[time-nuts] Reproducibility of position data from multiple surveys of HP 58503A GPS receiver
Dr. David Kirkby - Kirkby Microwave Ltd
drkirkby at kirkbymicrowave.co.uk
Sun Jan 1 10:02:19 EST 2017
I put my HP 58503A into an infinite loop where
1) Forced GPS receiver to do a survey (GPS:POS:SURVEY ONCE)
2) Waited until survey was complete (GPS:POS:HOLD? returns 1) This takes about
3) Recorded date (SYST:DATE?), time (SYST:TIME?) and location (GPS:POS?)
For about 4 hours before the leap second, I stopped this, so the clock was right
at the time of the leap second. Then I restarted some time after midnight.
The actual data file is here
which is being updated whenever a survey is complete, and new data collected -
about once every 2 hours.
A plot of the height from the first 19 data points is here.
Unlike hte log, this is not being updated dynamically - I should have used
another machine which has gnuplot on it for that.
Anyway, based on the first 19 data points, the antenna height appears to be
anywhere from 40 to 48.5 m. I'm pretty sure it is not bouncing up and down 8.5
metres! The latitude and longitude move too. I've not converted them into
metres, so I don't know how much they represent.
The antenna is about 3.5 m above ground level, mounted to the side of a garage,
which is higher. I could push it another 2 m or so by mounting it on the garage,
but not without drilling holes in the garage which will not exactly make the XYL
happy, although I guess if I do it when she is not looking, its a bit late to
I was thinking of telling the receiver the location is an "average" of the data
points. Some thought would need to be given to averaging, although I would have
thought in my latitude (51 deg, 39' N), and distance from the meridian (0 deg,
41' E), a simple mean would not be a bad figure. But I stand to be corrected.
Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK.
Registered in England and Wales, company number 08914892.
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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