[GRASS5] [bug #1065] (grass) GRASS and IDRISI

this bug's URL: http://intevation.de/rt/webrt?serial_num=1065
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On Wed, Mar 27, 2002 at 05:49:34PM -0700, David A Hastings wrote:
> I hope to set up the database so that source (e.g. PERMANENT) data will
> be readable on both GRASS and Idrisi. GRASS and Idrisi 8-bit
> uncompressed cell files are identical, one can use links to headers, so
> that source data are interoperable on both systems. I have been doing
> this since 1995. If GRASS let one specify an actual 2-byte integer, and
> specify the byte ordering (say as enhancements to CELLHD files), as is
> possible in programs such as Photoshop, the interoperability would be
> better. And Idrisi has had floating point cell files since its
> inception - though I won't know about compatibility issues with GRASS 5
> for another few weeks. Finally, if GRASS could let the user force files
> to remain uncompressed (again, a field in the CELLHD file),
> interoperability would be helped at the cost of (now cheap) disk space.

If you don't mind, I'll send above to the developers list. Maybe we can do
something.

I'd love to see you make a suggestion. I would do it myself, but I'm
overwhelmed with the move right now. It has been a BIG pain to me that the
history of the Open GRASS Foundation (which became the Open GIS Consortium
when CERL stopped funding OGF for doing things that were inappropriate in
CERL's eyes) causes the Open GIS Consortium to ignore the best starting
platform for open GIS (e.g. GRASS). Nevertheless, GRASS and Idrisi have
existing "de-facto" interoperability at the file level, and are a great
conceptual model for enhancing such interoperability if they could cooperate
on "just a couple of small detials." The complementarity of GRASS and Idrisi
(and perhaps ERDAS, but this might be less likely), and the research aspect
of both GRASS and Idrisi, should be a great motivation to modestly pursue
such interoperability.

> Regards to all,
> David Hastings

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From neteler@itc.it Mon May 27 13:08:43 2002

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-------------------------------------------- Managed by Request Tracker

On Mon, May 27, 2002 at 01:08:44PM +0200, Request Tracker wrote:

this bug's URL: http://intevation.de/rt/webrt?serial_num=1065
-------------------------------------------------------------------------

> On Wed, Mar 27, 2002 at 05:49:34PM -0700, David A Hastings wrote:
> > I hope to set up the database so that source (e.g. PERMANENT) data will
> > be readable on both GRASS and Idrisi. GRASS and Idrisi 8-bit
> > uncompressed cell files are identical, one can use links to headers, so
> > that source data are interoperable on both systems. I have been doing
> > this since 1995. If GRASS let one specify an actual 2-byte integer, and
> > specify the byte ordering (say as enhancements to CELLHD files), as is
> > possible in programs such as Photoshop, the interoperability would be
> > better. And Idrisi has had floating point cell files since its
> > inception - though I won't know about compatibility issues with GRASS 5
> > for another few weeks. Finally, if GRASS could let the user force files

I suspect GRASS and Idrisi FP formats are significantly different. For
FP rasters, GRASS actually stores the data in a different file and has
an additional header file. Whether float, or double size, each file has
an index of row offsets (int) followed by the data. The data itself is XDR
encoded, and each row may be compressed via zlib. The first byte of
each row flags whether the row data is compressed ('0' - no, '1' - yes).

GRASS5 also has a NULL data file to differentiate 0 from NULL. This is
used with all raster types.

--
Eric G. Miller <egm2@jps.net>