grass

[Ken Sibley]

> 
> 	I am a research assistant at the University of Houston Clear Lake.
> I am currently working on a project that involves GRASS. I need to know
> the following question regarding GRASS. If this is not possible to answer
> please be kind enough to refer me to someone who can answer the question
> below.
> QUESTION: 1) What is the data structure used inthe GRASS data file. In
> other words how is the data stored
> 2) What compression technique is used to compress the data files in GRASS.
> 
> Thanking You
> Shameek
> 
This is a very simplistic answer, but will hopefully get you started.
Raster, site and vector files are handled differently in GRASS.
Raster files are either compressed or uncompressed.  Uncompressed
raster files are just plain ascii values stored in a row by column 
method.  I think compressed raster files are stored using a
RLE (run length encoded) method.  There are library routines in grass
to read both as well as to compress/uncompress as needed.
I do not know about the vector files.  Sites files are just
ascii tables using the correct column delimiters.

Ken Sibley
USDA-SCS		"Hell, if you understand everything I say,
ksibley at ncg.scs.ag.gov   you'd be me!"  - Miles Davis


----- End Included Message -----

> From grass-lists-owner%max.cecer.army.mil at munnari.oz.au Wed Jun  8 07:59:17 1994
> Date: Tue, 7 Jun 94 15:40:34 CDT
> From: ksibley at ncg.scs.ag.gov (Ken Sibley)
> Sender: grass-lists-owner at max.cecer.army.mil
> Reply-To: grassp-list at max.cecer.army.mil
> To: grassp-list at max.cecer.army.mil
> Subject: Re: grass
> Cc: grassp-list at max.cecer.army.mil
> Content-Length: 1211
> 
> 
> > 
> > 	I am a research assistant at the University of Houston Clear Lake.
> > I am currently working on a project that involves GRASS. I need to know
> > the following question regarding GRASS. If this is not possible to answer
> > please be kind enough to refer me to someone who can answer the question
> > below.
> > QUESTION: 1) What is the data structure used inthe GRASS data file. In
> > other words how is the data stored
> > 2) What compression technique is used to compress the data files in GRASS.
> > 
> > Thanking You
> > Shameek
> > 
> This is a very simplistic answer, but will hopefully get you started.
> Raster, site and vector files are handled differently in GRASS.

> Raster files are either compressed or uncompressed.  Uncompressed
>!! raster files are just plain ascii values stored in a row by column 
                      =======================
> method.  I think compressed raster files are stored using a
> RLE (run length encoded) method.  There are library routines in grass
> to read both as well as to compress/uncompress as needed.
> I do not know about the vector files.  Sites files are just
> ascii tables using the correct column delimiters.
> 
> Ken Sibley
> USDA-SCS		"Hell, if you understand everything I say,
> ksibley at ncg.scs.ag.gov   you'd be me!"  - Miles Davis
> 
Uncompressed raster files are BINARY not ASCII ! Values in raster files
may be byte,integer*2 or integer*4.

        Rod Paterson
        Aberfoyle Resources Ltd
        Phone: 61-3-8822226
        Fax:   61-3-8131086
        Email: rgp at aberfoyle.oz.au