[GRASSLIST:652] Extracting vector river network from r.terraflow.
Antonio G. - Geotronix
nightnavigator at libero.it
Tue Jul 8 10:04:53 EDT 2003
-----BEGIN PGP SIGNED MESSAGE-----
After trying r.flow and r.watershed to compute river networks over my
DEM I've finally tried r.terraflow with the 28/06 snapshot.
r.terraflow is finally giving a better stream network than the former
and this is visible by the flow accumulation raster layers.
However, what I need is a vector river network layer. I presume I have
to use the flow accumulation layer provided by r.terraflow as input but
I don't know how to process it. Must I use r.thin + r.line. But how? I
gave it a try but got errors from r.line:
GRASS:~ > r.line input=r.tf-7m-thin-accu output=v.tf-7m-thin-accu
update_list: crowded cell 8H (89,321)
ERROR: cell file is not thinned properly.
Please run r.thin
Maybe I have to reclass the categories?
BTW. The flow accumulation categories should express the amount of
water running through a cell? I saw the categories are rather
large 0 --> 631571. But what are they exacly expressing. If I get
a value of 631000 for a cell of a accumulation layer outputted by
r.terraflow, how must I interpret it?
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.2 (GNU/Linux)
-----END PGP SIGNATURE-----
More information about the grass-user