Bluetooth GPS and Android

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Stewart Robert Hinsley

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Jan 25, 2020, 5:05:20 PM1/25/20
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My GPS is showing signs of age - it still works, but two of the controls
are damaged - so I'm looking into a replacement.

I have a GPS enabled tablet, but the GPS resolution on this isn't all
that good, so just using the tablet isn't an ideal solution.

Does anyone have experience of using the bluetooth enabled GPSs which
delegate the user interface to a host device such as a phone or tablet?

--
SRH

David

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Feb 11, 2020, 10:04:05 AM2/11/20
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No, but I would be interested.

Not much help, I know.

Cheers



Dave R


--
AMD FX-6300 in GA-990X-Gaming SLI-CF running Windows 7 Pro x64

Stewart Robert Hinsley

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Feb 13, 2020, 6:55:07 AM2/13/20
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On 11/02/2020 15:04, David wrote:
> On Sat, 25 Jan 2020 22:05:14 +0000, Stewart Robert Hinsley wrote:
>
>> My GPS is showing signs of age - it still works, but two of the controls
>> are damaged - so I'm looking into a replacement.
>>
>> I have a GPS enabled tablet, but the GPS resolution on this isn't all
>> that good, so just using the tablet isn't an ideal solution.
>>
>> Does anyone have experience of using the bluetooth enabled GPSs which
>> delegate the user interface to a host device such as a phone or tablet?
>
> No, but I would be interested.
>
> Not much help, I know.
>

I've grasped the nettle and ordered a Garmin Glo 2. Reviews say this has
1-2.5m resolution. I've been getting 3-5m from an Etrex, and 8-12m from
my tablet.

It's said to have a 12 hour battery life, which is less than the 18
hours I'm getting from an Etrex. 12 hours is short enough that I'd worry
about running out on a long day, but since I need a powerbank to keep
the tablet going (if I'm using the OS maps app) that's not a killer issue.

Using the GPS on the tablet shortens battery life appreciably. What I
don't know is what the impact of all the bluetooth traffic will be on
battery life. The other issue to getting software to work with it - as I
understand Garmin don't provide any.

--
SRH

Stewart Robert Hinsley

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Feb 18, 2020, 8:39:47 AM2/18/20
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* The manual that comes with it doesn't provide any instructions as to
how to persuade an Android device to pick up the output from this.
Fortunately I has previously found the FAQ on Garmin's web site that
explained how to do this.

* It's achieved 1-2m reported accuracy, which is better than what I've
been getting from the Etrex, or the tablet. (The Etrex was good enough
for my purposes; the tablet wasn't really.) I'll start another composite
GPX file, and see how repeatable routes are.

* It looks like it reduces tablet battery life to about 3.5 hours,
compared to over 10 if there was no GPS. (With the native GPS I was
getting 5 or 6 hours, and needed a powerbank for a day's usage - if I
didn't use the tablet GPS I could get 10 or 12 hours.) I don't really
need 10 readings per second, and perhaps 1 per second would result in a
lower battery usage.

* It works with OS Maps, and there's a Grid Reference app that lets me
paste the current GR, so I can use it for navigation and geolocation
purposes. (Reports are that some apps insist on using the native GPS.)

--
SRH

Nick Maclaren

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Feb 18, 2020, 9:54:48 AM2/18/20
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In article <r2gpf1$r0m$1...@dont-email.me>,
Stewart Robert Hinsley <{$news$}@meden.demon.co.uk> wrote:
>
>* It's achieved 1-2m reported accuracy, which is better than what I've
>been getting from the Etrex, or the tablet. (The Etrex was good enough
>for my purposes; the tablet wasn't really.) I'll start another composite
>GPX file, and see how repeatable routes are.

What's the vertical accuracy?

Regards,
Nick Maclaren.

Stewart Robert Hinsley

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Feb 18, 2020, 11:58:27 AM2/18/20
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I hadn't looked into that - I'm used to assuming that there's too much
noise in GPS altitude readings for it to be useful to me. I'll take a
note to myself to look at it. (There's also the matter of correction
from ellipsoid to geoid - relative heights could be accurate with
absolute heights inaccurate.)

The other thing I'm currently worrying about is whether a powerbank can
recharge the tablet faster than using Bluetooth GPS drains it (though
Android claims that most of the usage was the screen) - with the current
weather condition I have used it for more than a couple of hours at a time.

--
SRH

Stewart Robert Hinsley

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Mar 1, 2020, 6:27:37 AM3/1/20
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On 18/02/2020 14:54, Nick Maclaren wrote:
Not very good. Yesterday, according to a GPS logging app, I ascended
just shy of 3,000 feet. The actual figure would be more like 700 or 800
feet. The difference is because there's a lots of noise, of substantial
magnitude, in the altitude reading.

What I've read if you want an accurate altitude to use the latitude and
longitude to interrogate a detailed terrain database. But it requires a
lot of detail to handle steep slopes. If you're on the edge of a cliff,
even that doesn't help, since there's the horizontal error to take into
account.

As I said earlier, with the screen on, my tablet battery is exhausted
after about 3.5 hours. But provided the screen isn't permanently on a
powerbank can recharge it faster than it's being used.

The Garmin Glo seems to be slightly more accurate (less noisy) that the
Etrex 20, consistent with a reported accuracy of 1-3m, rather than 3-5m
(and much more accurate that the tablet's native GPS). Track distances
come out slightly shorter than, which is consistent with that. (There
may be a countervailing factor of more points, so corners aren't cut on
the measurement.) It looks as if in both cases the figures overstate the
accuracy - if you repeat a route there can be systematic differences
betwween the track greater than the reported accuracy. Perhaps this is
due to accounting for echoes, which will differ because of satellite
positions.

The Garmin Glo seems to be more effective indoors, which may make it
more useable in a train - the Etrex 20 is more often than not dead on a
train, as is the tablet's native GPS.

The big advantage over the Etrex 20 is that I can capture grid
references directly into my field notes - there's an app which will
paste the GR to the Android clipboard, which I can then paste into my
notes. Handy for biological and geological recording, and other
applications looking for high precision position records.

>
> Regards,
> Nick Maclaren.
>

Nick Maclaren

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Mar 1, 2020, 6:44:33 AM3/1/20
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In article <r3g677$tb2$1...@dont-email.me>,
Stewart Robert Hinsley <{$news$}@meden.demon.co.uk> wrote:
>>
>> What's the vertical accuracy?
>
>Not very good. Yesterday, according to a GPS logging app, I ascended
>just shy of 3,000 feet. The actual figure would be more like 700 or 800
>feet. The difference is because there's a lots of noise, of substantial
>magnitude, in the altitude reading.

Thanks very much :-(

>What I've read if you want an accurate altitude to use the latitude and
>longitude to interrogate a detailed terrain database. But it requires a
>lot of detail to handle steep slopes. If you're on the edge of a cliff,
>even that doesn't help, since there's the horizontal error to take into
>account.

I have heard that you can do it by averaging over several hours, by
logging and analysing, but that's no use to me. My interest was in
(a) trying to identify which 'peak' I was on and (b) following a
specific contour line - both in thick mist, of course. It's clearly
NBG for such uses.

I don't need a fancy database, if I have a map! But I do need some
information that I can map from the device to the map, which is a
bit tedious, as the Garmin doesn't give the position in Ordnance
Survey units.

>As I said earlier, with the screen on, my tablet battery is exhausted
>after about 3.5 hours. But provided the screen isn't permanently on a
>powerbank can recharge it faster than it's being used.

I shall continue to use mine for spot checks only :-)

Out of interest, roughly how long does your power bank last, and
how much does it weigh?


Regards,
Nick Maclaren.

Stewart Robert Hinsley

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Mar 1, 2020, 3:12:05 PM3/1/20
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On 01/03/2020 11:44, Nick Maclaren wrote:
> In article <r3g677$tb2$1...@dont-email.me>,
> Stewart Robert Hinsley <{$news$}@meden.demon.co.uk> wrote:
>>>
>>> What's the vertical accuracy?
>>
>> Not very good. Yesterday, according to a GPS logging app, I ascended
>> just shy of 3,000 feet. The actual figure would be more like 700 or 800
>> feet. The difference is because there's a lots of noise, of substantial
>> magnitude, in the altitude reading.
>
> Thanks very much :-(
>
>> What I've read if you want an accurate altitude to use the latitude and
>> longitude to interrogate a detailed terrain database. But it requires a
>> lot of detail to handle steep slopes. If you're on the edge of a cliff,
>> even that doesn't help, since there's the horizontal error to take into
>> account.
>
> I have heard that you can do it by averaging over several hours, by
> logging and analysing, but that's no use to me. My interest was in
> (a) trying to identify which 'peak' I was on and (b) following a
> specific contour line - both in thick mist, of course. It's clearly
> NBG for such uses.
>
> I don't need a fancy database, if I have a map! But I do need some
> information that I can map from the device to the map, which is a
> bit tedious, as the Garmin doesn't give the position in Ordnance
> Survey units.

The Etrex 20, which is a Garmin product, does have the option to display
the OSGB grid reference. I thought that all the posher Garmin products
came with maps.
>
>> As I said earlier, with the screen on, my tablet battery is exhausted
>> after about 3.5 hours. But provided the screen isn't permanently on a
>> powerbank can recharge it faster than it's being used.
>
> I shall continue to use mine for spot checks only :-)
>
> Out of interest, roughly how long does your power bank last, and
> how much does it weigh?

It weighs in the region of 350-400g. It's a 20,000 mAh powerbank, and
the combination of a fully charged tablet and the powerbank has so far
been sufficient to handle 12 hour days, with a substantial margin left
over - I think that the most I've used was 80% of the powerbank, and 60%
was more usual, and with the tablet battery half-charged at the end of
the day as a result.

I'm using the tablet for botanical recording, and for navigation (the OS
Maps app - I carry paper maps as a back up, but the tablet is more
convenient for everyday usage).
>
>
> Regards,
> Nick Maclaren.
>

Nick Maclaren

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Mar 2, 2020, 4:37:30 AM3/2/20
to
In article <r3h4ug$mc4$1...@dont-email.me>,
Stewart Robert Hinsley <{$news$}@meden.demon.co.uk> wrote:
>
>The Etrex 20, which is a Garmin product, does have the option to display
>the OSGB grid reference. I thought that all the posher Garmin products
>came with maps.

That's what I have, too! I will look further - the documentation was
(as usual) pretty ghastly. The maps I have are the open source ones,
and seemed to show only 50m contour lines.

Thanks for the power bank information. I might get one, but it won't
be enough for me to do the same, as I am talking about up to a week
between (mains) recharging. What it would do is to enable me to be
less miserly with my tablet use.


Regards,
Nick Maclaren.

Stewart Robert Hinsley

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Mar 2, 2020, 1:42:15 PM3/2/20
to
On 02/03/2020 09:37, Nick Maclaren wrote:
> In article <r3h4ug$mc4$1...@dont-email.me>,
> Stewart Robert Hinsley <{$news$}@meden.demon.co.uk> wrote:
>>
>> The Etrex 20, which is a Garmin product, does have the option to display
>> the OSGB grid reference. I thought that all the posher Garmin products
>> came with maps.
>
> That's what I have, too! I will look further - the documentation was
> (as usual) pretty ghastly. The maps I have are the open source ones,
> and seemed to show only 50m contour lines.

It's on the Satellite display, and is set from Display Format under Setup.

You might also be able to get it on the Trip Computer, via Change Data
Fields.

David

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Mar 3, 2020, 7:47:53 AM3/3/20
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On Tue, 18 Feb 2020 13:39:47 +0000, Stewart Robert Hinsley wrote:

> On 13/02/2020 11:55, Stewart Robert Hinsley wrote:
>> On 11/02/2020 15:04, David wrote:
<snip>
>>
>>
> * The manual that comes with it doesn't provide any instructions as to
> how to persuade an Android device to pick up the output from this.
> Fortunately I has previously found the FAQ on Garmin's web site that
> explained how to do this.
<snip>

This is an area I was wondering about.
Briefly, (assuming that you are using the O/S App) do you have to convince
Android or the App? Or both?

I am considering a wireless GPS receiver/logger rather than a SatNav
device and the tablet and/or App would need to recognise this as a GPS
source.

Stewart Robert Hinsley

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Mar 3, 2020, 9:38:21 AM3/3/20
to
On 03/03/2020 12:47, David wrote:
> On Tue, 18 Feb 2020 13:39:47 +0000, Stewart Robert Hinsley wrote:
>
>> On 13/02/2020 11:55, Stewart Robert Hinsley wrote:
>>> On 11/02/2020 15:04, David wrote:
> <snip>
>>>
>>>
>> * The manual that comes with it doesn't provide any instructions as to
>> how to persuade an Android device to pick up the output from this.
>> Fortunately I has previously found the FAQ on Garmin's web site that
>> explained how to do this.
> <snip>
>
> This is an area I was wondering about.
> Briefly, (assuming that you are using the O/S App) do you have to convince
> Android or the App? Or both?
>
> I am considering a wireless GPS receiver/logger rather than a SatNav
> device and the tablet and/or App would need to recognise this as a GPS
> source.

It seems that OS Maps takes Android at its word.

You have to find a Bluetooth GPS app (Garmin recommend one called
Bluetooth GPS). This talks over the appropriate protocol (NMEA) with the
logger. You have to configure Android to enable mock location providers
(mock apparently means 3rd party, rather than fake instead of real). All
the apps I tried seem to happily work with the improved location
service, but I've read reports of some apps which don't.

I using OS Maps, a Grid Reference display/paste app, and a track logger,
and I've tried a second track logger successfully.

>
> Cheers
>
>
>
> Dave R
>
>

Stewart Robert Hinsley

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Mar 3, 2020, 9:59:47 AM3/3/20
to
Potential source of confusion - my tablet has native GPS. That the other
apps are using the bluetooth GPS is obvious from the improved accuracy,
but I wouldn't necessarily notice the difference on OS Maps. I've gone
to Settings/Location/Mode and turned off the native GPS, so if Android
is telling the truth OS Maps is only using WIFI and mobile networks for
location. (The choices are WIFI/mobile networks, device GPS, or both,
and it's not explicit how a mock location provide service is handled. My
tablet doesn't have mobile network access, and while the weather
conditions means I've not been far from housing, I've been without
logged on WIFI, and I expect that I've been far enough away at time
there were no WIFI routers in range even if - I don't know what is true
- WIFI routers give away location data to any passing device that I've
been out a range at times. On the other hand I've hardly used the OS
maps app. Bottom line - I can't be 100% sure that I would have noticed
if the OS Maps app wasn't working with the Bluetooth GPS

I'll take a note to myself to turn on OS Maps route recording feature,
next time that I'm out. That should provide confirmation.

Stewart Robert Hinsley

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Mar 10, 2020, 4:39:19 PM3/10/20
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Yes - it does work with OS Maps.

Looking at the track it can drift out of accuracy - at one point it
drifted into a field on the other side of the canal. The Etrex 20
behaved the same way - occasionally drifting out of accuracy.

It's not as good indoors as I thought it was, but it is better that the
Etrex 20.

I've loaded up MapFactor Navigator for a Open Street Map based
navigation app. (I used to use NavFree but that won't start up on my
tablet any more.)

--
SRH
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