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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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  #11  
Old September 9th 16, 11:14 AM posted to uk.railway,uk.rec.gps
Tony Mountifield[_2_]
external usenet poster
 
Posts: 6
Default GPS receivers and possible OHLE interference

In article ,
NY wrote:
the country because the phone uses so much power winding up the gain on the
mobile phone receiver to listen for incoming calls - oh to be in an area
that has good mobile reception.


Changing the gain on a receiver shouldn't make much difference to consumption.
I always considered that the battery got drained faster in poor signal areas
because the phone winds up its transmit power in order to make itself heard
by the base station. It gets warmer for the same reason.

And it's not just in the countryside. EE is pretty poor in the west half of
Winchester too, and has been since they turned off some of their base stations
after merging Orange and T-Mobile.

Cheers
Tony
--
Tony Mountifield
Work: - http://www.softins.co.uk
Play: - http://tony.mountifield.org
  #12  
Old September 9th 16, 11:30 AM posted to uk.railway,uk.rec.gps
Martin Coffee
external usenet poster
 
Posts: 2
Default GPS receivers and possible OHLE interference

On 09/09/16 12:14, Tony Mountifield wrote:
In article ,
NY wrote:
the country because the phone uses so much power winding up the gain on the
mobile phone receiver to listen for incoming calls - oh to be in an area
that has good mobile reception.


Changing the gain on a receiver shouldn't make much difference to consumption.
I always considered that the battery got drained faster in poor signal areas
because the phone winds up its transmit power in order to make itself heard
by the base station. It gets warmer for the same reason.

And it's not just in the countryside. EE is pretty poor in the west half of
Winchester too, and has been since they turned off some of their base stations
after merging Orange and T-Mobile.


Switching off the wifi can help improve GPS on some services. The on
board wifi can give a false approximate location to "seed" the GPS. As
I recall gWr's wifi placed me in Victoria, London the last time I used
their wifi.
  #13  
Old September 9th 16, 01:01 PM posted to uk.railway,uk.rec.gps
NY
external usenet poster
 
Posts: 10
Default GPS receivers and possible OHLE interference

"Martin Coffee" wrote in message
...
Switching off the wifi can help improve GPS on some services. The on
board wifi can give a false approximate location to "seed" the GPS. As I
recall gWr's wifi placed me in Victoria, London the last time I used their
wifi.


When I first got my Android phone, "Use wireless networks: Locaton
determined by wifi and/or mobile networks" on Settings | Location Services
page was turned on. I got some *very* bizarre results that placed me several
thousand miles away: it alternated between perfectly accurate and being a
long way away.

I googled for the symptom and found that I should turn this option off.
Never had any problems since then.

  #14  
Old September 9th 16, 01:14 PM posted to uk.railway,uk.rec.gps
[email protected]
external usenet poster
 
Posts: 1
Default GPS receivers and possible OHLE interference

On 08.09.16 23:54, Recliner wrote:
BevanPrice wrote:
On 08/09/2016 22:30, 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 line.

This is the track https://s15.postimg.org/d2qin2m3v/GPS.png - the green
arrows show what was actually recorded and I've drawn a red line that
shows where she actually went.


(*) 25 kV AC overhead electrification, for non-railway people in uk.rec.gps



More likely to be reduction of signal when passing under the bridge. You
get the same effect with hand-held GPS units in trains when they are in
cuttings (especially tree-surrounded), or inside tunnels. Except in some
types of train (e.g. Voyagers), these GPS units generally perform O.K.
on either electrified or non-electrified lines.

(Voyagers and some other trains have window coatings that largely block
the GPS signal.)


Yes, for example you get a good GPS signal in older TGVs (including 373s),
but not in new ones, which must have coated windows.

Anybody use a magnetic compass on electrified rail tracks or near an
EMU? You can tell when a train is coming even before it makes itself heard.
  #15  
Old September 9th 16, 01:17 PM posted to uk.railway,uk.rec.gps
Basil Jet
external usenet poster
 
Posts: 1
Default GPS receivers and possible OHLE interference

On 2016\09\09 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.


I saw something similar when my TomTom mistakenly thought for several
minutes that I was 2km north of where I actually was. It tracked my
west-east progress progress correctly and tried to fit it onto the road
network where there weren't many east-west roads.

  #16  
Old September 10th 16, 09:09 AM posted to uk.railway,uk.rec.gps
Roland Perry
external usenet poster
 
Posts: 5
Default GPS receivers and possible OHLE interference

In message
-septe
mber.org, at 08:37:54 on Fri, 9 Sep 2016, Recliner
remarked:
I'm very familiar with the problem of getting GPS reception inside a train
with heat-reflecting windows. I've found that the best thing is to start
recording before you get on the train, while there is still good reception
and plenty of visible satellites, and then the track will continue (maybe
with a bit more jitter) when you get on the train. If I leave it until I'm
on the train before turning on my phone's GPS receiver, it never gets a GPS
fix.


Even if you have a fix with six it more satellites before getting on the
train, you'll periodically lose it during the journey when the train is in
tunnels, deep cuttings and covered stations. The device will then have to
attempt to get a new fix, which will fail if the windows are shielded or
you don't hold it near a window.


Remember also that the GPS receivers in phones vary considerably in
their sensitivity, they aren't nearly as homogenous as the GSM
receivers.
--
Roland Perry
  #17  
Old September 10th 16, 09:15 AM posted to uk.railway,uk.rec.gps
Roland Perry
external usenet poster
 
Posts: 5
Default GPS receivers and possible OHLE interference

In message ,
at 12:13:53 on Fri, 9 Sep 2016, Sam Wilson
remarked:
... 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


That's more of a setting in the Satnav software than the GPS receiver.

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.


I experienced it once on the train from Nottingham to Grantham, using
the now hard to get Microsoft Autoroute and a separate GPS dongle, on my
laptop. It was also perhaps a function of the railway line roughly
following (average about half a km north of) the A52 most of the way.
--
Roland Perry
  #18  
Old September 10th 16, 09:18 AM posted to uk.railway,uk.rec.gps
Roland Perry
external usenet poster
 
Posts: 5
Default GPS receivers and possible OHLE interference

In message , at 11:14:08 on Fri, 9
Sep 2016, Tony Mountifield remarked:
And it's not just in the countryside. EE is pretty poor in the west half of
Winchester too, and has been since they turned off some of their base stations
after merging Orange and T-Mobile.


Yes, where I live used to have good coverage on Virgin (over the top of
EE), but recently they've rationalised base stations and I can only
"see" one rather T-Mobile one (with the added joy that's it's officially
intermittent but the can't be bothered to fix it).

As a result they've lost three lucrative accounts to O2 - having tried
3, which was a rather frying pan into the fire experience.

--
Roland Perry
  #19  
Old September 10th 16, 09:20 AM posted to uk.railway,uk.rec.gps
Roland Perry
external usenet poster
 
Posts: 5
Default GPS receivers and possible OHLE interference

In message , at 12:30:16 on Fri, 9 Sep
2016, Martin Coffee remarked:

Switching off the wifi can help improve GPS on some services. The on
board wifi can give a false approximate location to "seed" the GPS. As
I recall gWr's wifi placed me in Victoria, London the last time I used
their wifi.


My local buses have "free wifi", and if used for geolocation by mapping
software puts me in a village ten miles away which I presume is where
their depot is.
--
Roland Perry
  #20  
Old September 10th 16, 03:14 PM posted to uk.railway,uk.rec.gps
Martin Coffee
external usenet poster
 
Posts: 2
Default GPS receivers and possible OHLE interference

On 10/09/16 10:18, Roland Perry wrote:
In message , at 11:14:08 on Fri, 9
Sep 2016, Tony Mountifield remarked:
And it's not just in the countryside. EE is pretty poor in the west
half of
Winchester too, and has been since they turned off some of their base
stations
after merging Orange and T-Mobile.


Yes, where I live used to have good coverage on Virgin (over the top of
EE), but recently they've rationalised base stations and I can only
"see" one rather T-Mobile one (with the added joy that's it's officially
intermittent but the can't be bothered to fix it).

As a result they've lost three lucrative accounts to O2 - having tried
3, which was a rather frying pan into the fire experience.

They lost a business account from my friends near Chepstow when they
rationalised their masts there. I rather like staying with them as no
one can contact me!
 




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