1v.build.polylines(1)          Grass User's Manual         v.build.polylines(1)
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NAME

6       v.build.polylines  - Build polylines from lines.
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KEYWORDS

9       vector, topology
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SYNOPSIS

12       v.build.polylines
13       v.build.polylines help
14       v.build.polylines [-q] input=string output=string  [--overwrite]
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16   Flags:
17       -q  Run quietly
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19       --overwrite
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21   Parameters:
22       input=string
23           Input binary vector map
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25       output=string
26           Output vector map
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DESCRIPTION

29       v.build.polylines  builds  polylines  from the lines in a binary vector
30       file.
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32       A line is a single straight line segment defined by one start node, one
33       end  node  and  no other nodes. A polyline is also defined by one start
34       node, one end node and no other nodes, but is made of two or more  con‐
35       secutive  straight  line  segments.  The  connections  between the con‐
36       stituent line segments of a polyline do not appear as nodes in the vec‐
37       tor map.
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39       Polylines  provide  the most appropriate representation of curved lines
40       when it is important that nodes serve to define  topology  rather  than
41       geometry.  Curved  lines  are usually digitized as polylines, but these
42       are sometimes broken into their constituent straight line segments dur‐
43       ing  conversion  from one data format to another. v.build.polylines can
44       be used to rebuild such broken polylines.
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NOTES

47       If the lines that make up a  polyline  are  of  different  types,  then
48       v.build.polylines  will  set  the type from the first constituent line.
49       v.build.polylines  will issue a warning unless the  flag  -q  has  been
50       set.  It is possible to keep a list of all such warnings by redirecting
51       standard output to a file.
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53       If the lines that make up a polyline have  different  attribute  values
54       then  v.build.polylines will set the attribute value of the polyline to
55       that of the last line  (this is the behaviour of v.build, which is used
56       to assign the attribute values).
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58       v.build.polylines  correctly  handles input maps containing lines, area
59       edges and points. Lines and area edges will be converted  to  polylines
60       of  the desired type.  Areas are only guaranteed to be preserved if the
61       constituent lines of the polylines that define them are all area  edges
62       in the input map.
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ACKNOWLEDGEMENTS

65       This program was originally written during Mark Lake's tenure of a Lev‐
66       erhulme Special Research Fellowship at University College London.
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SEE ALSO

69        v.build
70       v.in.ascii
71       v.split
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AUTHORS

74       Mark Lake, Institute of Archaeology, University College London.
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76       Major rewrite by Radim Blazek, October 2002
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78       Last changed: $Date: 2005/10/13 15:59:46 $
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80       Full index
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84GRASS 6.2.2                                               v.build.polylines(1)
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