I'm sure that others have their own perspective but when I talk with someone familiar with Arc, who is thinking about using GRASS, I usually emphasize 2 things.
1. Although Arc has both vector and raster capabilities, most people who use it 'think vector' when they work with the GIS. It is often easier to convert to vector to work with geospatial data for many applications. GRASS is just the opposite. It has powerful vector tools, but for many applications it is easier to work in raster. So you need to 'think raster'.
2. Arc works like a word processor in that you can start the program without any data and then load various data files. Arc will attempt to overlay them by reprojecting on-the-fly. In other words, you don't need to know anything about your geospatial data to get Arc started. GRASS doesn't work this way. You need to know something about your data and make a choice about what kind of projection you will be working with (even an arbitrary xy representation) before you can even start GRASS. That is, you must make a choice of which "location" you will work with (a location representing a body of geospatial data in a particular projection—including geographic and xy) before you can start GRASS. GRASS has powerful tools for creating a location fairly easily. But I usually advise people to download the demo data so that they have a pre-made location to work with for exploring GRASS.
Both Arc and GRASS have very similar capabilities. I think it is easier to do vector things in Arc and easier to do raster things in GRASS. Arc has somewhat better cartographic capabilities, but GRASS is getting much better at this. Overall, GRASS functions are more accessible than those of ArcGIS. All are within 2 menu levels, and none are hidden inside a separate toolbox. Also GRASS algorithms are all MUCH more accessible than are those of ArcGIS. It is difficult to know what is going on beneath the proprietary GIS functions in Arc, but GRASS not only exposes the algorithms in its open code base, but also provides references to nearly all algorithms in its excellent on-line help.
Arc has a control window (i.e., for layers) attached to every display window. GRASS has a single control window (that includes layer management as well as command console if you prefer it over a GUI approach) for all of its displays. I like the GRASS approach better (naturally) but a lot of people like the Arc approach. I guess it's a matter of opinion and your personal work flows.
One thing that I can say is that when I work with people who are familiar with Arc, I often can solve complex problems in geospatial data analysis more readily with GRASS than they can with Arc. It certainly works very well for my research and teaching needs.
Finally, GRASS runs on Linux, Unix, Mac, and Windows; Arc runs on Windows only.
I hope this is helpful
Michael
On Mar 25, 2012, at 6:59 AM, <
[hidden email]> wrote:
> Date: Sun, 25 Mar 2012 04:34:49 -0700 (PDT)
> From: DOUGLAS NYOLEI <
[hidden email]>
> Subject: [GRASS-user] New GRASS user
> To: "
[hidden email]" <
[hidden email]>
> Message-ID:
> <
[hidden email]>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear all,
>
> My Name is Douglas and I am a new GRASS GIS user. I have been a very active user of ESRI products. Therefore the GIS field is not at all new to me. I have recently been attracted to GRASS GIS because of its strength on Remote sensing with tools that are of great interest to me having been built within GIPE.
>
> I have recently installed GRASS GIS 7.0 in my laptop and over the past week I have been trying to understand how it works. I would therefore greatly appreciate words of advice from other users on getting started with it especially through links to tutorials and manuals. For now my interest is mainly Evapotranspiration estimation from Landsat Images.
> I look forward to hearing from you and becoming a more active Grass user.
>
> Kind regards
>
> ?Douglas
_____________________
C. Michael Barton
Visiting Scientist, Integrated Science Program
National Center for Atmospheric Research &
University Consortium for Atmospheric Research
303-497-2889 (voice)
Director, Center for Social Dynamics & Complexity
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University
www:
http://www.public.asu.edu/~cmbarton,
http://csdc.asu.edu_______________________________________________
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