[GRASS-user] Help needed in creating a thematic map

Markus Neteler neteler at osgeo.org
Sat Mar 21 16:08:44 EDT 2009


On Sun, Mar 8, 2009 at 4:03 AM, Thomas Adams <Thomas.Adams at noaa.gov> wrote:
> List:
> I need to create a map in GRASS like the attached map. This needs to be done
> on a daily basis, and it needs to be created by those who have little GIS or
> GRASS knowledge or experience. The critical aspect is to manually
> draw/digitize the critical "likely" or "possible" areas. And I am struggling
> with v.digit doing this, but it's not the main problem.

(which v.digit do you use?)
Perhaps Featureserver would be a good idea here:

(random demo: http://dev.riverchange.org/featureserver/
 use the + at top right to activate WMS
 SHIFT-left-mouse-button to zoom in via box

Or the new digitizer in GRAS 6.4:
-> New vector digitizer tool with advanced editing features

> The key issue is
> attaching attribute data to the polygonal regions that define the period
> over which the "likely" or "possible" areas apply, as the graphic shows.

Both Featureserver and GRASS digitizer support this.

> ALSO, the boundary data and the attributes (the valid Date period) need to
> be exported to an ascii text file which is then ftp'ed to a central location

(new) v.out.ascii export attributes in point mode. You could export
the ASCII data in "standard" format, then convert centroids to points
and in a second run of v.out.ascii export attributes.

> — the end users use their own software to combine other such files to create
> a graphic (actually the one I am showing). Now, combining the exported data
> into the format needed by the end user is not an issue,

At this point I would export SHAPE format which includes the attributes
in the DBF table.

> it's really a matter
> of how to most efficiently (easily) get the Starting and Ending dates into
> the attributes of the polygons.

I would just use two columns in the attribute table.

> Also, should I try to use a separate vector
> map for each polygon of the same type ("likely" or "possible") or should
> they be in different layers?

IMHO yes.

> I'll have to write detailed instructions covering how to do this, but I need
> to know how to do this first!
> I'm very open to suggestions…

Hope this helps,

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