Going fast enough to loose GPS signal?
Discussion
Had a weird thing recently when in Germany. Making use of the autobahns in a 2007 BMW E93 with iDrive with Pro nav. Going quite fast obviously and the signal would drop out and put the location somewhere not on the road. I wondered if perhaps the road been moved hence not matching up with the map or indeed the signal was affected due to the speed. Just a hiccup on the iDrive? Anyone else encountered this?
Thermobaric said:
Had a weird thing recently when in Germany. Making use of the autobahns in a 2007 BMW E93 with iDrive with Pro nav. Going quite fast obviously and the signal would drop out and put the location somewhere not on the road. I wondered if perhaps the road been moved hence not matching up with the map or indeed the signal was affected due to the speed. Just a hiccup on the iDrive? Anyone else encountered this?
Don't know anything about the GPS in the E93, but my E46 330Ci never lost its GPS signal on the built in nav even when at V-max on the Autobahn. My phone GPS also seems to work correctly even when cruising in an airliner, so I doubt speed alone is a factor.Itsallicanafford said:
M3 CSL on the autobahn...180mph on the clock, Garmin confirmed the actual speed of 167mph when we hit the soft limiter
They still have a good bit to go after that when unrestricted, probably another 10-15mph judging by the difference to another CSL that hit its limiter. Speedo was off the clocks in mineRemember the phone GPS giving up the ghost at 160+
No it has been known.
You get Doppler effect depending on the angle between the satellite and the car. Clearly the Doppler is more effected by speed, and the GPS frequency changes.
Since the information is mainly transferred by frequency, it's possible that there is a positional error on the car.
Mind you it does depend on the relative position of the car and the satellite. If it's side on, or you are heading towards it, the effect is much less severe, and the inaccuracies much much less.
Just occasionally the angle of the windscreen will effect the frequency as well,and you completely lose the sat nav tracking.
You get Doppler effect depending on the angle between the satellite and the car. Clearly the Doppler is more effected by speed, and the GPS frequency changes.
Since the information is mainly transferred by frequency, it's possible that there is a positional error on the car.
Mind you it does depend on the relative position of the car and the satellite. If it's side on, or you are heading towards it, the effect is much less severe, and the inaccuracies much much less.
Just occasionally the angle of the windscreen will effect the frequency as well,and you completely lose the sat nav tracking.
bearman68 said:
No it has been known.
You get Doppler effect depending on the angle between the satellite and the car. Clearly the Doppler is more effected by speed, and the GPS frequency changes.
Since the information is mainly transferred by frequency, it's possible that there is a positional error on the car.
Mind you it does depend on the relative position of the car and the satellite. If it's side on, or you are heading towards it, the effect is much less severe, and the inaccuracies much much less.
Just occasionally the angle of the windscreen will effect the frequency as well,and you completely lose the sat nav tracking.
Probably a matter of how many sats are actually 'visible' to the receiver than anything else. IIRC it's a min 4 reqd for position, and 7 or more is optimal. It's a 1.58Ghz signal so quite easily shielded.You get Doppler effect depending on the angle between the satellite and the car. Clearly the Doppler is more effected by speed, and the GPS frequency changes.
Since the information is mainly transferred by frequency, it's possible that there is a positional error on the car.
Mind you it does depend on the relative position of the car and the satellite. If it's side on, or you are heading towards it, the effect is much less severe, and the inaccuracies much much less.
Just occasionally the angle of the windscreen will effect the frequency as well,and you completely lose the sat nav tracking.
bearman68 said:
No it has been known.
You get Doppler effect depending on the angle between the satellite and the car. Clearly the Doppler is more effected by speed, and the GPS frequency changes.
Since the information is mainly transferred by frequency, it's possible that there is a positional error on the car.
Mind you it does depend on the relative position of the car and the satellite. If it's side on, or you are heading towards it, the effect is much less severe, and the inaccuracies much much less.
Just occasionally the angle of the windscreen will effect the frequency as well,and you completely lose the sat nav tracking.
That's not how GPS works. It's not working out position by doppler shift and no speed you travel in a car, plane or rocket it going to be be high enough to doppler shift the signal so much that the GPS receiver can no longer lock on to the signal. GPS works by comparing an accurate internal clock and ephemeris data with a time signal received from the satellites to work out distance from each satellite, and from that a position is triangulated.You get Doppler effect depending on the angle between the satellite and the car. Clearly the Doppler is more effected by speed, and the GPS frequency changes.
Since the information is mainly transferred by frequency, it's possible that there is a positional error on the car.
Mind you it does depend on the relative position of the car and the satellite. If it's side on, or you are heading towards it, the effect is much less severe, and the inaccuracies much much less.
Just occasionally the angle of the windscreen will effect the frequency as well,and you completely lose the sat nav tracking.
GPS signals are incredibly weak and can easily be interfered with by local signal reflections from buildings, trees and geographical features such as mountains. The signals fade in and out in much the same way as an AM (or FM) radio signal does when you're at the limit of the range of the station transmitter. It's entirely possible that some of the satellites providing a positional fix can be transiently invisible, and that can cause the triangulated positional fix to wander.
Most road-oriented GPS systems have a map database, and when at speed the system will snap the vehicle position to a mapped road closest to the triangulated fix. That's why you can sometimes see the position marker travelling along the map on a road parallel to the one which you're actually on.
Sushifiend said:
That's not how GPS works. It's not working out position by doppler shift and no speed you travel in a car, plane or rocket it going to be be high enough to doppler shift the signal so much that the GPS receiver can no longer lock on to the signal. GPS works by comparing an accurate internal clock and ephemeris data with a time signal received from the satellites to work out distance from each satellite, and from that a position is triangulated.
GPS signals are incredibly weak and can easily be interfered with by local signal reflections from buildings, trees and geographical features such as mountains. The signals fade in and out in much the same way as an AM (or FM) radio signal does when you're at the limit of the range of the station transmitter. It's entirely possible that some of the satellites providing a positional fix can be transiently invisible, and that can cause the triangulated positional fix to wander.
Most road-oriented GPS systems have a map database, and when at speed the system will snap the vehicle position to a mapped road closest to the triangulated fix. That's why you can sometimes see the position marker travelling along the map on a road parallel to the one which you're actually on.
Sorry, was trolling a bit. I was wondering how long it would take for someone to pick me up on my obvious BS.GPS signals are incredibly weak and can easily be interfered with by local signal reflections from buildings, trees and geographical features such as mountains. The signals fade in and out in much the same way as an AM (or FM) radio signal does when you're at the limit of the range of the station transmitter. It's entirely possible that some of the satellites providing a positional fix can be transiently invisible, and that can cause the triangulated positional fix to wander.
Most road-oriented GPS systems have a map database, and when at speed the system will snap the vehicle position to a mapped road closest to the triangulated fix. That's why you can sometimes see the position marker travelling along the map on a road parallel to the one which you're actually on.
You're (probably) right, but it amused me for 24 hrs
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