Compression Techniques and GIS Systems

GRASS GRASS user
1

Thought grasshoppers might not want to miss this one!

In article 10112@netnews.whoi.edu, gie@charon.er.usgs.gov (Gerald I. Evenden)
writes:

Newsgroups: comp.infosystems.gis
>From: sidell@swine.cs.uiuc.edu (Jeff Sidell)
Subject: Compression Techniques and GIS Systems
Date: Sat, 6 Feb 1993 17:18:12 GMT

I would like to know what, if any, data compression techniques are
being used in GIS systems. Specifically, I'm interested in whether
or not any systems represent geographic data as point sets, and
whether or not they compress the data. Please post or e-mail replies.

Jeff Sidell
--
______________________________________________________________________
Jeffrey P. Sidell | "Computers are useless. |
Database Group | All the can do is give |
Department of Computer Science | you answers." |
University of Illinois at Urbana-Champaign | - Pablo Picasso |
----------------------------------------------------------------------

From what I have seen (mostly governmental data types): NONE!

The reason I use an emphatic answer is that I personally believe that
far too little concern has been given to the use of even common techniques
to minimize the size of the physical storage required for gis information.

Too often I have been able to achieve 10-1 compression of the
information with the most primative of techiques. And still make the
data machine independent and transportable. The downside is that
a special procedure must be used to reconstitude the data, but this
is normally fast and, given the slow access of CD-ROMs, can probably
keep up with the input data rate. It possible that compressed data
may actually be more rapidly retrieved from a CD-ROM than raw
information.

For example, the usable information on the USGS 1:2,000,000 vector
map of the USGS requires only ~15Mb versus the ~300Mb on the CD-ROM.
Of course this is misleading, because the distribution contains
triple redunancy and a lot of non-essential fluff.

I have the feeling that most people who are now creating CD-ROMs
have the attitude of "Gee! 600Mb! All I have to do is just dump my
data to the the ROM. I wonder how many discs the TIGER data would
taken if SOME thought had been given to data compression.

There is so much gis information that we are going to be buried up
to our eyeballs if attention to data compression is not forthcoming!

__________________________________________________________________
        Dr Simon Cox
   __ L
      ,~' L_|\ Department of Earth Sciences
   ,-' \ Monash University
   ( \ Clayton Vic 3168 Australia
   \ ___ /
    L,~' "\_x/ Phone +61 3 565 5762
        u Fax +61 3 565 5062
        simon@cerberus.earth.monash.edu.au
__________________________________________________________________

----
__________________________________________________________________
        Dr Simon Cox
         __ L
      ,~' L_|\ Department of Earth Sciences
   ,-' \ Monash University
   ( \ Clayton Vic 3168 Australia
   \ ___ /
    L,~' "\_x/ Phone +61 3 565 5762
              u Fax +61 3 565 5062
        simon@cerberus.earth.monash.edu.au
__________________________________________________________________