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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 receiver in phone occasionally gives bizarre coordinates



 
 
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  #1  
Old December 27th 12, 09:34 AM posted to uk.rec.gps
NY
external usenet poster
 
Posts: 10
Default GPS receiver in phone occasionally gives bizarre coordinates

I've just got a Samsung Galaxy SII phone which has a built-in GPS receiver.
It's got both the built-in (Google) Maps application and Viewranger which
I've installed.

When I went out for a walk yesterday (open countryside near a reservoir and
dam, with no tall buildings or deep ravines nearby!) I noticed that the
phone, which had tracked the route perfectly in the car, started alternating
between correct readings and readings that were wrong by about 30 degrees
(!) in latitude, though more or less correct in longitude. It affected both
Viewranger (which was recording a track) and Google Maps (which can't record
a track).

Two other GPS devices (the old Nokia phone and my fiancee's new Google Nexus
tablet) gave perfect results in identical conditions (ie walking alongside
me) so it wasn't due to poor satellite reception conditions.

It's possible I may have been carrying the phone with my hand over the
antenna, or had it in my pocket close to coins and a metal zip, but would
this have accounted for stupid results?

In my experience of an older Nokia phone with GPS, if there are insufficient
satellites visible it just fails to return any value at that time. Sometimes
if I've had my hand over the antenna there has been a random or systematic
error of a hundred metres or so, but I've never seen errors of hundreds or
thousands of miles!

Since then, I've installed an app which shows the DOP and the number of
satellites, so if I see the same symptoms again, I can look at the quality
of the satellite reception.

Today, even inside a cottage with 2-foot thick stone walls, I'm getting HDOP
of about 1.5 and can see 6-8 satellites, which is quite impressive!


So my question is: should a GPS return clearly very wrong coordinates at
times of poor reception, or should it just return no value (a missed data
point)?

  #2  
Old December 27th 12, 01:04 PM posted to uk.rec.gps
Peter[_4_]
external usenet poster
 
Posts: 9
Default GPS receiver in phone occasionally gives bizarre coordinates

On 27/12/2012 10:34, NY wrote:
I've just got a Samsung Galaxy SII phone which has a built-in GPS
receiver. It's got both the built-in (Google) Maps application and
Viewranger which I've installed.

When I went out for a walk yesterday (open countryside near a reservoir
and dam, with no tall buildings or deep ravines nearby!) I noticed that
the phone, which had tracked the route perfectly in the car, started
alternating between correct readings and readings that were wrong by
about 30 degrees (!) in latitude, though more or less correct in
longitude. It affected both Viewranger (which was recording a track) and
Google Maps (which can't record a track).

Two other GPS devices (the old Nokia phone and my fiancee's new Google
Nexus tablet) gave perfect results in identical conditions (ie walking
alongside me) so it wasn't due to poor satellite reception conditions.

It's possible I may have been carrying the phone with my hand over the
antenna, or had it in my pocket close to coins and a metal zip, but
would this have accounted for stupid results?

In my experience of an older Nokia phone with GPS, if there are
insufficient satellites visible it just fails to return any value at
that time. Sometimes if I've had my hand over the antenna there has been
a random or systematic error of a hundred metres or so, but I've never
seen errors of hundreds or thousands of miles!

Since then, I've installed an app which shows the DOP and the number of
satellites, so if I see the same symptoms again, I can look at the
quality of the satellite reception.

Today, even inside a cottage with 2-foot thick stone walls, I'm getting
HDOP of about 1.5 and can see 6-8 satellites, which is quite impressive!


So my question is: should a GPS return clearly very wrong coordinates at
times of poor reception, or should it just return no value (a missed
data point)?


I've had some oddities as well. My HTC Wildfire, while beside the pool
in Corfu Greece was insisting it was in Cisco City, Texas! A Nokia X6 in
my other pocket was giving the right answer. Turning the wifi off in the
HTC resulted in a very slow but correct fix. Fortunately I knew where I was
  #3  
Old December 27th 12, 07:12 PM posted to uk.rec.gps
NY
external usenet poster
 
Posts: 10
Default GPS receiver in phone occasionally gives bizarre coordinates

"Peter" wrote in message ...

On 27/12/2012 10:34, NY wrote:
So my question is: should a GPS return clearly very wrong coordinates at
times of poor reception, or should it just return no value (a missed data
point)?


I've had some oddities as well. My HTC Wildfire, while beside the pool in
Corfu Greece was insisting it was in Cisco City, Texas! A Nokia X6 in my
other pocket was giving the right answer. Turning the wifi off in the HTC
resulted in a very slow but correct fix. Fortunately I knew where I was.


Now I think about it, I think I had the WiFi adaptor turned off when I
experienced the bizarre track - more as a means of saving battery power than
because it might change the GPS abilities.

I found a posting on a forum which recommended turning off a feature in the
Location Services section of Android "Use sensor aiding" - the description
is "Enhance positioning and save power using sensors". I wonder if it means
that it resorts to inertial sensing if it loses GPS, to try to deduce your
approximate location, correcting any systematic errors that this might cause
once it gets another GPS fix.

Since I've turned off "Use sensor aiding" I've not seen any instances of the
phone alternating between the correct location and a stupid location, even
on a walk today where I deliberately kept the phone in my pocket or covered
the sensor with my hand - trying as hard as possible to fool the GPS. And it
followed the route perfectly. I also left it recording a track all last
night: obviously there was a "spider" track due to the random variation in
the detected position over the hours, but it was all confined to a hundred
yards or so - there were no random trips of 1000 miles or more!

  #4  
Old December 28th 12, 03:01 PM posted to uk.rec.gps
R. Mark Clayton
external usenet poster
 
Posts: 119
Default GPS receiver in phone occasionally gives bizarre coordinates


"Anthony R. Gold" wrote in message
...
On Thu, 27 Dec 2012 20:12:10 -0000, "NY" wrote:

I found a posting on a forum which recommended turning off a feature in
the
Location Services section of Android "Use sensor aiding" - the
description
is "Enhance positioning and save power using sensors". I wonder if it
means
that it resorts to inertial sensing if it loses GPS, to try to deduce
your
approximate location, correcting any systematic errors that this might
cause
once it gets another GPS fix.


I believe "Enhanced Positioning" uses the locations of cellular phone
sites,
either in during any absence of satellite signals or as an aid to getting
an
initial approximate location. Maybe some of the cell sites themselves have
configuration errors or else perhaps there are errors in the database of
them used by the mapping software.


No it downloads the current almanac, rather than waiting for it to come
around from the satellites themselves.


  #5  
Old December 28th 12, 03:07 PM posted to uk.rec.gps
R. Mark Clayton
external usenet poster
 
Posts: 119
Default GPS receiver in phone occasionally gives bizarre coordinates


"NY" wrote in message
o.uk...
I've just got a Samsung Galaxy SII phone which has a built-in GPS
receiver. It's got both the built-in (Google) Maps application and
Viewranger which I've installed.

When I went out for a walk yesterday (open countryside near a reservoir
and dam, with no tall buildings or deep ravines nearby!) I noticed that
the phone, which had tracked the route perfectly in the car, started
alternating between correct readings and readings that were wrong by about
30 degrees (!) in latitude, though more or less correct in longitude. It
affected both Viewranger (which was recording a track) and Google Maps
(which can't record a track).

Two other GPS devices (the old Nokia phone and my fiancee's new Google
Nexus tablet) gave perfect results in identical conditions (ie walking
alongside me) so it wasn't due to poor satellite reception conditions.

It's possible I may have been carrying the phone with my hand over the
antenna, or had it in my pocket close to coins and a metal zip, but would
this have accounted for stupid results?

In my experience of an older Nokia phone with GPS, if there are
insufficient satellites visible it just fails to return any value at that
time. Sometimes if I've had my hand over the antenna there has been a
random or systematic error of a hundred metres or so, but I've never seen
errors of hundreds or thousands of miles!

Since then, I've installed an app which shows the DOP and the number of
satellites, so if I see the same symptoms again, I can look at the quality
of the satellite reception.

Today, even inside a cottage with 2-foot thick stone walls, I'm getting
HDOP of about 1.5 and can see 6-8 satellites, which is quite impressive!


So my question is: should a GPS return clearly very wrong coordinates at
times of poor reception, or should it just return no value (a missed data
point)?


Three main possibilities he -

1. Bug in the phone.

2. Only using the clear acquisition signal and this repeats on the earth's
surface unless you have an idea where you are to start with or wait a long
time to deduce and eliminate the 'wrong' answers from which satellites are
actually in view.

3. Phone forgets where it was last used to navigate.


3.5 your cottage may have 600mm thick stone walls, but I doubt the roof is
that thick. Your phone should see enough satellites through that aperture,
although the CEP will be worse than in the open. Blackberry phones have an
app that displays the signal strength of all satellites and graphically
around a globe for those in view.


  #6  
Old December 28th 12, 07:50 PM posted to uk.rec.gps
NY
external usenet poster
 
Posts: 10
Default GPS receiver in phone occasionally gives bizarre coordinates

"Anthony R. Gold" wrote in message
...

On Fri, 28 Dec 2012 16:01:53 -0000, "R. Mark Clayton"
wrote:


"Anthony R. Gold" wrote in message
...
On Thu, 27 Dec 2012 20:12:10 -0000, "NY" wrote:

I found a posting on a forum which recommended turning off a feature in
the
Location Services section of Android "Use sensor aiding" - the
description
is "Enhance positioning and save power using sensors". I wonder if it
means
that it resorts to inertial sensing if it loses GPS, to try to deduce
your
approximate location, correcting any systematic errors that this might
cause
once it gets another GPS fix.


I believe "Enhanced Positioning" uses the locations of cellular phone
sites,
either in during any absence of satellite signals or as an aid to getting
an
initial approximate location. Maybe some of the cell sites themselves
have
configuration errors or else perhaps there are errors in the database of
them used by the mapping software.


No it downloads the current almanac, rather than waiting for it to come
around from the satellites themselves.


http://en.wikipedia.org/wiki/Enhanced_GPS


The Wikipedia article makes it sound like a Good Idea, but it does depend on
you being able to see wifi networks and/or mobile phone networks in the
absence of GPS. As it happens, the place where I got the ridiculous GPS
values was on a walk in the middle of nowhere (near Hannah Hauxwell's house
in Teesdale) where there was almost certainly no wifi/mobile coverage.

I'm sure the problem was that I was covering the GPS aerial, but rather than
giving fewer GPS fixes or ones with minor errors, it somehow returned values
that were hundreds or thousands or miles off-target, interspersed with valid
results. The problem lasted only while I was on foot (with the phone in
either trouser or anorak pocket) and was fine for all the time before and
after the walk when the phone was horizontal on the centre console of my
car.

It's not done it since (with Enhanced GPS turned off) though it does follow
the correct route (by comparison with OS map) less well when it's vertical
in my pocket than when it's horizontal in the car. But those are just missed
points or errors of up to 100 metres. I've not seen any more of the really
gross errors.

  #7  
Old January 2nd 13, 05:37 PM posted to uk.rec.gps
external usenet poster
 
Posts: 1
Default GPS receiver in phone occasionally gives bizarre coordinates

Dana ńćetvrtak, 27. prosinca 2012. 11:34:47 UTC+1, korisnik NY napisao je:
[...]
When I went out for a walk yesterday (open countryside near a reservoir and
dam, with no tall buildings or deep ravines nearby!) I noticed that the
phone, which had tracked the route perfectly in the car, started alternating
between correct readings and readings that were wrong by about 30 degrees
(!) in latitude, though more or less correct in longitude. It affected both
Viewranger (which was recording a track) and Google Maps (which can't record
a track).

[...]

I, too, had similar problems with my last Android. Later I discovered that
part of the problem was that Google caches IDs of wireless networks. And this
"cache" is not upgraded quickly. For example, I moved to a new city (50km
distance) but even 1 year later Google was still thinking my WiFi was on my
old location.

The other thing that resulted in big GPS errors was the "Use sensor aiding"
option. After I turned both options to off (wifi and sensor) the GPS position
was accurate.

Cheers,
tk

--
www.trackprofiler.com -- Online GPS Track Editor
 




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