- Builds polylines from lines or boundaries.
vector, topology, geometry, line, node, vertex
Allow output files to overwrite existing files
Print usage summary
Verbose module output
Quiet module output
Force launching GUI dialog
- input=name [required]
Name of input vector map
Or data source for direct OGR access
- output=name [required]
Name for output vector map
Category number mode
Options: no, first, multi, same
no: Do not assign any category number to polyline
first: Assign category number of first line to polyline
multi: Assign multiple category numbers to polyline
same: Create polyline from lines with same categories
Input feature type
Options: line, boundary
builds polylines from the lines or boundaries in a
A line is defined by one start node, one end node and any number of vertices
between the start and end nodes. The shortest possible line consists of only
two vertices where the coordinates of the start and end nodes are identical to
those of the two vertices.
picks a line and from its start node, walks back as
long as exactly one other line of the same type is connected to this node.
Line directions are reversed as required, i.e. it does not matter if the next
line is connected to the current node by its start or end node. Once the start
line of a polyline is identified, it walks forward and adds all vertices (in
reverse order if needed) of connected lines to the start line, i.e. the start
line and connecting lines are reversed as needed. That is, if a line is
reversed depends on what node is initially picked for building polylines. If
the direction of lines is important (it’s not for boundaries to build
areas), you have to manually change line directions with either v.edit
or the wxGUI vector digitizer
Polylines provide the most appropriate representation of curved lines when it is
important that nodes serve to define topology rather than geometry. Curved
lines are usually digitized as polylines, but these are sometimes broken into
their constituent straight line segments during conversion from one data
format to another. v.build.polylines
can be used to rebuild such broken
combines only lines of the same type to a new polyline,
i.e. lines and boundaries are kept separate.
Category number(s) are assigned to a polyline based on cats
- cats=no - No category number is assigned to a polyline. Also
attributes tables linked to the input vector map are not copied to the
output vector map.
- cats=first - Assign to a polyline category number of the first
line. All linked attributes tables are copied to the output vector map
without filtering, but the categories are processed according to the cats
- cats=multi - If the lines that make up a polyline have different
category numbers then v.build.polylines will set the multiple
category numbers to a polyline. Also all linked attributes tables are
copied to the output vector map.
- cats=same - Assigned lines to a polyline have same category numbers
in all layers. Linked attributes tables are copied to the output vector
correctly handles input
vector maps containing
lines, boundaries, centroids and points. Lines and boundaries will be
converted to polylines. Areas are guaranteed to be preserved.
This program was originally written during Mark Lake’s tenure of a
Leverhulme Special Research Fellowship at University College London.
v.build, v.in.ascii, v.edit, v.split
Mark Lake, Institute of Archaeology, University College London.
Major rewrite by Radim Blazek, October 2002
Category mode added by Martin Landa, FBK-irst, Trento, Italy, October 2007
Support for categories, attributes, and different line types by Markus Metz
Last changed: $Date: 2017-02-15 23:17:07 +0100 (Wed, 15 Feb 2017) $
Available at: v.build.polylines source code (history)
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