In dense urban areas like New York, you may loose contact of GPS signals.

Hence the wheel pulse input is vital, and also the calibration of the wheel pulse.

You need to go into the Service Menu, and confirm the following:

GPS almanac downloaded? Good is 'yes'
GPS PDOP value? Good is <2, typical is about 1.5
GPS signal strengths of satellites? Good is between 10 and 15, it will vary from satellite to satellite. I generally have 4 satellites with >10 S/N
Wheel pulses? Must change with speed, and show negative when going backwards.

To calibrate the wheel speed pulses requires good GPS reception, good PDOP, and then a few minutes of constant driving - motorway is easiest.

Don't expect calibration to work in the middle of a city! You need a road in a clear area with unobstructed GPS reception

Jochen

well you can see by my images that my signal strength is good. when i was downtown, the problem wasn't that i lost signal, it's that it was putting me in the wrong place. the issue here is not position aquisition. it's that it's giving me the wrong location. when i had my mk3 navi in, i had absolutely no problems in new york or anywhere else. i'm gonna put that navi back tonight in to see how it is

anyone have any other ideas?

What images? None posted...

Remeber: you can have strong signal strength but poor positional accuracy - that's why you need to chec your PDOP value

the images are on the previous page. my PDOP bounces between 2 and 5 during driving. i just put in my old mk3 navi and it started giving me accurate position after about 5 minutes of street driving. i've driven a good 100 miles mixed city/highway on the mk4 navi and still it sucks. could it just be a bad receiver?

Your old Mk3 was still calibrated to your car.

To test the receiver accuracy, park the car, note the level of GPS PDOP with the Mk3, and write down the lat(long from the service menu

Then fit the Mk4 without moving the car, and wait for it to acquire good GPS position

Compare the two.

I'd guess the GPS receiver is OK but maybe the gyro is faulty... what does the gyro say? It should have a mid value of around 2500 mV, and go up when turning right (to over 3000) and down when turning left (to <2000), and stable at 2500 when going straight ahead.

Or otherwise the speed pulses are not yet calibrated... compare your speed pulse readings with another Mk4 in a similar car (do you have an X5?)

Jochen

I have a similar problem on my Aus 04 X5 with retro fitted Mk4. My car alrady had the factory fitted screen, tv tuner & nav wiring. I just fitted the Mk4 & a BMW GPS antenna.

My position is laggy, always about 50M behind and it never catches up even when stationary, all my sensors seem to work and it accurately plots my position in tunnels.

My position is always on a road and never strays off road on top of a house, etc.

I imagine that what I have is normal operation for a Mk4?

I will check the gyro tonight. but does it really need all that? i have a bluetooth gps receiver hooked up to a PDA and it works perfectly fine. even aquires a signal faster. doesn't need a gyro or any wheel speed sensor. it just picks up a signal and knows where you are by that.

i have an M3 and i'm gonna try swapping the unit with another m3 to see if it will make a difference

I hate to say this, but having the wheel sensors and gyro improve the accuracy :rolleyes:

It allows the Navi Computer to continue calculating vehicle position during moments of GPS signal loss.

Just as a thought, have you tried using the nav option to reposition the pointer - I cannot recall exactly which option it is (you get at it from map mode if I remember correctly), but it allows you to set the pointer at say a known road junction, and then when you drive over that point, you press the command knob and it supposedly latches your vehicle position to the pointer position.

I used to have to keep doing this when I had the wheel sensor problem, but it does drift out quite quickly.

Your PDA is just a GPS receiver

The BMW nav is an inertial guidance system with GPS position verification - quite different!

Your PDA won't work in tunnels, in parking garages, etc.
The BMW nav will.

Ok i put on abuot 70 miles today. Most of which was highway driving at 60+ and it's still doing exactly the same thing. Can I rule this as a faulty receiver?