your mail

[Malcolm Williamson]

Hi, Casey.
You're partly on track. See the notes below.

On Mon, 14 Aug 1995, Casey Claiborne wrote:

> Hello,
>         I was trying to get some clarification on the database structures of 
> Grass :-)
> 
> I know that they are set as follows:
> 
> GISDBASE - the top level of the database

Correct. This is simply a directory path on your system; it could 
be /home/casey, or /data/grass, for example.

>         LOCATIONS - independent databases within GISDBASE 

LOCATIONS are based upon common geographic location, and, 
very importantly, common map projection or coordinate 
system. Technically, a LOCATION is nothing more than a subdirectory 
directly under GISDBASE, containing required and optional files and 
subdirectories.

>                 MAPSET - under locations, provides more detail. 

MAPSETS are subdirectories under LOCATIONS, owned by individual users of 
GRASS. All work by users ends up in MAPSETS that are _owned_ (not just 
write-permitted) by them. MAPSETS must all be within the geographic 
region and the map projection defined by the LOCATION.

> 
> As an example, does this sound OK
> 
> (Country) GISDBASE - United States

This must be a valid directory name - spaces are not permitted.

> (State)LOCATIONS - Texas, California, New York, etc.

Again, these are directory names, and must follow appropriate UNIX naming 
conventions. Whether or not you could use a single state for each 
LOCATION depends upon your map projection. For state plane, this would 
not work, as many states have more than one zone. For example, Arkansas 
would require two distinct LOCATIONS in state plane, as there are two 
zones. UTM has similar problems, depending on the state. If you have not 
already done so, you need to learn about datums, ellipsoids & geoids, and 
projections - this is true for any GIS system.

> (City) MAPSET - San Francisco, Dallas, New York, Houston, etc.

No. MAPSETS are typically named by user - joe,casey,kathy,etc. You can 
have more than one mapset owned by a user, but they have to have 
different names.

> 
> Or should it be organized differently?
> 
> Would appreciate some help in this matter.
> 
> Thanks
> 
> Casey
> 
> 
> One must note the importance of setting reasonable and achievable goals for
>                     "If you aim for nothing, you'll hit it every time" 
>                                -Theodore Roosevelt
> 
> 
Hope this helps somewhat!
--
Malcolm D. Williamson - GIS Specialist           E-mail: malcolm at cast.uark.edu
Center for Advanced Spatial Technologies      Telephone: (501) 575-6159
Ozark Rm. 12                                        Fax: (501) 575-5218 
University of Arkansas              
Fayetteville, AR 72701