[GRASS-user] New User

Thomas D. Dean tomdean at speakeasy.org
Mon Feb 28 13:28:51 EST 2011

On Sun, 2011-02-27 at 23:25 -0800, Hamish wrote:

I know little or nothing about mapping.  I want to understand how the
data files and grass connect together.  Some tutorial using known data
followed by some information on various data formats and how to convert
them into something GRASS can handle

> Could you explain your workflow a bit more? there are many
> choices.   In general it's not so bad, and you can do matlab/oct
> to and from grass without much hassle.

I have data consisting of bearings amd/or distances from known points,
in octave.  I want to plot the bearing lines and the distance arcs on a
wgs84 ellipsoid with national boundaries (outlines).  The end result is
to visually locate the intersections of the various lines with national
outlines for easier identification of RF sources.

> natural earth is polyline data, so vector & thus v.* modules.
> 2D array is raster data, so r.* modules.
> see v.to.rast and r.to.vect modules.

The data from natural earth is
10m_admin_0_countries.dbf - spreadsheet database file
10m_admin_0_countries.prj - projection
10m_admin_0_countries.shp - shape file

I also have WDB data from


I have not discovered how to bring the map data into grass.  How do I
arrange the data files so GRASS can find/inport them?  I have a
$home/grassdata directory structure with worldlocation.tar.gz expanded
into it as $home/grassdata/worldlocation.  How do I access/plot this
data in GRASS?

How do I put the ETOPO5 data in the grassdata tree?  I think I need to
convert it to some format that GRASS understands.

How do I put the 10m_admin_0_countries.* files into the grassdata tree?

> do you have 2D arrays in matlab/octave from contourf() or similar
> and you want to fill(), area(), or patch() a polygon coastline
> over the top?

I have these in octave 3.4.0.

> see  http://grass.osgeo.org/wiki/Addons#v.out.ascii.mat
> are you using the (free/gratis) m_map toolbox?
>   http://www.eos.ubc.ca/~rich/map.html
> or matlab's mapping toolbox? (which is using proj4, same as us)
> do you wish to rasterize the natural earth polygons into a 2D
> array?
> see v.to.rast + r.out.mat
> do you want to bring your matlab data into grass and plot it
> there?
> see r.in.mat, or v.in.lines, v.in.mapgen.

This would be Ok, assuming I can export the resulting map in pdf format.
My first thought was to use GRASS to generate a MAT file from map data,
to load into octave.

> the first step is to bring the data into grass with v.in.ogr.

I can start grass and get the startup screen.  I select worlddata and
PERMANENT and click Enter GRASS.  What is next?


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