[GRASSLIST:8871] Add perimeter length to table

David Finlayson david.p.finlayson at gmail.com
Thu Nov 3 22:26:39 EST 2005


In short I want to add the perimeter length of my vector
areas/boundaries/shapes (whatever they are called) to the dbf table. I
was able to add the area with v.to.db, but I am confused on how to do
the perimeter.

In long, I am completely confused by the vector object model and I
haven't been able to find a good explanation on the web (I probably
missed it). Here are a few of my questions:

1) What is the format of the vector file on disk (geometry, attributes, etc.)
2) What do grass terms like point, line, centroid, boundary, area,
etc. mean exactly. Are they used consistently throughout the manuals?
3) What are the difference between categories and attributes (exactly)?
4) What are layers?
5) How much of SQL is implemented in GRASS (presumably for dbf
support) and how much is assumed from the back end (PostGRES, MySQL,
etc.)?

I could go on, for example the relationship of the SQL commands (db.*)
to each other, the man page for v.to.db seems completely opaque to me.

I feel like I missed a few weeks of class somewhere! That being said,
it looks to me like the new vector model is not as well documented as
the raster side of things.

David

--
David Finlayson
Marine Geology & Geophysics
School of Oceanography
Box 357940
University of Washington
Seattle, WA  98195-7940
USA

Office: Marine Sciences Building, Room 112
Phone: (206) 616-9407
Web: http://students.washington.edu/dfinlays




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