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<FONT FACE="Verdana, Helvetica, Arial"><SPAN STYLE='font-size:12.0px'>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:<BR>
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Case 1 – no existing vector:<BR>
-Use GUI/display to create onscreen vector object<BR>
-Output vector object to sequence of xy coordinate pairs with relevant topological, key field (cat), and vector type information<BR>
-Input xy coordinates along with other information into v.edit to create vector<BR>
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Case 2 – existing vector to be edited:<BR>
-Output sequence of xy coordinate pairs with relevant topological, key field (cat), and vector type information from existing vector<BR>
-Read xy and related information into GUI to create on-screen vector object<BR>
-Use GUI/display to edit onscreen vector object<BR>
-Output vector object to sequence of xy coordinate pairs with relevant topological, key field (cat), and vector type information<BR>
-Input xy coordinates along with other information into v.edit to create vector<BR>
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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. <BR>
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So in addition to v.edit, we’ll 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.<BR>
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Michael<BR>
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Michael Barton, Professor of Anthropology<BR>
School of Human Evolution & Social Change <BR>
Center for Social Dynamics & Complexity<BR>
Arizona State University<BR>
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phone: 480-965-6213<BR>
fax: 480-965-7671<BR>
www: <a href="http://www.public.asu.edu/~cmbarton">http://www.public.asu.edu/~cmbarton</a> <BR>
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