GPS Pop Quiz

9 years ago
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boardsurfr
boardsurfr
WA
2463 posts
WA, 2463 posts
26 Dec 2016 10:41am
My apologies in advance, but I cannot not do this .. here's a pop quiz:


1. One GPS is GW-52, one is a GW-60 - which is which?
2. Why are the tracks so different?

Peeking at my blog to find the answer is cheating!

Merry Christmas!
Simon100
Simon100
QLD
490 posts
QLD, 490 posts
26 Dec 2016 11:36pm
I was going to say filter , but then I checked the blog
Xbraun54
Xbraun54
74 posts
74 posts
27 Dec 2016 2:24am
For sure something with noise i guess :)
sailquik
sailquik
VIC
6171 posts
VIC, 6171 posts
27 Dec 2016 12:01pm
Is that 5Hz data?
Simon100
Simon100
QLD
490 posts
QLD, 490 posts
27 Dec 2016 11:55pm
you can clearly see your stride is around 75cms ( if a@ 5hz)
boardsurfr
boardsurfr
WA
2463 posts
WA, 2463 posts
28 Dec 2016 2:01am
sailquik said..
Is that 5Hz data?


Yes.
decrepit
decrepit
WA
12885 posts
WA, 12885 posts
28 Dec 2016 6:39pm
Simon100 said..
you can clearly see your stride is around 75cms ( if a@ 5hz)



Well done Simon, in that case watch on wrist is traveling further than Gw52 on body, which means blue is watch red is gw52?
boardsurfr
boardsurfr
WA
2463 posts
WA, 2463 posts
28 Dec 2016 10:18pm
decrepit said..

Simon100 said..
you can clearly see your stride is around 75cms ( if a@ 5hz)




Well done Simon, in that case watch on wrist is traveling further than Gw52 on body, which means blue is watch red is gw52?


We have a winner! Yes, that's it. My first thought also was some kind of filtering thing, but I could see that this happened when I was walking along a sand bar, which made it a bit easier to come to the right conclusion.

I looked a bit at traces and aligned SDOP graphs for 4-unit drives (2 each GW-52 and GW-60), and did not see any obvious difference in filtering or accuracy. There are different sections where one or two units have worse accuracy, and that's usually quite obvious in the doppler speed traces; but the units take turns in "being bad". It may have to do with small difference in GPS reception (this was an "inside the van" test). I plan to do a few more tests with units on top of my van where reception should be completely unobstructed in a few weeks, when we get to warmer and less wooded climates. But so far, so good .
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