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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | Re: GISList: ArcGIS: gird problems |
| Date: |
08/23/2003 05:40:01 AM |
| From: |
Peter Baumann |
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Julia Reisemann wrote:
> Hi,
>
> does anybody have an idea how to deal with a grid that has an integer
> value but thinks it is a floating point. Is there something like a
> build vat in ArcGis 8?
>
> Hm, grids with personality disorders, what will be next?
>
> Julia
Hi Julia & all,
a technologist's reply: Given the many personalities numbers and grids can
convey :-), a promising approach is to make software intelligent enough to
handle all data types and their arithmetics. In conjunction with a dynamic query
language (yes, I am a database guy) you can teach grids then to behave in
ballroom as well as in the street.
Let me do the small experiment in the rasdaman query language, rasql. Assume
grids over float (or double) numbers.
- "my grid with original data" (returns a float grid in our case)
select grid
from MyGridCollection as grid
- "A 32-bit integer grid from my float grid" (returns an int grid)
select (int) grid
from MyGridCollection as grid
- "A map of the rounding error" (the result is a grid where each pixel holds the
deviation)
select grid - (int) grid
from MyGridCollection as grid
- "Was there any rounding error at all?" (The result is one single boolean
value)
select some_cells( grid - (int) grid != 0 )
from MyGridCollection as grid
Of course a regular user would not be bothered with such syntax, that is
normally hidden in the client code. On the other hand, based on a query language
someone with just intermediate familiarity can handle surprise attacks like
Julia's situation in a few minutes.
So, Julia, I'd argue for tools that respect individuality - if you consider
complex numbers (like for spectral imagery), then you even get split
personalities... :-)
Regards,
Peter
--
Dr. Peter Baumann, Executive Director
rasdaman GmbH
WWW: http://www.rasdaman.com/
Email: mailto:baumann@rasdaman.com
Dialup: voice +49-89-67000146, fax +49-89-67000147, mobile +49-173-5837882
"A brilliant idea is a job halfdone."
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