Sat Nav position query

McMasters · 20th October 2009, 16:21

Hi.
I have just replaced a very temperamental disk spitting Mk2 with a Mk3 ( BMW with a nice Rover75 splash) .
All works well and seemed OK but ...

I noticed an odd thing when I turn a corner or change direction.
The voice asks to return to planned route and the direction arrow starts turning in all directions,flashing up various short meter distances, eg 40, 60, 30, etc
When I look at the map ( split screen) the position of the car seems to be approx. 50 meters beyond the route intersection.???? Some times it asks for a U turn after I have turned into the right street??? Then after a 100 meters or so the correct distance to the location appears again. On long stretches it runs OK but as soon as I change direction in small street areas... or near a corner , it starts getting loopy. I have tested it with known destinations and tried different route settings.
It always get you there but

on freeway turnoffs I can see a problem as is stops tracking just when one needs the right info.
Can the positioning be made more accurate, this over run seems like a distance problem when the unit takes new readings.

Any tips from the Sat Nav specialist most welcome.

damydyo1 · 20th October 2009, 21:23

Hello Neil,

Try this: When your car was disconnected from the battery for a while, your navigation could fail in finding the right car position. Don't ask me why, because normally your navsat is guided by 6 to 8 satelites. For this I put a pdf in the attachment in which you can find how to set the correct vehicle position. Look for the last pages 32 and 33.
Let me know if this worked out for you.

Regards Ralph

ChineseRover · 20th October 2009, 23:25

Suspect the compass is not working as the unit is not recognising your change of direction and is assuming you are travelling in the old direction until it works out the position from recalculating position via GPS.
The system does a lot of "dead reckoning", particularly in town when building might be blocking the sat signals.

Had this problem when the car was new (first week) and the sat nav computer was replaced.

McMasters · 21st October 2009, 05:41

Thanks guys will have a look at that and report back. I have a Mk3 BMW unit and the menu looks different from the one in the attachment. That looks like my old Mk2 menu.
One other question.
I upgraded from a Mk2 to a Mk3. The "how to" posts said to just swap the antenna cable from the little silver box mounted over the old Mk2 Sat nav unit and plug it into the new Mk3 unit, Which I did. Should I also disconnect the black plug from the little silver unit that formally housed the cable or just leave it connected????

Reebs · 21st October 2009, 11:23

Quote:

Originally Posted by McMasters

Thanks guys will have a look at that and report back. I have a Mk3 BMW unit and the menu looks different from the one in the attachment. That looks like my old Mk2 menu.
One other question.
I upgraded from a Mk2 to a Mk3. The "how to" posts said to just swap the antenna cable from the little silver box mounted over the old Mk2 Sat nav unit and plug it into the new Mk3 unit, Which I did. Should I also disconnect the black plug from the little silver unit that formally housed the cable or just leave it connected????

Yes disconnect the plug from the Mark 2's GPS receiver, and tuck it away so it doesn't rattle, the GPS receiver should be completely out of circuit, as the Mark 3 has one of it's own already built in. This may be the cause of your issues.

Departed · 21st October 2009, 21:02

Quote:

Originally Posted by ChineseRover

Suspect the compass is not working as the unit is not recognising your change of direction and is assuming you are travelling in the old direction until it works out the position from recalculating position via GPS.
The system does a lot of "dead reckoning", particularly in town when building might be blocking the sat signals.

Had this problem when the car was new (first week) and the sat nav computer was replaced.

There isn't actually a compass in the system.

You are dead right it does dead reckoning, but it uses wheelspeed pulses and an accelerometer to do this, no compass.

McMasters · 22nd October 2009, 09:42

Well I disconnected black plug from the "Trimble" Mk2 receiver , ran the service mode menu , no errors found, tracking all satellites , direction forward position correct etc etc etc . All OK it seemed mmmm

So, another test drive, known route. Set the map scale to 500m instead of 200m just in case that was an issue.
Anyway it seemed a lot better snappy, less confused at the corners. Meter countdown seemed pretty good, the first screen refresh after the corner also good. But at one spot near the last turn it got confused again and said 'please return to the planned route' and spun the direction arrow around in several positions with various distances 100 m 50 m 30 m etc. I proceeded on the correct road then finally it kicked in with the right info and direction again till we arrived at the destination. Perhaps it is a satellite blind spot on that corner????

So thats the update report folks. Not perfect but better. I just hope it doesn't spit the dummy on the autobarn turn offs

Kearton · 25th October 2009, 12:36

It may just be that the connection from the GPS antenna into the sat. nav unit is not fitted in tightly enough. That happened to me once. A simple enough thing to test.

Kearton

McMasters · 26th October 2009, 11:12

Thanks Kearton
Checked the GPS antenna was fitted properly, is seemed to be OK but I unplugged it and plugged it back in just to be sure.

Test drive again, known destination and route. Still a few spots where the unit lost the plot and started to demand I return to the known route and a few spinning direction arrows with various meter distances. MMMMMMMM???

.

I think it is as if it is suddenly off the road in its position reading. I changed the scale down to 100m and bingo, the car position was not on the road but off it by 20 meters (rough guess as I was driving). The route was highlighted in white on the road map, the blue car pointer was in the middle of the paddock beside. Not on the road map route .

When in the scale is 200 or 500m you can't tell. It then seems to find itself or assume it is near enough to the route again and starts instruction as per normal. I used the service menu and it has no error noted and the wheel speed sensor and satellite check, all working. 6 to 8 satellites most of the time.
Does anyone know why it would track off the road then find itself again?

hans.schaaper · 27th October 2009, 12:32

ChineseRover already suggested a faulty gyro.
This is not a real gyro but a so called "rate of turn" sensor.
By means of numerical integration in time the navcomputer calculates "rapid" changes in the car's direction of travel.
This greatly improves the accuracy of position during turning.
The absolute direction of travel is computed from a number of gps position updates.

To check the "gyro" go into the <Service menu>
1. Select <Set> in the main menu.
2. Press the <Menu> button and keep pressed until the service menu pops up.
3. Select <Sensor check>

Observe the Gyro value being displayed.
With the car stationary (not turning) the value reads 02450 approx.
During turns the value either drops or increases depending on the direction of the turn(left or right).
When back on the straight the value returns to the stationary value.

How this helps.

20th October 2009, 16:21	#1
McMasters Avid contributor Rover 75 V6 2.5 Celeste LHD Join Date: Nov 2006 Location: Hamburg Posts: 207 Thanks: 0 Thanked 0 Times in 0 Posts	Sat Nav position query Hi. I have just replaced a very temperamental disk spitting Mk2 with a Mk3 ( BMW with a nice Rover75 splash) . All works well and seemed OK but ... I noticed an odd thing when I turn a corner or change direction. The voice asks to return to planned route and the direction arrow starts turning in all directions,flashing up various short meter distances, eg 40, 60, 30, etc When I look at the map ( split screen) the position of the car seems to be approx. 50 meters beyond the route intersection.???? Some times it asks for a U turn after I have turned into the right street??? Then after a 100 meters or so the correct distance to the location appears again. On long stretches it runs OK but as soon as I change direction in small street areas... or near a corner , it starts getting loopy. I have tested it with known destinations and tried different route settings. It always get you there but on freeway turnoffs I can see a problem as is stops tracking just when one needs the right info. Can the positioning be made more accurate, this over run seems like a distance problem when the unit takes new readings. Any tips from the Sat Nav specialist most welcome. __________________ [SIGPIC][/SIGPIC]

21st October 2009, 05:41	#4
McMasters Avid contributor Rover 75 V6 2.5 Celeste LHD Join Date: Nov 2006 Location: Hamburg Posts: 207 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks guys will have a look at that and report back. I have a Mk3 BMW unit and the menu looks different from the one in the attachment. That looks like my old Mk2 menu. One other question. I upgraded from a Mk2 to a Mk3. The "how to" posts said to just swap the antenna cable from the little silver box mounted over the old Mk2 Sat nav unit and plug it into the new Mk3 unit, Which I did. Should I also disconnect the black plug from the little silver unit that formally housed the cable or just leave it connected???? __________________ [SIGPIC][/SIGPIC]

22nd October 2009, 09:42	#7
McMasters Avid contributor Rover 75 V6 2.5 Celeste LHD Join Date: Nov 2006 Location: Hamburg Posts: 207 Thanks: 0 Thanked 0 Times in 0 Posts	Better but ! Well I disconnected black plug from the "Trimble" Mk2 receiver , ran the service mode menu , no errors found, tracking all satellites , direction forward position correct etc etc etc . All OK it seemed mmmm So, another test drive, known route. Set the map scale to 500m instead of 200m just in case that was an issue. Anyway it seemed a lot better snappy, less confused at the corners. Meter countdown seemed pretty good, the first screen refresh after the corner also good. But at one spot near the last turn it got confused again and said 'please return to the planned route' and spun the direction arrow around in several positions with various distances 100 m 50 m 30 m etc. I proceeded on the correct road then finally it kicked in with the right info and direction again till we arrived at the destination. Perhaps it is a satellite blind spot on that corner???? So thats the update report folks. Not perfect but better. I just hope it doesn't spit the dummy on the autobarn turn offs __________________ [SIGPIC][/SIGPIC]

26th October 2009, 11:12	#9
McMasters Avid contributor Rover 75 V6 2.5 Celeste LHD Join Date: Nov 2006 Location: Hamburg Posts: 207 Thanks: 0 Thanked 0 Times in 0 Posts	Off road experience!!!!!! Thanks Kearton Checked the GPS antenna was fitted properly, is seemed to be OK but I unplugged it and plugged it back in just to be sure. Test drive again, known destination and route. Still a few spots where the unit lost the plot and started to demand I return to the known route and a few spinning direction arrows with various meter distances. MMMMMMMM???. I think it is as if it is suddenly off the road in its position reading. I changed the scale down to 100m and bingo, the car position was not on the road but off it by 20 meters (rough guess as I was driving). The route was highlighted in white on the road map, the blue car pointer was in the middle of the paddock beside. Not on the road map route . When in the scale is 200 or 500m you can't tell. It then seems to find itself or assume it is near enough to the route again and starts instruction as per normal. I used the service menu and it has no error noted and the wheel speed sensor and satellite check, all working. 6 to 8 satellites most of the time. Does anyone know why it would track off the road then find itself again? __________________ [SIGPIC][/SIGPIC] Last edited by McMasters; 26th October 2009 at 11:17..

20th October 2009, 23:25	#3
ChineseRover Banned Rover 75 2.5 Conn automatic Join Date: Feb 2009 Location: London Posts: 152 Thanks: 0 Thanked 0 Times in 0 Posts	Suspect the compass is not working as the unit is not recognising your change of direction and is assuming you are travelling in the old direction until it works out the position from recalculating position via GPS. The system does a lot of "dead reckoning", particularly in town when building might be blocking the sat signals. Had this problem when the car was new (first week) and the sat nav computer was replaced.

25th October 2009, 12:36	#8
Kearton Gets stuck in MG ZT-T CDTi Join Date: Jul 2007 Location: Sunny Suffolk Posts: 617 Thanks: 1 Thanked 16 Times in 13 Posts	It may just be that the connection from the GPS antenna into the sat. nav unit is not fitted in tightly enough. That happened to me once. A simple enough thing to test. Kearton

27th October 2009, 12:32	#10
hans.schaaper Avid contributor rover 75 2.5 V6 auto Join Date: Feb 2008 Location: Alkmaar Posts: 197 Thanks: 0 Thanked 3 Times in 3 Posts	ChineseRover already suggested a faulty gyro. This is not a real gyro but a so called "rate of turn" sensor. By means of numerical integration in time the navcomputer calculates "rapid" changes in the car's direction of travel. This greatly improves the accuracy of position during turning. The absolute direction of travel is computed from a number of gps position updates. To check the "gyro" go into the <Service menu> 1. Select <Set> in the main menu. 2. Press the <Menu> button and keep pressed until the service menu pops up. 3. Select <Sensor check> Observe the Gyro value being displayed. With the car stationary (not turning) the value reads 02450 approx. During turns the value either drops or increases depending on the direction of the turn(left or right). When back on the straight the value returns to the stationary value. How this helps.