GPS psoition not exactly 25 to 50m difference

[pklein90]

Hello,

my gps has no right position i think the difference is between 25 to 50 m :mad:

Is there a tool to correct this issue ?

Thx

Nochmal in deutsch falls mein Englisch nicht so gut zu verstehen ist ;)


Mein GPS im Artemis hinkt etwa 25 bis 50 m hinterher was sehr nervig ist :(
Kennt jemand dieses Problem und weiß wie man Abhilfe schafft ?

[spangelsaregreat]

From what I recall no civilian GPS is precisely correct.

Only Military GPS is precise to the metre.

Not sure what the exact varience is though.

Regards

[pklein90]

i have navigation systems before the p3300 and on all when the street cross comes it brings exactly the position when it says turn left at 50m then it was correct, i believe the military difference is only 1m or lower not 50m ???

For external PC gps receiver there is a software for correct some options for the inbuild gps.
I have no glue for a in built gps.


Sorry for the English this not my normal language, i hope you can understand what i mean thanks ;)

[zerimar]

Also, better accuracy depends on the number of satellite signals the device can get. Signal strength is weaker in the urban areas.

[mikealder]

What software application are you using when you notice the discrepancy? I have found my Artemis GPS position to be equal to some of my other units. For example using a topographical map when out walking the unit is very good, certainly not 25 to 50 M out. It could be low signal strength and reflections off other building that is causing a problem (if in built up area)

One other consideration, how many other applications do you have running at the same time as your Nav software, your device might be struggling under load, check settings/ system tab Memory icon/ running programs and stop all before trying the nav software Mike

[zerimar]

My device, which is still the Magician is running the ROM 1.13 with BS. Additional software which are all installed in the Storage are; Pocket Informant, Photo Contacts Pro, Resco Suit, SK Tools, TT6, WorldMate Pro, Ring tones. All TT maps (WEU, USA+Canada), voices, schemes, zip codes, POIs and IE Temporaty files are installed in a 2GB SD. What's left in available memory are Storage = 0.7 of 26.72 MB, Storage Card = 105 MB of 1935GB.

The programs that are running (being memory resident) while TT6 is active are Photo Contacts Pro and Pocket Informant. I have BT on all the time since I use a BT headset for calls while driving. TT audio is via my Seidio active car holder.

[pklein90]

The programm ist TT6 and only jetware, and ilauncher active nothing more, the area is no big city good sight to the air.

I checkt this with tt5 and a hp2210 with bluetooth sirfIII this combination is near perfect :D

[zerimar]

I've never used those programs. The inaccuracy might come from any of the two.

[Samson711]

Civilian GPS is officially (from the provider of the GPS System - US Forces) something about 10 metres unexact. Of course this number can be smaller if you have more satelites "in sight" However, GPS Navigation Programs do not need accurate positions, they calculate the position on the map with old data and then extrapolate it, showing the dot where you should be now, according to your speed and heading 1 second or two seconds ago. Of course it can control its calculation because more data streams in. It is funny to see Navigationsoftware Confused, when you ride a train. It gets a signal in a certain direction, with a certain speed, so it puts the dot on the street next to the Rails, because this is the only logical position where your car can be :) so it says "turn left now" but the train goes straight. Then it searches another street you could be on. just funny ;)
But in short: GPS Software compensates missing GPS accuracy, mostly well, sometimes not so good. Try using another Software or newer map ,maybe that will fix the problem. On my MDA Compact III The Built in Receiver works just great together with TT6. Maybe there is a way to shorten the interval between two data sets. That would give the Software more information, resulting in a more accurate position. But i don't know if a program like GPS Maus can manipulate Built-In receivers that easy.
I once reprogrammed a T-Mobile Receiver with this program, so it received also NMEA data and the intervall between two data sets could be set randomly.

[jthspace]

In the UK, the BBC send out a spoiling signal which reduces the accuracy of the GPS. It is also sent out from National stations in other Countries. I heard it was sent out with the atomic clock signal. This is to stop "undesirables" buying civilian GPS units and fitting them to military equipment and sending something directly to your letterbox - the same way a US military GPS unit can if they want to! You used to be able to buy a box that would correct the error signal, but that got stopped ages ago.

The GPS also becomes slightly more inaccurate depending on the speed you are travelling, travel under 30 mph / 50 kph and the "you have arrived" will be within a few yards/metres of the real arrival point. Travel at 70 mph / 120 kph and the "take the exit in 200 metres" is very inaccurate - maybe by a couple of hundred metres - you can work out why!

Also GPS signals are "secondary" and can be turned off at any time in the event of a military requirement - which is why you can use the signals free of charge.

Jeff

[mikealder]

In the UK, the BBC send out a spoiling signal which reduces the accuracy of the GPS. It is also sent out from National stations in other Countries. I heard it was sent out with the atomic clock signal.

Where did you get this gem of knowledge from?

This is to stop "undesirables" buying civilian GPS units and fitting them to military equipment and sending something directly to your letterbox - the same way a US military GPS unit can if they want to! You used to be able to buy a box that would correct the error signal, but that got stopped ages ago.Are you confusing the selective availability that was used to degrade the GPS accuracy up to a few years ago? - The US reserve the right to switch it back on again should they need to, but under normal conditions the signal is not de-graded any longer. If you want to send something to a letterbox the Post Office offer quite a good service ;)

The GPS also becomes slightly more inaccurate depending on the speed you are travelling, travel under 30 mph / 50 kph and the "you have arrived" will be within a few yards/metres of the real arrival point. Travel at 70 mph / 120 kph and the "take the exit in 200 metres" is very inaccurate - maybe by a couple of hundred metres - you can work out why! The issue of position inaccuracy relative to speed won't give a major difference to position - the software maybe responsible for the apparent degradation though.

Also GPS signals are "secondary" and can be turned off at any time in the event of a military requirement - which is why you can use the signals free of charge.As I mentioned before the US reserve the right to turn on the Selective availability (positional accuracy degradation), if they turn it off their own planes and other civ/ mil products would be useless - Mike

[jthspace]

Where did you get this gem of knowledge from?



When I worked on the original GPS launches a while back

Jeff

[CouchPotato]

In Artemis is a Sirf-III-Chipset. One of the "features" of this chipset is a Parameter called "Static navigation".
This gives a more or less "static" position if the device is moving rather slow, like a pedestrian does.
Useful for car navigation because your car is not "dancing in front of the traffic light".

But it gives a more or less not accurate position when standing or moving rather slow. You need to move with 5 Km/h at least.

No tool for switching off "Static Navigation" in Artemis seems to be working. :(

[allenf]

Selective Availability:
"SA works, for the most part, by intentionally dithering the clocks in the 24 satellites that make up the GPS system. The clocks are steered by an algorithm, known to the control station and military receivers and transmitted in encrypted code over the satellite signals."
http://www.exn.ca/FlightDeck/News/story.cfm?ID=20000502-53

[nixonm]

The BBC does what??? I don't believe that for a moment!

The GPS signal I get on my Orbit and previously on my Fortuna Clipon has been extremely accurate, using different software Tomtom 5 & 6, pocket streets and Vito all have been down to a couple of meters at most.

I have also used in the US, Cyprus and Spain all with the same accurate results.

Yes the US can turn off civilian GPS if they wish, which is why the EU is building Galileo.

[madcow_x2]

interesting to see people still talking about SA, it has been switch off since year 2000!

http://www.ngs.noaa.gov/FGCS/info/sans_SA/