in
lib/rst/interp_float/output2d.c
 G_quantize_fp_map_range (params->elev, mapset,
                             (DCELL) zminac - 0.5, (DCELL) zmaxac + 0.5,
                           (CELL) (zminac - 0.5), (CELL) (zmaxac + 0.5));

This bug might have been there for years. Other parameters 
are quantized correctly.

Helena
Mon, Jul 25 2005 11:51:01    Mail sent by msieczka  
Helena,

Could you please explain how serious this bug is? I mean what problems it may
cause with v.surf.rst in Grass 6.1 for users.

Best
Maciek
Wed, Jul 27 2005 18:27:01    Mail sent by hmitaso@unity.ncsu.edu  
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Date Wed, 27 Jul 2005 12:26:55 -0400
From Helena Mitasova <hmitaso@unity.ncsu.edu>
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To Maciek Sieczka via RT <grass-bugs@intevation.de>
Subject Re: [bug #2986] (grass) v.surf.rst wrong quant
References <20050725095101.1B9AC1006CA@lists.intevation.de>
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Maciek Sieczka via RT wrote:
> Helena,
> 
> Could you please explain how serious this bug is? I mean what problems it may
> cause with v.surf.rst in Grass 6.1 for users.
> 
> Best
> Maciek
> 
> -------------------------------------------- Managed by Request Tracker

Not serious - nobody should be using the quant values for anything,
but the person who has reported this to me actually mistakenly tried to 
use those values and found the problem.
We (Markus, Helena) already tried tried to remove -0.5 and some other 
combinations for
calling the quant function, but that did not change anything.
So one has to digg into G_quantize_fp_map_range function, find out
what exactly is the function doing and what pair of DCELL zminac, CELL 
zminac would give the correct quantized minimum.
Unfortunatelly I have more pressing things to do right now than solving 
this, so it will have to wait until I have more time or somebody else 
can figure it out.
So please change its area to 6.0, 6.1 because it is still there
and keep it as low priority

thank you

Helena


Mon, Aug 1 2005 17:04:01    Area changed to grass6.1 by mneteler  
Wed, Aug 31 2005 20:47:52    Area changed to grass6 by mneteler  
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