<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-2">
<META NAME="Generator" CONTENT="MS Exchange Server version 6.5.7233.28">
<TITLE>ODP: [GRASS-user] MOLA data elevation problem</TITLE>
</HEAD>
<BODY>
<!-- Converted from text/plain format -->
<P><FONT SIZE=2>Dear Laurent<BR>
<BR>
There is in r.in.bin a -s flag(high bit means negative value) but when i used it, effect was the same.<BR>
The r.mapcalc fixed it. Now everything is ok.<BR>
Thanks for your advice<BR>
best regards<BR>
maciej<BR>
<BR>
Maciej Tomaszczyk<BR>
Polish Geological Institute<BR>
Geological Mapping Department<BR>
<BR>
<BR>
<BR>
-----Wiadomość oryginalna-----<BR>
Od: laurent.caribou@free.fr [<A HREF="mailto:laurent.caribou@free.fr">mailto:laurent.caribou@free.fr</A>]<BR>
Wysłano: Wt 2007-02-06 14:49<BR>
Do: Maciej Tomaszczyk<BR>
DW: grassuser@grass.itc.it<BR>
Temat: Re: [GRASS-user] MOLA data elevation problem<BR>
<BR>
Hello Maciej,<BR>
<BR>
It seems that your file contains negative values. They are coded with the values<BR>
form 32768 to 65535 with 32765 meaning -32768 and 65535 meaning -1 (you can see<BR>
in your histogram that you have values in the low value (0...) which are the<BR>
positive values and in the high values (...65535) which are the negative values<BR>
(-1...).<BR>
<BR>
I don't have Grass right here but you can check wether or not r.in.bin have a<BR>
flag to tell him to use to convert negative value.<BR>
<BR>
The other way would be tu use r.mapcalc with an expression doing the following:<BR>
if value<32767 return value ( the positive value kept as is )<BR>
else return value-65636 (convert to negative value)<BR>
<BR>
It should be something like (once again, I'm not sure of the syntax and I don't<BR>
have access to grass to check):<BR>
out=if(value<32767,value,value-65636)<BR>
<BR>
Let me know if it works an,d which solutions use used.<BR>
<BR>
Laurent<BR>
<BR>
<BR>
Selon Maciej Tomaszczyk <mtom@pgi.gov.pl>:<BR>
<BR>
> Hello Grass Users<BR>
><BR>
> I have problem with MOLA data, i managed to import MOLA binary file to grass<BR>
> using r.in.bin<BR>
> but some cells seems to have invalid values (see pictures in attachment).<BR>
> Anyone know how to solve this problem??? and set correct elevation values.<BR>
> Thanks in advance<BR>
> best regards<BR>
> maciej<BR>
><BR>
> Maciej Tomaszczyk<BR>
> Polish Geological Institute<BR>
> Geological Mapping Department<BR>
><BR>
><BR>
><BR>
<BR>
<BR>
<BR>
</FONT>
</P>
</BODY>
</HTML>