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Geografic-Information-System


			
				
					
						
						
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<title>GRASS 5.7/6 Vector Format and API</title>
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<p><H1>GRASS 5.7/6 Vector Format and API</H1>

The API is described in
<p><a href="http://grass.itc.it/devel/index.php#prog">GRASS 6 Programmer's Manual</a>
<p>
source code file:<br>
lib/vector/vectorlib.dox

<HR>

<h2><A NAME="ascii">Vector ASCII Format Specification</a></h2>
<p>
<i>format notes here are outdated and to be merged into<br>
vector/v.in.ascii/description.html</i>

<p>The ASCII format in the new version contains support for categories,
z-coordinates, and the new types centroid, face, and kernel.
Points and centroids are saved as one coordinate pair instead of two.
File is saved in old dig_ascii directory but the name will be probably changed.

<h3>Head</h3>
The head of the file is similar as the head file of vector binary
format but contains bounding box also. Key words are:<br>
<pre>
ORGANIZATION
DIGIT DATE
DIGIT NAME
MAP NAME
MAP DATE
MAP SCALE
OTHER INFO
ZONE
WEST EDGE
EAST EDGE
SOUTH EDGE
NORTH EDGE
MAP THRESH
</pre>

<h3>Body</h3>
The body begins with the row:
<pre>
VERTI:
</pre>
followed by records of lines:
<pre>
TYPE NUMBER_OF_COORDINATES [NUMBER_OF_CATEGORIES]
 X Y [Z]
....
 X Y [Z]
[ FIELD CATEGORY]
....
[ FIELD CATEGORY]
</pre>

Everything above in <b>[ ]</b> is optional.
Note the coordinate order in the old version (Y X) has been changed
to (X Y [Z]).
<br><br>

TYPE may be:<br>
<ul>
<li><b>P</b> point (dot) <br> 
<li><b>p</b> dead point (dead dot) <br> 
<li><b>L</b> line  <br>
<li><b>l</b> dead line <br> 
<li><b>B(A)</b> boundary  <br>
<li><b>b(a)</b> dead boundary  <br>
<li><b>C</b> centroid  <br>
<li><b>c</b> dead centroid  <br>
<li><b>F</b> face (3D boundary) <br>
<li><b>K</b> kernel (3D centroid) <br>
</ul>

<br>
Example of records:
<pre>
P 1 1
 1234 3435
 1 354
L 3 1
 4132 4534
 1453 1454
 1453 4543
 1 355
</pre>

<HR>
<h2><A NAME="example">Vector module programming example</a></h2>

<a href=v.example/>Vector module C programming example</a>

<h2><A NAME="status">Vector module upgrade status</a></h2>

<a href=v.modules.html>Vector upgrade status</a> (partially outdated)

<hr>
$Date$
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