[postgis-users] General Question on Raster within PostGIS

[Angus Carr]

The coordinate transformation parameters are the ones from a world file.

A = x-scale; dimension of a pixel in map units in x direction
B, D = rotation terms
C, F = translation terms; x,y map coordinates of the center of the
upper-left pixel
E = negative of y-scale; dimension of a pixel in map units in y direction

The terms are in ADBECF order. The coordinate transformation equations are:

x1 = Ax + By + C
y1 = Dx + Ey + F

where
x1 = calculated x-coordinate of the pixel on the map
y1 =  calculated y-coordinate of the pixel on the map
x = column number of a pixel in the image
y = row number of a pixel in the image

My reference for this is the ArcView 3.2 help file, but there are others out
there.

Angus Carr.



-----Original Message-----
From: postgis-users-admin at postgis.refractions.net
[mailto:postgis-users-admin at postgis.refractions.net]On Behalf Of Roger
Bedell
Sent: Thursday, May 09, 2002 1:57 PM
Hisaji,

Questions:
1)       I'm not sure what the affine transform is used for?


-----Original Message-----
From: postgis-users-admin at postgis.refractions.net
[mailto:postgis-users-admin at postgis.refractions.net] On Behalf Of Hisaji ONO
Sent: Thursday, May 09, 2002 8:51 AM
To: postgis-users at postgis.refractions.net
Subject: Re: [postgis-users] General Question on Raster within PostGIS

>Hi Everyone,
>
>I'm new to this list, so please excuse this if it has already been
answered.
>
>How are people storing raster images (satellite, aerial photos etc) within
PostGIS?

...
 where "geo_value" is polygons which is extent of images, "urlname" is
URL  of images,  "ox" and "oy" are origin coordinate in pixel, "width"
and "height" are literally images' ones in pixel, "a" - "f" are
parameters of affine tranformation for images deriving from world files