Path: news.mathworks.com!not-for-mail
From: "Matthew Whitaker" <mattlwhitaker@REMOVEgmail.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: image matching
Date: Tue, 21 Aug 2007 21:25:36 +0000 (UTC)
Organization: Radiological Imaging Technology Inc
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"Mark Verzeilberg" <nlda@mathwork.com> wrote in message 
<faepce$o6h$1@fred.mathworks.com>...
> for our project we want to know if it is possible to find 
a
> image in another image and find the position of our Blimp.
> 
> We have a Blimp (kind of a zeppelin) in an old gymanium
> flying around taking pictures of the ground to find an
> object. We have the idea that we can make some kind of
> pattern on the ground so that the blimp can make pictures 
of
> the ground and that they can be matched with a computer 
made
> map with the same pattern as on the ground. This way we 
want
> to determine the position of the blimp. Is this possible
> with MatLab and can we get an update rate of at least 1
> position per second.
> 
> For some more information please ask. The idea is inspired
> on DSMAC (Terrain Referenced Navigation).

Wow,
There are a lot of varaiables here. 
1) What resolution would the floor map be at and what would 
be the overall dimensions in pixels of the floor map.
2) What height would the blimp be at, what would be the 
size of it's field of view and what would the resolution of 
the blimp camera be.
3) What is the size of the target object. Is it two 
dimensional or 3?
4) Are the blimp images fairly stable or is there a lot of 
pitch and yaw effects?


I suppose the first thing to look at would be pattern 
correlation where you would take the image from the Blimp 
camera and correlate it to the known map.  From Gonzalez, 
Woods and Eddins - Digital Image Processing using Matlab 
they have a small function on page 491 that does this
[M,N] = size(f); %where f would be the map
f = fft2(f);
w = conj(fft2(w,M,N); %where w would be the blimp image
g = real(ifft2(w.*f)); 
[I,J] = find(g == max(g(:))); %coordinates of best match

Good Luck!