[GRASS-dev] V.edit and GUI digitizing

[Michael Barton]

Thinking about how to actually implement a better digitizing mode in GRASS
brought me back to some ideas that Glynn had a short time back. A schematic
workflow for digitizing might go like this:

Case 1 ­ no existing vector:
-Use GUI/display to create onscreen vector object
-Output vector object to sequence of xy coordinate pairs with relevant
topological, key field (cat), and vector type information
-Input xy coordinates along with other information into v.edit to create
vector

Case 2 ­ existing vector to be edited:
-Output sequence of xy coordinate pairs with relevant topological, key field
(cat), and vector type information from existing vector
-Read xy and related information into GUI to create on-screen vector object
-Use GUI/display to edit onscreen vector object
-Output vector object to sequence of xy coordinate pairs with relevant
topological, key field (cat), and vector type information
-Input xy coordinates along with other information into v.edit to create
vector

V.edit, as currently prototyped involves transforming a set of xy
coordinates into  vector objects. This is an important part of a digitizing
system, but not all of it. Because we will  also want to edit existing
vectors, there needs to be a way to transform vector objects into a set of
xy coordinates, while preserving any needed topological and key field
information to reconstruct them. In a discussion between Glynn and Radim
recently, it became clear that v.out.ascii does most of this, but not
all‹primarily lacking the topological information.

So in addition to v.edit, we¹ll need some kind of module to get relevant
vector information OUT of an existing vector, and into a format that can be
read by a GUI and v.edit. Along with this will need to be some kind of
standard format to preserve sufficient topological and other vector
information needed to reconstitute a GRASS vector. Such code is probably in
v.digit in some form.

Michael
__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton


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