[GRASS-user] displaying many thematic maps from one vector dataset

[Vishal Mehta]

Hello all,

I am better at GRASS raster capabilities than with GRASS vector handling, so
I am writing to get your help.

What I want to do is this:
1. I will have one vector dataset of watersheds. Each record is a polygon,
an individual watershed. There are, apart from the usual cat fields, 52
attribute columns. Each attribute column is modeled weekly snow depth.

2. I need to automate the display and export to png of 52 thematic images -
one for each week/column - keeping the color scheme constant throughout.
Then all of the images will be packaged into a kml animation.

I know how to do the above starting from a stack of GRASS rasters, but am
not quickly getting a handle on displaying GRASS vectors consistently. I've
tried d.vect and d.vect.thematic. I havent tried d.thematic.area yet.

The main issues are that I dont know:
- how to assign a constant color scheme  to each map (that spans the min and
max of all columns); i guess i was looking for something as simple as
setting color rules like with raster data.

- how to refer to each attribute column by column number in a loop
(d.vect.thematic and d.thematic.area  seem to need column name as attribute)

Any pointers would be greatly appreciated,
Vishal

Vishal K. Mehta, PhD
Scientist
Stockholm Environment Institute - US
133 D St Suite F
Davis CA 95616
www.sei-us.org
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