[GRASSLIST:207] Re: Coastline and category confusion

[H Bowman]

> Now my other question: the coastline, or the contour with elevation
> zero. I've digitized contours and coastline and I want to create a
> DEM. But I can't figure out how to specify that a contour has
> elevation zero.

You can't have a category 0, and v.to.rast works on category.
I think this is v.to.rast's fault - it should really give you the option
to take the value from the label, not the cat #, as s.to.rast does.

All the internal conversion programs seem to work on a different
convention.. some need labels to work, some work on attributes, etc.
It's a bit confusing and frustrating sometimes. Hopefully GRASS 5.1 will
fix this.

What I've done is put the coastline in as 2 in the vector, and then
use a r.mapcalc command to put things right once it is in.

Mind that the coastline is actually at zero though. Different data sets
use different conventions for what it is. (mean sea level, high-high
water, mean-high water, traced from a aerial photo[ie mean on average],
etc).


Hamish