[postgis-users] Rasters

rb rburghol at chesapeakebay.net
Fri Sep 30 06:49:09 PDT 2005


Paul/others,
Sounds to me that answering the "atomic unit" question is first and
foremost in planning some raster implementation. In my mind I saw it as
a tile type of scenario, whereby the actual data was held outside the
database, one row per tile. I mentioned briefly that the data for these
tiles was essentially an array in postgresql, and in fact, for small
tiles, the array construct could be used as the data unit, similar to
the file format for ASCII rasters, which are themselves simple arrays. 

Regardless of where the atopm data is stored (in DB or filesystem), my
conception is that these rasters would have a polygon geometry column
that described their spatial location and boundaries, but upon the use
of certain raster specific query functions their more detailed nature
would be revealed.

(Taking Gerry) The other issue of course is 3d versus 2d, although I was
fairly certain that postgresql shapes are in fact 3d, having a z
coordinate that is generally assumed to be implicit. The bounding box
geometry schema that I outlined, if my assumtpion of 3d is correct,
would suffice to describe this raster data "slice" in terms of its
spatial relationship to other data entities, while the pixel data that
supplies the raster "texture" (if you will) will provide the data.

It seems that some tool for developing RFP details might be a logical
first step here.

r.b.


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rburghol at chesapeakebay.net




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