navi showing incorrect position
 

I just installed an MK4 navi drive in my 02 M3. Everything works well and it navigates and all that. The only problem is that the position it plots me on the map is off. For example, if I completely cross an intersection and look at the map, it will show me as coming up to the intersection. This can be very confusing when streets are very close together. It's approximately 100 feet west southwest of where i should be. When I drive down my block, the map will show me driving in between the two streets instead of on my street.

anyone had this problem or have any ideas?

If the nav came from another vehicle, then it needs to adapt itself to your car. To do that, go for a drive on the autobahn / motorway for at least 15min, driving at around 60mph / 100kmph. After a few minutes the nav will be calibrated to your wheel size (it adjusts the calibration valus to match your vehicle speed to GPS calculated vehicle speed).

thanks for the info. however i have already been driving around the entire day yesterday, both on streets and on the highway, i dunno if i went at least 60 for 15 mins straight, but it was definitely alot of driving. you think i need more time for it to adjust or could the unit be faulty? i was gonna put my old unit back in to see if it goes back to normal.

Go into the hidden 'service' menu and check that the Wheel Sensor field is changing with speed - if not (it shows 0 or is static when you are driving) then it is probably a faulty (incorrectly pinned) loom. I had this on my E46.

See http://www.xoutpost.com/articles/all-...formation.html for some info

this seems to be only for people who retrofitted the navi. mine was stock and my mk3 nav worked perfectly. but i will check out if the wheel speed sensor changes or not.

Hey have you tried to input directions just to see what it will do??

yea i have. and i did it while i was downtown manhattan where the streets are criss crossed and really close together, it really messed me up. it blatantly put me on the strong street. i had to look at the map and figure it out on my own.

It was down to a set of faulty wiring looms - some went to factory fit, some went to retrofit. It seems that people who retrofitted noticed the problem. My E46 had this exact issue and it took about 6 visits to the dealer to resolve, and only because I found the info about the wheel sensor wire did it get fixed.

But it may be something totally different in your case, however unlike the early Mk's of navi computer, the Mk4 has no dealer calibrations - it takes all the data from the GPS and the inertial sensors in the car (gyro, speed and direction etc) to calibrate

Can you go into the navigation service menu and tell us what all of the GPS status information is showing. Maybe we can figure out something from that data.

i attached the images here. some of them are blurry but you can make out what it says. in the first picture you can see the gps plotted me on top of someone's house (in between streets).

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?

My guess would be the GPS reference clock is out.

You can try by replacing the GPS receiver (it simply plugs in) - try swapping it from the good Mk3 to the new (bad) Mk4 and see if it makes a diference.

If the replacement GPS receiver doesn't fix it then the problem is on the main board - maybe there is a reference clock which is off-frequency.

You could consider sending it to VDO in Wetzler Germany for repair, or sell it for spare parts.

Regards, Jochen

where is the gps receiver? is it inside the unit?

Yes, take the top lid off, and you can see the GPS receiver as a metal-cased module. It is physically held on by the nut on the GPS antenna connector.

Take the nut and washer off the antenna connector, unplug the wiring connector on the GPS receiver, and it comes out quite easily.

Sounds like multipath error (http://en.wikipedia.org/wiki/Global_Positioning_System#Multipath_effects). Check your antenna, and also see if the problem persists when there are no buildings around.

Won't the GPS unit always synchronise its time with the atomic clock in one of the GPS satellites? (http://en.wikipedia.org/wiki/Global_..._time_and_date)

I understood that local clock errors can contribute to GPS error

But maybe I am wrong...??

Did the OP ever get this resolved? Would like to know the answer.

nope. i just put my old unit back in