[GRASS-user] Line of Sight/Viewshed help

[Dan Connors]

A cell phone provider wants to install a cell tower in our neighborhood along
a protected ridgeline.  I am working with some of the neighbors to see what
options our town has to regulate the location of the tower.  I have been
trying to learn the GRASS system and volunteered to produce a map that will
show from where the proposed tower will be seen.  I know the proposed
location (lat/long) and height of the tower.

I have been running some of the examples in the GRASS book (Open Source
GIS:AGrass GIS Approach, 3rd Edition) for line-of-sight calculations (eg,
page 152) and can get the examples to work for the NC sample data and the
spearfish data.  

I downloaded elevation data from the USGS (1/3 arc second resolution), but I
can't get r.los to work on this data because it is lat/long based and r.los
requires XY data.  I see there is an add-on module, r.viewshed which can
take lat/long coordinates as input.  I guess I could also re-project the
elevation data.

Can someone suggest what map data, what projection, and which module (r.los
or r.viewshed) I should use?  My goal is to produce a map like that on page
152 showing the area in my neighborhood.  I think I understand the basic
concepts but I need some guidance to pull the right pieces together.

Thank you for your help.

Dan


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