Newsgroups: info.grass.user
Path: zorro.cecer.army.mil!shapiro
From: shapiro@zorro.cecer.army.mil (Michael Shapiro)
Subject: Re: rectification
Message-ID: <C3I83F.9rD@news.cecer.army.mil>
Sender: news@news.cecer.army.mil (Net.Noise owner)
Organization: US Army Corps of Engineers Construction Engineering Research Labs
References: <93Mar4.135222ast.68@ug.cs.dal.ca>
Date: Sun, 7 Mar 1993 05:47:39 GMT
Lines: 22
In <93Mar4.135222ast.68@ug.cs.dal.ca> brian@ug.cs.dal.ca (Brian Kierstead) writes:
Affine transformation:
x' = ax + by +c
y' = Ax + Bt +C
The a,b,c,A,B,C are determined by least squares regresion based on the
control points entered. This transformation applies scaling, translation
and rotation. It is NOT a general prupose rubber-sheeting, nor is it
ortho-photo rectification using a DEM, not second order polynomial, etc.
It will really only works well if (1) you have geometrically correct images
and (2) the terrain or camera distortion effects can be ignored.
This may not be an appropriate question, it's more math, but how does
i.rectify work? I realize it's a matrix transformation but what is the theory
behind this?
-brian
--
Michael Shapiro U.S. Army CERL
Environmental Division