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NAME - Builds polylines from lines or boundaries.


vector, geometry, topology

SYNOPSIS help [-q] input=name output=name [cats=string] [--overwrite] [--verbose] [--quiet]


Do not print polyline info
Allow output files to overwrite existing files
Verbose module output
Quiet module output


Name of input vector map
Name for output vector map
Category number mode
Options: no,first,multi
Default: no
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

DESCRIPTION builds polylines from the lines or boundaries in a vector map.

A line is a single straight line segment defined by one start node, one end node and no other nodes. A polyline is also defined by one start node, one end node and no other nodes, but is made of two or more consecutive straight line segments. The connections between the constituent line segments of a polyline do not appear as nodes in the vector map.

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. can be used to rebuild such broken polylines.


If the lines that make up a polyline are of different types, then will set the type from the first constituent line.

Category number(s) are assigned to a polyline based on cats parameter. correctly handles input vector maps containing lines, boundaries, centroids and points. Lines and boundaries will be converted to polylines of the desired type. Areas are only guaranteed to be preserved if the constituent lines of the polylines that define them are all boundaries in the input vector map.


This program was originally written during Mark Lake's tenure of a Leverhulme Special Research Fellowship at University College London.

SEE ALSO,, v.split, v.edit


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

Last changed: $Date: 2007-10-10 04:49:16 -0700 (Wed, 10 Oct 2007) $

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