GRASS Vector Layers: Difference between revisions
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== Introduction == | == Introduction == | ||
Grass documentation provides basic information about vector attribute management. | |||
categories of vector features and vector layers. | |||
The aim of this tutorial is to show how to create, manipulate and | |||
display different layers of a vector using relational database. | |||
== Problem Description == | |||
An organization provides information about routes to be driven | |||
by drivers. The organization's database consists of | |||
* roads (road network) | |||
* routes driven on that roads | |||
Simple approach can be taken to present the routes to drivers. | |||
For every route a vector map could be created and overlayed over | |||
the road network vector, i.e. | |||
$ d.vect map=roads | |||
$ d.vect map=route01 color=green width=2 | |||
Above idea has a major flaw. If route data changes or new route is added | |||
then vector maps has to be regenerated. | |||
== Prepare Road Network == | == Prepare Road Network == | ||
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update road_network set id=cat; | update road_network set id=cat; | ||
http://grass.osgeo.org/grass63/manuals/html63_user/vectorintro.html |
Revision as of 20:10, 22 May 2008
Introduction
Grass documentation provides basic information about vector attribute management. categories of vector features and vector layers.
The aim of this tutorial is to show how to create, manipulate and display different layers of a vector using relational database.
Problem Description
An organization provides information about routes to be driven by drivers. The organization's database consists of
- roads (road network)
- routes driven on that roads
Simple approach can be taken to present the routes to drivers. For every route a vector map could be created and overlayed over the road network vector, i.e.
$ d.vect map=roads $ d.vect map=route01 color=green width=2
Above idea has a major flaw. If route data changes or new route is added then vector maps has to be regenerated.
Prepare Road Network
create table road_network (cat integer, id integer);
v.category --o in=roads out=outmap option=del
v.category --o in=outmap out=stepmap option=add
v.to.db map=setpmap option=cat
update road_network set id=cat;
http://grass.osgeo.org/grass63/manuals/html63_user/vectorintro.html