# [GRASSweb-list]markus: web/grass51/tutorial examples.html,1.14,1.15

grass at intevation.de grass at intevation.de
Mon Feb 10 08:18:28 EST 2003

Author: markus

Update of /grassrepository/web/grass51/tutorial
In directory doto:/tmp/cvs-serv18822

Modified Files:
examples.html
Log Message:
cosmetics here and there

Index: examples.html
===================================================================
RCS file: /grassrepository/web/grass51/tutorial/examples.html,v
retrieving revision 1.14
retrieving revision 1.15
diff -u -d -r1.14 -r1.15
--- examples.html	9 Feb 2003 20:07:42 -0000	1.14
+++ examples.html	10 Feb 2003 13:18:26 -0000	1.15
@@ -177,13 +177,14 @@
<DIV ALIGN=right><a href="#toc">[UP]</a></DIV>
</b></big></font></td></tr></table>

-[for this exercise we use the Spearfish data set from the GRASS web site]
+[for this exercise we use the Spearfish data set from the GRASS web site]<br>
+[The WATRTOWR.DXF can be found <a href=http://www.3dcafe.com/asp/architex.asp#DXF>here</a>]
<P>
Since GRASS 5.1 supports 3D vector data, we can easily import DXF and DWG
files and display them with NVIZ:

<div class="code"><pre>
-v.in.dwg in=WATERTOWER.DXF out=watertowerXY
+v.in.dwg in=WATRTOWR.DXF out=watertowerXY
</div></pre>

The topology should be build for 'faces' which are (filled) 3D vector
@@ -209,6 +210,7 @@
r.mapcalc "dem_flat=-1874"
nviz el=dem_flat vect=watertowerXY
</div></pre>
+<P>

<b>Transformation to UTM coordinates:</b>
<P>
@@ -216,7 +218,7 @@
a national grid, we can use 'v.transform' with a 4 point transformation.
We select UTM coordinates where to place the water tower and query the
elevation (d.what.rast elevation.dem). We decide that the xy-extension of
-the watertower be 20m and it's height 100m (defined later).<br>
+the water tower be 20m and it's height 100m (defined later).<br>
The required transformation points file for 'v.transform' may look like this
(L: left, R: right, U: upper, L: lower, N, S, W, E):

@@ -243,8 +245,8 @@
The 'zshift' parameter is used to shift the object vertically on top of the
elevation model (use the bottom 'B' value shown by 'v.info' and add the
local elevation). The '-t' flag automatically shifts the DXF/DWG object(s)
-to sea level which is useful if the vector objects were drawn with negative
-z values:
+to sea level which is useful if the vector objects were composited with
+partially negative z values:

<div class="code"><pre>
v.transform -t in=watertowerXY out=watertowerUTM points=wt.points zscale=0.04 zshift=1320
@@ -252,7 +254,7 @@
nviz el=elevation.dem vect=watertowerUTM
</div></pre>

-You will have to zoom heavily to find the watertower as it appears to
+You will have to zoom heavily to find the water tower as it appears to
be very small compared to the surrounding mountains.

@@ -660,11 +662,12 @@
END
</div></pre>

-And here you can see how it looks like: <a
-href=http://grass.itc.it/cgi-bin/mapserv?map=/var/www/map-script/mapserverjs.map&layer=dem>Online MapServer
+And here you can see how it looks like: <br>
+<a href=http://grass.itc.it/cgi-bin/mapserv?map=/var/www/map-script/mapserverjs.map&layer=dem>Demo Online MapServer
reading GRASS raster, SHAPE, GeoTIFF and PostGRASS/PostGIS data</a>

+<P>

Since we still have the geometry and attributes in different tables, we
can add a 'view' onto both tables (sort of virtual table merging both).
@@ -717,14 +720,15 @@
using d.path.

As the column 'travelcost' is not yet present in the table 'road' we can use
-StarOffice or OpenOffice to add it (see <a href=attrib_storage>here</a>).
+StarOffice or OpenOffice to add it (see <a href="attrib_storage.html#toc">here</a>).
The we can continue and insert values according to the road type (be sure to
quote strings when using for where statement):

<div class="code"><pre>
echo "select * from roads" | db.select
</div></pre>
-... shows the travelcost column filled with 0.0.
+... shows that the travelcost column is filled with 0.0. To assign
+new travel costs, we run:<br>

<div class="code"><pre>
echo "update roads set travelcost=5 where cat=1" | db.execute
@@ -735,9 +739,14 @@
echo "select * from roads" | db.select
</div></pre>

+Then we can run the 'd.path' with our assigned travel costs:
<div class="code"><pre>
</div></pre>
+
+To see the forward directions of the vector lines, use the 'dir' for the
+'display' parameter in 'd.vect'. It will add small arrows indicating the
+forward directions when plotting the vector map.

<hr>
<P>