Hi,
usually I am working raster-oriented, so I have questions
concerning snapping nodes in v.digit:
When digitizing a polygon (with mouse digitizer), how to
make the end nodes of a polygon to be snapped automatically?
Changing the snapping distance didn't help (and using always
the Edit menu is a ot of extra work). What did I miss?
I need the polygons to be closed.
Markus
Marcus,
On your digitizing menu, be sure to select type "area edge" (hit the "t"
key to select it). Maybe you were digitizing lines instead of areas. And
of course, create your last node on top of your first node, then right
click to stop digitizing. We use a digitizing threshold of .005 (which
will affect stream digitizing with a tablet) and a snapping threshold of
.01 . This works well for us.
Good luck!
Katie
Markus Neteler wrote:
Hi,
usually I am working raster-oriented, so I have questions
concerning snapping nodes in v.digit:When digitizing a polygon (with mouse digitizer), how to
make the end nodes of a polygon to be snapped automatically?
Changing the snapping distance didn't help (and using always
the Edit menu is a ot of extra work). What did I miss?
I need the polygons to be closed.Markus
--
Katie Alvin
FOCS/FGI/GIS Specialist
USDA NRCS, Bozeman, MT
(406)587-6929
kalvin@mt.nrcs.usda.gov
Hi, Markus
Changing the snapping threshold _should_ help. Don't forget that you're
working in "digitizer" inches - you'll need to multiply the threshold by
your scale to get equivalent ground distance.
If this still isn't helping, use the "snap to line" command in the Edit menu.
You can also specify a snapping threshold in v.support, though this is a
little risky. Save a backup copy before doing this, in case it snaps
lines that you didn't intend to!!
Best holiday wishes,
-Malcolm
On Wed, 23 Dec 1998, Markus Neteler wrote:
Hi,
usually I am working raster-oriented, so I have questions
concerning snapping nodes in v.digit:When digitizing a polygon (with mouse digitizer), how to
make the end nodes of a polygon to be snapped automatically?
Changing the snapping distance didn't help (and using always
the Edit menu is a ot of extra work). What did I miss?
I need the polygons to be closed.Markus
When digitizing a polygon (with mouse digitizer), how to
make the end nodes of a polygon to be snapped automatically?
Changing the snapping distance didn't help (and using always
the Edit menu is a ot of extra work). What did I miss?
I need the polygons to be closed.
Hi - (hi Malcolm and Katie),
you may remember this question. The reason for no-snapping
was that the vector map scale was set to 1:1.
When using a reasonable scale (1:25000) snapping works
fine.
Thanks
Markus
Hi all,
I try to digitize a soil map with v.digit. The areas, which lay side by side are
using the same line as a common border.
How do I manage to digitize these areas without digitizing each line a second
time for the adjacent areas? Can I snap one area with with another open area to
get two closed polygons?
Thanks in advance
Juergen Rogozia
Dear Juergen
When you are digitizing an areas map you don't need to repeat adjacent lines.
You must digitize the common border only one time, and snap the two nodes.
You can make you an idea with the attached image (sorry it's in spanish).
In all cases you must closed the area, normally opened nodes are green, and closed
nodes red, so you can easely find whats nodes are bad. You have the possibility to
snap automatically snap nodes with v.support.
Be carefull with this option, because you must check the right minimum distance
between two opened nodes.
If the distance is too large, v.support will snap all areas together.
I hope it'll help you
Juergen wrote:
Hi all,
I try to digitize a soil map with v.digit. The areas, which lay side by side are
using the same line as a common border.
How do I manage to digitize these areas without digitizing each line a second
time for the adjacent areas? Can I snap one area with with another open area to
get two closed polygons?Thanks in advance
Juergen Rogozia
--
Alexandre Rodier
INUAMA
Universidad de Murcia
Campus de Espinardo
30100 - MURCIA -
- SPAIN -
tel: -34 968.36.48.45
alexrod@fcu.bio.um.es
Am Wed, 20 Jan 1999 schriebst Du:
Hi all,
I try to digitize a soil map with v.digit. The areas, which lay side by side are
using the same line as a common border.
How do I manage to digitize these areas without digitizing each line a second
time for the adjacent areas? Can I snap one area with with another open area to
get two closed polygons?Thanks in advance
Juergen Rogozia
Hi Juergen,
I did some digitizing with v.digit, but only with a mouse (don´t know what you
are using, but it shouldn´t make a big difference, in case you are using a
digitizer). Basically, you have to set a node at all the points, where lines
of the two polygons join to a single one. Just quit digitizing the line
at this point and start the new ones at it (this takes always four mouseclicks,
but you get used to it). If you want to join a line you are currently
digitizing, let it end on the node. Before you start digitizing, adjust a decent
snapping threshold (Customize Menu), that the lines are joining properly.
If you forgot to set a node, use ´break a line´ in the Edit Menu. In case a
line didn´t join properly with a node, correct it afterwards with ´Snap Line to
Node´ in the same menu. It might help to solve your second problem as well.
Using v.digit, you have to become a sort of keyboard DJ (never understood the
idea of using capital letters to open the menus), but after a while it´s okay
and you can digitize pretty fast. A copy of the ´GRASS 4.0 Map Digitizing
Manual: v.digit´ would be handy, if you don´t have it at all. you can get it
from: http://www.geog.uni-hannover.de/grass/
It´s part of the documentation package and perhaps you get it seperatly as well.
Best wishes
Rainer