Mapping Hacks

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Chapter 6, Mapping on Your Desktop

#74 Plot Wireless Network Viewsheds with GRASS

HACK

Next, we can display these points, and then label them, with the following

commands:

GRASS:~/hacks/viewshed > d.vect nodes display=shape \

icon=basic/box color=blue

GRASS:~/hacks/viewshed > d.vect nodes display=attr attrcol=str_1 \

lcolor=blue bgcolor=white xref=left yref=bottom

The display=attr option to d.vect instructs it to display shape attributes,

rather than the shapes themselves. In GRASS 5.7, every shape in a vector

layer is potentially associated with a row of attributes—labels, statistics, and

so on—stored in data tables inside GRASS. We don’t really have the space

to get into why v.in.ascii put the labels into an attribute column with the

unimaginative title of

str_1, but if you’re interested, try running v.info -c

nodes

, and possibly echo "select * from nodes" | db.select (really!) to see

how this sort of thing works under the hood.

In versions prior to GRASS 5.7, point data was stored in sep-

arate site layers, rather than as vector layers containing

points. If you’re running an older version of GRASS, you’ll

need to use the following commands instead:

GRASS:~/hacks/viewshed > s.in.ascii sites=nodes \

in=sites_utm.txt

GRASS:~/hacks/viewshed > d.sites nodes color=blue \

type=box

GRASS:~/hacks/viewshed > d.site.labels nodes \

color=blue back=white xref=left yref=bottom

Consult the manpages for each of