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GRASS 5.1: Examples from US National Atlas
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<i><b>README:</b>
GRASS 5.1 is currently under development. It is neither complete (it still
contains only a few modules) nor it is intended for productional usage.
Development releases are provided for people who want to help test, debug,
and improve GRASS 5.1. Knowing this, please read on.</i><br>
<i>
These examples described here may work or not. You are kindly invited to
send us further examples and/or code bugfixes/enhancements.</i>
<p><table width="100%" cellpadding="3" border="0">
<tr><td align="left" bgcolor="#B0F0B0"><font color="#00000"><big><b>
<a name="overlay"></a>
Getting the data
<DIV ALIGN=right><a href="#toc">[UP]</a></DIV>
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In this section we want to play abit with the (new) GRASS vector capabilities. This section is
inspired by the paper
"<a href="http://www-users.cs.umn.edu/~djugash/cs8701/final.html">A Benchmark for Spatial
Database Teaching</a>" by Judy Djugash and Wei-Hsin Fu which focuses on the Open GIS Consortium's (OGC)
Simple Features Implementation Specification.
<P>
The data sets are available from the
<a href="http://nationalatlas.gov/mapit.html">National Atlas of the United States</a>, in
particular from the <a href="http://www.nationalatlas.gov/atlasftp.html">Map Layers Warehouse</a>
(this site is a dream for European GIS users).
<br>
We have to download following map layers:
<ul>
<li>Cities and Towns (Point data)
<li>States
<li>
<li>
<li>
<li>
<li>
</ul>
First we have to create a GRASS location in decimal degrees on datum NAD83:
<div class="code"><pre>
LOCATION: nationalatlas
mapset: user1
database: /usr/local/share/grassdata
Please specify the coordinate system for location <nationalatlas>
B Latitude-Longitude
Please enter a one line description for location <nationalatlas>
> nationalatlas
Do you wish to specify a geodetic datum for this location?(y/n) [y] y
Please specify datum name
>nad83
Now select Datum Transformation Parameters
>6
# 6 Used in Default nad83 region
DEFINE THE DEFAULT REGION
====== DEFAULT REGION =======
| NORTH EDGE:74:50N____ |
| |
WEST EDGE | |EAST EDGE
169:15E___ | |62:00W____
| SOUTH EDGE:13:20N____ |
=============================
PROJECTION: 3 (Latitude-Longitude) ZONE: 0
GRID RESOLUTION
East-West: 0:05______
North-South: 0:05______
</pre></div>
<P>
The data sets are provided in SHAPE format as well as SDTS format. GRASS can read both:
A) Import of "Cities and Towns" as SHAPE file:
<div class="code"><pre>
v.in.ogr dsn=citiesx020.shp output=cities
v.db.connect -p cities
d.vect cities icon=basic/circle fcolor=red
</pre></div>
One attribute table is connected to the geometry.
B) Import of "Cities and Towns" as SDTS file:
<div class="code"><pre>
v.in.ogr dsn=CITXCATD.DDF output=CITX
v.db.connect -p CITX
d.vect CITX icon=basic/circle fcolor=red
</pre></div>
Four attribute tables are connected to the geometry (accessible via 'field').
<P>
NOTE: Due to the map/tables size zooming before running a query with 'd.what.vect' is recommended.
<P>
We continue to work with the SHAPE files. Import of the "States" map:
<div class="code"><pre>
v.in.ogr dsn=statesp020.shp output=states
d.vect map=states fcolor=255:255:220
</pre></div>
<div class="code"><pre>
v.in.ogr dsn=statesp020.shp output=roads
d.vect map=roads where="FEATURE='Limited Access Highway Toll Road' or FEATURE='Limited Access Highway'" col=blue
</pre></div>
<P>
The maps imported so far look like this:<br>
<a href=images/usa_nationalatlas.png><DEFANGED_IMG src=images/usa_nationalatlas_small.jpg alt="GRASS USA National Atlas example"></a>
<P>
Ex 1) List the name and area of all the states that are adjacent to Minnesota in the State table.
<div class="code"><pre>
d.what.vect states
#see attribute table
v.extract input=states output=minnesota where=STATE='Minnesota'
TODO - implement touch operator
</pre></div>
Ex 2) List all the states that Interstate Route 90 passes through:
TODO - implementation of cross operator
<P>
Ex 3) List all the cities, which are within 150 km of the Interstate Route 90 road.
<div class="code"><pre>
d.vect map=roads where="NAME='Interstate Route 90' or NAME='Interstate Route 90, US Route 395'" col=green
#incomplete: we need a LIKE operator or =~
v.extract input=roads output=interstate90 field=1 new=0 where="NAME='Interstate Route 90' or NAME='Interstate Route 90, US Route 395'"
#check if buffer means geodetic dist in Lat/Long:
v.buffer input=interstate90 output=interstate90_150km buffer=150000 tolerance=1
TODO - implementation of cross operator
</pre></div>
<hr>
<P>
Further <a href=links.html>Links</a> (related software, SQL reference etc).
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<DIV ALIGN=right>© 2003 Markus Neteler<br>
<a href="mailto:weblist at grass.itc.it">Comments</a> about this page | <a href="../../faq/index.html">FAQ</a> | <a href="../../download.html">Download</a> | <a href="../../support.html">Support</a> | <a href="../../gdp/index.html">Docs</a> | <a href="../../grassdevel.html">Programming</a> | Back <a href=index.html>5.1 Tutorial Home</a><br>
<i>Last change:
$Date: 2003/08/19 16:17:25 $
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Index: index.html
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RCS file: /grassrepository/web/grass51/tutorial/index.html,v
retrieving revision 1.19
retrieving revision 1.20
diff -u -d -r1.19 -r1.20
--- index.html 14 Aug 2003 15:25:05 -0000 1.19
+++ index.html 19 Aug 2003 16:17:25 -0000 1.20
@@ -106,8 +106,9 @@
<li><a href="network.html#vnetsalesman">v.net.salesman</a>
</ol>
<li><a href="vectoroverlay.html">Vector overlay/clipping examples</a>
-
+ <li><a href="usa_demo.html">Examples from US National Atlas</a>
</ul>
+
<li><a href="troubleshooting.html">Troubleshooting</a>
<ol>
<li><a href="troubleshooting.html#sqlnames">The SQL query is rejected (parse error)!</a>
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