GPS's aren't just for navigation anymore
Visible light: 0 degrees true north is at the left and right edges.
1.5 GHz GPS: This is a picture of the satellite tracks across the sky. The false color is the signal intensity. The blue is a strong signal the red is a weak signal. The picture is calibrated at 0.5 degrees per pixel in both dimensions. True north is at the lower left and lower right. The top is 90 degree elevation. The bottom is 0 degrees elevation. The occlusion between 40 degrees and 120 degrees with an elevation of 13 degrees is a hill (behind the trees) to the east. The black circle at 0-degrees azimuth 37-degrees elevation is the satellite void around the north pole. (Nota Bene: this picture is calibrated exactly the same as the visible picture and faces in the exact same direction. If one superimposes the two pictures one can clearly see the visible-light features in the satellite picture.)
The goal of this little hack was to take a passive microwave picture of the local skyline using only the gps satellites for illumination. This picture is only a limited exposure. I was hoping that after a few weeks, it should start looking more like a the visible light view of the skyline from the roof. Unfortunately many of the satellites follow the exact same track month after month (without significant procession). The picture just never filled in.
Equipment: Lowe antenna, Garmin G12xl, dgpsip (v1.26-B) recording the data. Olympus D-320L digital camera in "panorama" mode.
The raw unprocessed svtrack.pgm file. Exactly 1 pixel per degree. True north is at pixel 0 and pixel 360. The horizon is at pixel 0. The zenith is at pixel 90.
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