[GRASSLIST:2050] editing raster polygon

GRASS GRASS user
1

I have a complex raster polygon that I use as a mask. I need to edit the polygon. Specifically, I need to remove some areas of the polygon.

I have used r.digit to digitize the areas that I would like to remove, but I can not seem to see what to do next.

Thanks.

Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich <at> GreenwoodMap <dot> com
(307) 733-0203
http://www.GreenwoodMap.com

2

Convert the digitized polygon areas to raster and use r.mapcalc.
correctedpolygon= if(areastoremove,NULL(),uncorrectedpolygon)

(Please refer the r.mapcalc manual for the syntax)

Helmer

Richard Greenwood wrote:

I have a complex raster polygon that I use as a mask. I need to edit the polygon. Specifically, I need to remove some areas of the polygon.

I have used r.digit to digitize the areas that I would like to remove, but I can not seem to see what to do next.

Thanks.

Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich <at> GreenwoodMap <dot> com
(307) 733-0203
http://www.GreenwoodMap.com

--
Dr.Helmer Schack-Kirchner
Institut für Bodenkunde und Waldernährungslehre
Albert-Ludwigs-Universität
79085 Freiburg / Germany
Tel. xx761 203 3612
Fax. xx761 203 3618

3

Helmer,

Thank you very much. You put me on the right path. I made two minor changes (below) to your approach and got the result that I desired.

     r.mapcalc
     correctedpolygon=if(not(isnull(areastoremove)), null(), uncorrectedpolygon)

I appreciate your help.
Thanks,
Richard

At 08:14 AM 12/15/2003, Helmer Schack-Kirchner wrote:

Convert the digitized polygon areas to raster and use r.mapcalc.
correctedpolygon= if(areastoremove,NULL(),uncorrectedpolygon)

(Please refer the r.mapcalc manual for the syntax)

Helmer

Richard Greenwood wrote:

I have a complex raster polygon that I use as a mask. I need to edit the polygon. Specifically, I need to remove some areas of the polygon.

I have used r.digit to digitize the areas that I would like to remove, but I can not seem to see what to do next.

Thanks.

Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich <at> GreenwoodMap <dot> com
(307) 733-0203
http://www.GreenwoodMap.com

--
Dr.Helmer Schack-Kirchner
Institut für Bodenkunde und Waldernährungslehre
Albert-Ludwigs-Universität
79085 Freiburg / Germany
Tel. xx761 203 3612
Fax. xx761 203 3618

Richard W. Greenwood, PLS
Greenwood Mapping, Inc.
Rich <at> GreenwoodMap <dot> com
(307) 733-0203
http://www.GreenwoodMap.com