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Attn: williamashbless Re: terrestrial tides.	by AndyA	2006-11-19 12:55:59
System setup: I have a dual band GPS system running autonomously (all corrections including WAAS disabled) and logging positions once a second. The antenna is mounted on the roof of our office and should be fairly static. I take the initial altitude measurement and set that as my base line. If between two consecutive positions I see an altitude jump of 1 meter or more then I assume it's caused by a constellation change and reset my base offset in such a way as to indicate no position change. This may sound like a hack at first but typically I see a slow drift of 1 cm every few seconds with a few big jumps that tie up with different SVs moving in and out of view. I then average the altitudes for each minute and store the result. Finally I take my minute by minute results and average them based on a 12 hour 24 minute cycle. Does that all sound reasonable? This plot shows the altitude change over time and the number of points (each a 1 minute average) averaged for each point on the plot. Either we have some huge terrestrial tides around here or other noise is currently swamping the effect. Since the GPS constellation repeat period is just under 12 hours it could prove difficult to distinguish the two different effects. The logging continues...
[ Reply ]
And no, I don't know why I called a png file .jpg (n/t)	by AndyA	2006-07-26 15:04:43
Yyyyeah, those are a little large. :D	by williamashbless	2006-07-26 16:36:17
I just ran through the calculations from scratch	by AndyA	2006-07-26 16:57:52
I thought GPS was lousy at altitude.	by tallastro	2006-11-19 12:55:59
Actually, multiple SVs in a single direction is...	by williamashbless	2006-07-26 20:24:12
That's not what I was taught. Granted, this was a	by tallastro	2006-07-26 20:56:14

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