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uk.rec.gps (UK Sat Nav) (uk.rec.gps) for the discussion of all aspects of the UK use of Global Positioning Systems and any other satellite positioning/navigation systems which may be developed. Also any improvements, or extensions to the above and radio navigation systems.

GPS receivers and possible OHLE interference

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Old September 10th 16, 05:43 PM posted to uk.railway,uk.rec.gps
Peter Crosland
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Posts: 17
Default GPS receivers and possible OHLE interference

On 09/09/2016 12:13, Sam Wilson wrote:
In article ,
Peter Crosland wrote:

... The better [GPSs] have accelerometers built in that keep track during
signal interruptions. Others also use them to assume that you will
continue on the road you are on. I have never seen such weird results as
shown in the map you listed.

Have you ever seen a GPS receiver with the "I must be on a road" setting
trying to work out where it is when it's on a train? I've only seen it
once a long time ago but it was quite entertaining.

Yes! More modern algorithms can usually distinguish between road and rail.

Peter Crosland

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Old September 10th 16, 07:31 PM posted to uk.railway,uk.rec.gps
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Posts: 1
Default GPS receivers and possible OHLE interference

NY wrote:
We've just got a dashboard camera for the car, and it also has a GPS
receiver. I was looking at the tracks of my wife's journey to work. At one
point she passes under a long bridge beneath many OHLE-electrified (*)
railway tracks close to a station. The GPS track seems to go haywire,
showing her going roughly opposite to the real direction, and this begins
just *before* she goes under the tracks and therefore while she still
theoretically has GPS reception.

Intriguingly, the "dilution of precision" figures (a measure of how much
error there may be in each reading) does not get worse when she approaches
the bridge and the tracks, even though as she starts to turn north, the GPS
track shows her turning south.

Does the radiation from OHLE lines (presumably 50 Hz with lots of harmonics
and noise due to arcing) corrupt GPS signals in such a way as to still show
a reliable GPS signal (low DOP) but with lat-long coordinates varying in the
wrong direction? I'd have expected (if anything) a loss of signal (no GPS
fix) or else points that were distributed at random causing a very wiggly

Many years ago when I lived in Leeds I used to run along the canal towpath
from the city out in to the west. After a couple of km you pass a large
electricity distribution place (where I guess the UHV lines from the pylons
get stepped down to mere HV - it's a big old load of pylons, transformers
and cables anyway.) Running past here the GPS tracks from my mobile phone
would always go completely haywire (I think I achieved a top speed of
100mph according to one such track - eat your heart out, Usain Bolt...)


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