[time-nuts] How can I measure GPS Antenna quality?

Mark Sims holrum at hotmail.com
Wed Nov 23 00:37:47 EST 2016

The interpolation does not spread the data to where sats have not appeared...  what it effectively does is intelligently make the dots bigger...  but only along the azimuth "axis".   

For each elevation angle, it starts at azimuth 0 degrees and searches forward until it sees a point with signal.  It then searches forward up to 22.5 degrees looking for the next azimuth point at that elevation that has seen signals.  If it finds one, it colors in the arc between those two points (providing that the arc lies inside the clipping boundaries which prevents spreading the interpolation to areas that have not seen signals).  As more sky data is collected over time  the space between adjacent azimuth points at a given elevation narrows and less "filling in" occurs.

Attached are two gifs,  one of the raw data from 24 hours and the other the interpolated data.  Note that areas near the horizon and to the north where no sats are seen are not colored.  The interpolation gives an excellent representation of your sky coverage.


It is unclear to me that interpolating the data 
to areas of the sky where satellites never appear has any utility.

I suppose it makes trends somewhat easier to spot -- but that could also 
be done just by making the dots on the raw chart a bit larger, without 
suggesting a continuity of reception-space that doesn't exist.
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