[time-nuts] Reproducibility of position data from multiple surveys of HP 58503A GPS receiver

[Christopher Hoover]

My 58503A was showing an alarm when I came into the shack this morning.
(I forgot to jot down the text on the display.)  I cleared the alarm
(Shift-Alt) and it otherwise seems 100% happy.

-ch
73 de AI6KG

On Sun, Jan 1, 2017 at 7:02 AM, Dr. David Kirkby - Kirkby Microwave Ltd <
drkirkby at kirkbymicrowave.co.uk> wrote:

> 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 2 hour.
> 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
>
> http://www.kirkbymicrowave.co.uk/HP-58503A/gps.log
>
> 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.
>
> http://www.kirkbymicrowave.co.uk/HP-58503A/gps-height.pdf
>
> 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 moan then!
>
> 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.
> http://www.kirkbymicrowave.co.uk/
> Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
>
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