[GRASSLIST:3338] Re: help

Benjamin Ducke benducke at compuserve.de
Mon May 3 17:03:45 EDT 2004

Hallo Chet,

I am an archaeologist and have been working with GRASS for about 6 or 7 years now.
To flatten your learning curve, I will give a (very) short summary of what
I think GRASS GIS is good for in archaeology:

- GRASS has a lot of analytical functionality for raster maps (integer, i.e.
  categorised data and floating points, i.e. metric measurements)
- you can easily create knew functionality by combining the inputs and outputs
  of modules using shell scripts. If you know C, there is no limit to what you
  can do
- GRASS up to version 5.3 is very limited when it comes to advanced vector
  capabilities. This is changing for the better as work on 5.7 progresses
- GRASS has very limited CAD functionality. It's not a good choice for editing
  your own vector maps
- GRASS is great for pulling in data from all sorts of different sources, rasterising
  it, running your analyses and outputing it to another format for publication

Now, where would your sort of work fit into this?
Plotting and processing geophysical data is possible
through GRASS' excellent support of floating point raster maps.
You can easily:
- import measurements in regular grids from ASCII-data (r.in.ascii, or s.in.ascii, then
  pass it on to e.g. s.surf.rst to create an interpolated raster)
- build nice colortables to make measurements more easily interpretable
  (easiest way of doing this is by editing color tables directly. See GRASS5 programming manual)
- patch different grids together (r.patch)
- use neighbourhood functions to smooth out data
  (r.neighbors although I am not aware of a dedicated low or high pass filter)
- use map-algebra to implement any other sort of filters
  (r.mapcalc -- if you know the math -- I certainly don't)
- interpolate missing data points (e.g. r.surf.idw)
- handle NULL data values
- drap data over a digital terrain model (nviz)
- export to tons of raster formats (r.out.*)

... plotting several types of archaeological material
Well, what sort of plots are you thinking about?
I assume you are planning to do plots of site/artefact distributions over some
sort of map data. It's easy to get the coordinates of your things
into GRASS by using s.in.ascii. You can then do very basic plots using s.display.
Look into ps.map manual pages to find out how to do more visually
pleasing stuff. 
But really, if you are planning to do statistical plots,
use the GRASS-R interface to pull your data into the R statistical
programming environment (www.r-proj.org) and you have a system that
covers EVERY imaginable aspect of plotting/statistics.

I have never come across a tutorial that deals with GRASS and archaeological
data, but I recommend you to download at least the spearfish dataset from
the GRASS homepage. If you know German, go to http://grass.itc.it/gdp/handbuch/
and download Markus Neteler's excellent handbook ;)

Hope this will help you on your rough road to GRASS enlightenment.



On Mon, 3 May 2004 11:11:59 -0500
Chet Walker <chetwalker at mail.utexas.edu> wrote:

> Hello.
> I am new to GRASS, GIS and UNIX . . . . as you would expect i'm 
> having learning curve issues.  I'm trying to use grass for my 
> dissertation that entails very basic things like plotting several 
> different types of archaeological materials as well as a bit more 
> advanced issues such as plotting and processing geophysical data 
> (collected with a magnetometer and conductivity meter).  I have read 
> Neteler and Mitasova's book on GRASS and consulted several online 
> tutorials and faq's.  Does any one happen to know of a tutorial or 
> faq specifically targeted for archaeologists or perhaps know of a 
> general introduction course on GRASS?
> Thank you much,
> Chet Walker
> ________________________________________
> Chet Walker	312.857.7629
> Research Assistant
> Department of African and Amerindian Art
> The Art Institute of Chicago
> -- 

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