Unified Fourier Reconstruction (gridding)

This is some earlier work of mine. I was working on an algorithm to impelment Band-limited interpolation from unevenly spaced sampled data after Mehrdad Soumekh. It is also known as “gridding” in SAR and CAT communities (see The gridding method for image reconstruction by Fourier transformation Schomberg, H. and Timmer, J., for example).

The best way to delve into the secrets of UFR is probably to have a look at some code. This file accompanied the book “Fourier Array Imaging” by M. Soumekh. The book is out of print, but you might find it in a good technical university library.

Unfortunately, one cannot place m-files here. So I’ll just drop the code in the text. The convention will be that text in bold italics will mark separate Matlab scripts or functions. Normal text is the Matlab code itself. They should all run without a hitch – you’ll just need to fix some wrapped lines, I suspect. Also, the indentations disappeared, but I don’t have time to fix that now. If there are some other problems, please let me know.

Notes on SAR Interferometry; Ionospheric influence

My student recently defended her thesis on ionospheric influence on SAR interferometry (InSAR). The problem was a possibility of significant ionospheric influence on space-borne InSAR at low frequencies (P-band) used in forest monitoring, for example. Here’s a few musings on the modeling of the problem. Obviously, this post will go to the scientific section…

Visualize, Visualize

As a researcher in multi-dimensional data processing, one inevitably encounters the problem of data visualization. It is no problem to visualize 1D or 2D data nowadays… After some searching, I realized it isn’t too big a deal to visualize your 3d data either! Here’s how.

I have abandoned Matlab some time ago, to embrace free software such as Scilab, for scientific calculations. Compared to Matlab, though, Scilab has a little more problems with visualization. Some early endeavors of mine included fighting with Scilab’s 2D plotting functions and using the excellent ENRICO toolbox for 3d data. But now, I’ve discovered VTK…

Playing With Shifts

This post is related to a very specific problem that I was solving. (Which one isn’t…?) It will hopefully find its use in low resolution SAR and sonar systems. I hope to publish it soon and this is the first try. I expect some trouble with mathematics. So, if you are good at Math, and you are reading this, let me know what you think.

Mean Removal Experiments

This post is a follow up of the text posted yesterday (I’m afraid this will often be the case ). It is related to radar, sonar and multi-channel signal processing, singular value decomposition, matched filtering, and more specifically to something that’s called clutter rejection.

Some Experiments with Eigenanalysis of Data Matrices

This post gives some examples of the use of singular value decomposition (SVD) in some data separation problems. Could be useful in radar, sonar, computer tomorgaphy, etc…

Let’s start with having a look where to find some info on this… The problem at hand is also called the principal components analysis (PCA). So, the book by J V Stone is an excellent start. Lately, I have found the following reference. A lot of ideas (and inspiring Matlab code) came from the HOSA (higher-order spectral analysis) Matlab package and its accompanying manual. There will be probably much more (possibly better) references to study. If you know any good ones, please let me know.

The examples are accompanied with a Scilab code. Scilab is a free equivalent of Matlab. I would encourage to try the code, simply by pasting it into a workspace window. You could either use Matlab (then you need to make some changes) or you can try Scilab (it doesn’t take too much effort and disk space to install it).

Hello world!

All right now, so this is bloggin’! Wow… Well, this blog is primarily meant to be some kind of a platform where I’m going to try to formulate my ideas before I shape them into some more academic form. The reason why I choose blog is obvious: researches are usually requested to have log book. So, I hope this could be it. It seems to give a perfect opportunity to simply put things down as they pop up in my head without any need to be accurate in mathematics or writing style — on contrary, I hope that perhaps I might even get some suggestions from the outside world… let’s see

I was encouraged by blogs like this one and this one. Of course, a question of “scientific priority” and copyright issues came to my mind, so I did my search: this is a very interesting blog in this regard and a very nice one, too. )