brainwagon "There is much pleasure in useless knowledge." — Bertrand Russell

12Aug/091

Volume Rendering: Going boldly where all have gone before…

Image from CT data downloaded from http://graphics.stanford.edu/data/voldata/

Image from CT data downloaded from http://graphics.stanford.edu/data/voldata/

Okay, this is a bit gruesome, but I've been dusting off some old papers that I never really understood on Fourier Volume Rendering, and testing my understanding by writing some simple code that takes in a volume dataset and uses the fast Fourier transform to convert it into simulated X-ray pictures. The data set that this picture was generated from was downloaded from this webpage at Stanford, and consists of CT scan data of a cadaver. The basic code works! Given a bit more work, I should be able to do arbitrary orthographic views.

The math for all this is described quite admirably by Tom Malzbender's paper Fourier Volume Rendering.

Addendum: Here is the raw data slices:


httpv://www.youtube.com/watch?v=UrwnuEtNUKc

Addendum2: Here is a link to some more interesting volume datasets.

Addendum3: Here's my attempt at rotation. It doesn't really work right yet. I think I understand why.


12Aug/092

WSPR signals heard from E51EME

I still check my WSPR station logs each morning when I wake up. This morning I spotted the callsign E51EME, coming from grid square BG08. I've come to realize that many of these spots which include only a four element grid designator are spurious bad decodes, and I didn't recognize the prefix (I'm not much of a DX-er). But still, it decoded multiple times:

Timestamp Call MHz SNR Drift Grid Pwr Reporter RGrid km az
 2009-08-12 12:16   E51EME   10.140137   -22   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 11:44   E51EME   10.140136   -20   -1   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 11:32   E51EME   10.140137   -18   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 11:24   E51EME   10.140136   -17   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 11:14   E51EME   10.140137   -15   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 11:06   E51EME   10.140135   -12   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 10:56   E51EME   10.140137   -12   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 10:44   E51EME   10.140135   -10   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 10:32   E51EME   10.140137   -11   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 10:12   E51EME   10.140137   -11   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 10:04   E51EME   10.140136   -14   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 09:56   E51EME   10.140137   -17   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 09:44   E51EME   10.140136   -18   -1   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 09:34   E51EME   10.140137   -18   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 09:24   E51EME   10.140136   -20   -1   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 09:16   E51EME   10.140137   -19   0   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 09:04   E51EME   10.140136   -19   -1   BG08   5   K6HX   CM87ux   7649   30 
 2009-08-12 08:52   E51EME   10.140136   -19   0   BG08   5   K6HX   CM87ux   7649   30 

A quick trip to QRZ.com verified that this was indeed a real call, Bob Sutton from Raratonga, in the Cook Islands. Very cool.

E51EME in Raratonga, the Cook Islands

E51EME in Raratonga, the Cook Islands

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