tracking on the new app

Hi Phil

You are probably correct but the lack of GPS satellite visibility is often just the start of the problem. A lot depends on the functionality embedded in the GPS chips. I ran a big survey company for many years and probably know enough to be dangerous on the subject. So for what it's worth here goes.

1 GPS coverage over Australia is quite poor compared to North America and Europe. If you really want decent coverage here you need a GPS chip that "sees" Glonass (Russian) and GPS satellites. It is very unlikely that these chips are in consumer devices.

2 Each GPS satellite has a unique orbit and identifier. A GPS chip may or may not have the capability of updating this empheris detail. If not the chip takes a long time to find a satellite and to calculate where it is on the WGS84 spheroid. So if you lose GPS lock and are on the move the chip may be looking for satellites that are now out of view.

3 Each chip set has different setup parameters. I have no knowledge of the defaults that have been setup in consumer products but I would expect there is a timeout function to save power. This may cause the chip to stop searching for sats until the next power up. Also the manufactures of the chipset will change the setup depending on its application. eg parameters will be different if your walking around vs flying in a jet. Where you may be will be very different in one minutes time.

4 The GPS signal is incredibly weak. It lives within the "white noise" frequency of background radio. The interior of a car is a very noisy environment and as you have stated the windscreen and car direction of travel limits the GPS view significantly. Dedicated car navigation GPS units use historical trajectories and internal logic to synthesise positions when GPS position ( at least 3 sats in view) is lost. Such functionality is not likely to be in consumer products not designed for navigation.

To be frank I am amazed at how will these cheap GPS chipsets work in a car without an external antenna. The rural environment is the best where man made infrastructure, that causes multipathing etc is least, provided that you are not in heavily forested or mountainous country that obscure the view to the satellites.

Having had similar problems to the author of the thread I have generally solved the problem by taking the device out of the car, allowing it a good view of the sky, and waiting until it re- establishes satellite lock, then moving off.

Hopefully this has been of some use to somebody.

Cheers John

Thanks John Too technical for me. The Backview dash cam does not have a problem and it's not worth the trouble to take the navigation box out of the dash.

Luckily it only happened at O'hagens camp.

Cheers

Phil

"If you really want decent coverage here you need a GPS chip that "sees" Glonass (Russian) and GPS satellites. It is very unlikely that these chips are in consumer devices"

? All "consumer" devices with inbuilt GPS surely have a GPS chip that detects the US satelites as minimum....otherwise they probably wouldn't rate as a "GPS":)

I also think you will find many current model gps units made by main manufacturers (Garmin, Magellan) also have the added bonus of Glonass. Garmins certainly do.

Some Samsung Galaxy Tabs also have Glonass. Could be others ....haven't done a full review and never will :)

So ..dont assume "consumer devices" dont have GPS and Glonass, as many do as far as I can figure.

Cheers
Greg

.....just checked and even my old Samsung S5 phone has "GPS, Glonass, Beidou"....No idea what Beidou is....

Cheers
Greg

Oh Beidou is the Chinese gps sats. ...more satelites up there now than you can poke a stick at.

Cheers
Greg

J&A&KK posted: "I ran a big survey company for many years and probably know enough to be dangerous on the subject. So for what it's worth here goes.

1 GPS coverage over Australia is quite poor compared to North America and Europe. If you really want decent coverage here you need a GPS chip that "sees" Glonass (Russian) and GPS satellites. It is very unlikely that these chips are in consumer devices. SNIP"

John, this is not correct.

The coverage at any latitude is the same as other locations at that latitude and also the same at the opposite latitude. Ie coverage at 33 degrees N is the same as 33 degrees south. The sats rotate and change position, covering the entire earth almost equally based on lingtitude. The poles get better coverage than the equator.

As to Glonass, it would be hard to buy a consumer device without it, this has been the case for 4 or more years. Iphone introduced it from 2012 in the Iphone 4s ( and all models after that) and Samsung introduced it in models from the late 2012. Most phones would have GPS, Glonass and Bedou ( chinese) now.

Hi

There are probably some areas with better GPS coverage than others given that, as discussed, various countries have launched their own satellites (besides US), some with concentrations over particular areas...but more than enough over Australia at any one time, so hard to see how coverage would be rated as "poor".

Just went outside with the Samsung Galaxy Tab (10.1) and using app called GPS Status, picked up 16 satellites. 8 were US satellites, 7 Glonass and 1 QZSS (Quasi-Zenith Satellite System - Japanese time-transfer system, to augment GPS ??). No Chinese ones...may need different antenna/chip.



A bit later tried the Samsung Galaxy S5 phone - picked up 32 satellites!!...but only got a "fix" on 17. The additional satellites were the Chinese Beidou ones (the phone obviously has a different GPS chip to tablet)...but these Sats (Number 201 and above) didn't seem to be providing any location information as indicated by grey colour.



You can tell which "group" each satellite belongs too based on number (NMEA) IDs which are "roughly" (?) divided into the following ranges:

1–32: GPS
33–54: Various SBAS systems (EGNOS, WAAS, SDCM, GAGAN, MSAS)
55–64: not used (might be assigned to further SBAS systems)
65–88: GLONASS
89–96: GLONASS (future extensions?)
97–192: not used
193–195: QZSS
196–200: QZSS (future extensions?)
201–235: Beidou

All good fun

Cheers
Greg

Hi All

Thanks to everyone for the education. Always interesting and informative feedback.

Questions are still raised as to how a consumer device loses "position" when it can see and use 17 satellites (per Gregs informative input). This is of course assuming that the majority of consumer devices have similar capability to the Samsung S5.

An interesting technical discourse. I am updated and remain dangerous.

Cheers John

Hello John

Good to see you have a sense of humour - some people on the forum seem to lack it almost completely, but enough about me ...

Its can be hard keeping up with technology. I am way behind on the GPS stuff. My favourite GPS which I use for work only picks up the normal "GPS" sats (though still does job adequately) and haven't until now bothered even thinking about Glonass etc etc - didn't even know about the Chinese Japanese ones.

Anyway as far as the OP's (Jim's) apparent problem, still a bit of a mystery - could be a number of things. Jim does state that "The app locked up a few times" which I would presume would result in track logging also stopping - explanation right there (but what caused app to lock up?).

He also states that the app "seemed to stop checking the gps position", which implies the app is again malfunctioning but use of the word "seemed:' is not convincing proof.

I am also unsure what he means by "I had a signal most of the time, as I carry a modem". I wonder what "signal" he means - GPS or Phone? So a bit confusing.

Would suggest some more bug testing to see if the problem can be isolated to the app or the tablet/GPS. I am beginning to think the app is freezing for some reason...but could be occasional loss of actual GPS signal for one reason or another, though I think this is less likely, especially if the tablet was in a reasonably good position to get view of sky. After all, you only need 4 sats.

Cheers
Greg

ExploreOz Traveller, the one seen in this forum (and sold by Explore Oz)
for the last few months. Nearly everyone has seen the multiple write ups so I didnt think it was necessary to name it, but there you go. Some people cant do forums without the pushy -pushy
Any problems are pointed at the forum so the writer of the app has the ability to answer, and the results seen by all. - so as not to get repeats. Different devices have different issues with any new app, and my comments on a new app on a 10,000 klm run would be relevant, any reasonable person would think.

Sounds like it's that tracking thingumy Pater.

The symptoms are just like here with the dash cam in the home car. Sometimes the navigation unit in the car fails to link when we are down in the depths of the high country. The track on Ozi gets straight lines while the signal was lost.

Phil

Some also ask questions and dont provide enough info because they think people will know what they are thinking. Not all readers read every thread and all are different in their own way.
If you state the name of what you are talking about you wouldnt get replies like above. Its not too much to ask I dont think.

Easier than trying to guess what you MIGHT mean.

Michelle
thanks for the reply. I used the wrong terminology, this relates only to logging. I am a member, have bought the app, and have the "enable track logging" switch on. However several times on the trip, it semed to stop looking for the satellites, or couldnt find them. We didnt move the tablet in the car too much, I cant believe that it suddenly couldnt see the satellites? Check my recent track from Cairns to karratha and back, - several straight lines?
If it was the device that couldnt find the gps position, wouldnt it issue a notification? So am I right in assuming it was the app was locked up?
Thanks
Jim

Just what I was thinking Michelle
GPS dropout = straight lines