1v.build.polylines(1) Grass User's Manual v.build.polylines(1)
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6 v.build.polylines - Builds polylines from lines or boundaries.
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9 vector, geometry, topology
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12 v.build.polylines
13 v.build.polylines help
14 v.build.polylines [-q] input=name output=name [cats=string] [--over‐
15 write] [--verbose] [--quiet]
16 Flags:
18 -q
19 Do not print polyline info
20 --overwrite
22 Allow output files to overwrite existing files
23 --verbose
25 Verbose module output
26 --quiet
28 Quiet module output
29 Parameters:
31 input=name
32 Name of input vector map
33 output=name
35 Name for output vector map
36 cats=string
38 Category number mode
39 Options: no,first,multi
40 Default: no
41 no: Do not assign any category number to polyline
42 first: Assign category number of first line to polyline
43 multi: Assign multiple category numbers to polyline
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46 v.build.polylines builds polylines from the lines or boundaries in a
47 vector map.
48 A line is a single straight line segment defined by one start node, one
50 end node and no other nodes. A polyline is also defined by one start
51 node, one end node and no other nodes, but is made of two or more con‐
52 secutive straight line segments. The connections between the con‐
53 stituent line segments of a polyline do not appear as nodes in the vec‐
54 tor map.
55 Polylines provide the most appropriate representation of curved lines
57 when it is important that nodes serve to define topology rather than
58 geometry. Curved lines are usually digitized as polylines, but these
59 are sometimes broken into their constituent straight line segments dur‐
60 ing conversion from one data format to another. v.build.polylines can
61 be used to rebuild such broken polylines.
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64 If the lines that make up a polyline are of different types, then
65 v.build.polylines will set the type from the first constituent line.
66 Category number(s) are assigned to a polyline based on cats parameter.
68 cats=no - No category number is assigned to a polyline.
70 Also attributes tables linked to the input vector map are
71 not copied to the output vector map.
72 cats=first - Assign to a polyline category number of the
74 first line. All linked attributes tables are copied to
75 the output vector map.
76 cats=multi - If the lines that make up a polyline have
78 different category numbers then v.build.polylines will
79 set the multiple catetory numbers to a polyline. Also
80 all linked attributes tables are copied to the output
81 vector map.
82 v.build.polylines correctly handles input vector maps containing lines,
84 boundaries, centroids and points. Lines and boundaries will be con‐
85 verted to polylines of the desired type. Areas are only guaranteed to
86 be preserved if the constituent lines of the polylines that define them
87 are all boundaries in the input vector map.
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90 This program was originally written during Mark Lake's tenure of a Lev‐
91 erhulme Special Research Fellowship at University College London.
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94 v.build, v.in.ascii, v.split, v.edit
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97 Mark Lake, Institute of Archaeology, University College London.
98 Major rewrite by Radim Blazek, October 2002
100 Category mode added by Martin Landa, FBK-irst, Trento, Italy, October
101 2007
102 Last changed: $Date: 2007-10-10 13:49:16 +0200 (Wed, 10 Oct 2007) $
104 Full index
106 © 2003-2008 GRASS Development Team
108GRASS 6.3.0 v.build.polylines(1)