Just getting the info together for sat-nav installation, and while I have everything I need in terms of mounting hardware and speedo signal, I need a 12v signal from the reverse lights so it knows which direction its going. Anyone know if it appears in the wring loom around the dash anywhere? or do I have to run a wire from the switch on the gearbox or the light clusters?
Thanks,
GSB.
I thought you were joking when I first read the post like 'what kind of sat nav system needs to be told when it's going forwards' but after I thought about it I guess that the unit is not necessarily installed in the vehicle in a particular direction :-) :-) :-)
crankshaft
Quote from: "crankshaft"'what kind of sat nav system needs to be told when it's going forwards'
I guess it must not use GPS for positioning? Odd.. I just plug mine into the cigarette lighter socket and off I go s;) ;) s;)
My guess on the reverse wire would be it being at the back of the car somewhere and not up front - I could imagine a neutral wire going to the ECU, though.. Which doesn't help you much. I'll shurrup now s:) :) s:)
Quote from: "aaronjb"Quote from: "crankshaft"'what kind of sat nav system needs to be told when it's going forwards'
I guess it must not use GPS for positioning? Odd.. I just plug mine into the cigarette lighter socket and off I go s;) ;) s;)
It uses GPS as its primary position feed, but to improve accuracy and speed, it also uses "Dead Reckoning" techniques to allow it to calculate position and direction faster than GPS alone would allow. It uses an onboard compass to calculate its orientation (GPS cannot tell you which way your facing, it can only tell in waht direction you came from.), and pulsed signal from your speedo, (Again, GPS wont tell you how fast your going "Now", just how fast you were going the last time it completed its measurements) Using Dead reckoning also allows it to calculate its poition much closer than GPS alone, down to about 2 feet in the right circumstances.
It also uses a reverse light signal, which in conjunction with the compass, allows to tell when your turning around. Sat Nav systems without this tend to take a short while to work out whats going on when you do that. s:shock: :shock: s:shock:
Quote from: "GSB"It also uses a reverse light signal, which in conjunction with the compass, allows to tell when your turning around. Sat Nav systems without this tend to take a short while to work out whats going on when you do that. s:shock: :shock: s:shock:
I can see the advantage of dead reckoning definitely - the downside of mine (just an iPaq with TomTom) is when it loses the sky in tunnels/wide bridges..
I've not noticed it have problems with me turning around though - although I presume it must have a compass built in as well, as it seems to know what direction I'm facing even if I haven't moved anywhere yet (when I've just plugged it in)
TomTom does take absolutely, positively an age to calculate routes though - the manufacturer fit system in a friends Laguna is much quicker s:( :( s:( Though I do get funky 3D maps s:) :) s:)
Anyway, not helping you find your wire, am I.. s:oops: :oops: s:oops:
*hides from any lurking mods*
I recently (5months) fitted an after-market GPS to my 2. ISTR at the time, that the method preferred at the time was to route the wire from behind the luggage boxes.
To be honest, I decided to leave it, and see how the system worked without it. In five months of fairly regular use, I have seen no negative effect to just leaving this wire unconnected - the speedo and gps seem to work just fine. Think of how often you are in reverse - mainly when reversing off a drive, or out of a car park. My system (Blaupunkt DXR70) must assume I'm in forward gear - which 99.9% of the time I am. If I am in reverse, its to get out of a parking space, and I don't need gps for that!
HTH
neil
Quote from: "GSB"down to about 2 feet in the right circumstances.
Blimey, you must visit some small places if you need to be that accurate s;-) ;-) s;-)
Quote from: "GSB"It also uses a reverse light signal, which in conjunction with the compass, allows to tell when your turning around. Sat Nav systems without this tend to take a short while to work out whats going on when you do that. s:shock: :shock: s:shock:
Doesn't make much difference really ... by the time I have turned, checked the traffic and ready to start paying attention again, the one I have is pretty well done with it's re-routing calculations ... the fact that it's only any good if you know where you're going is neither here nor there I suppose (sorry about that shocking pun).
Quote from: "GSB"I need a 12v signal from the reverse lights so it knows which direction its going. Anyone know if it appears in the wring loom around the dash anywhere? or do I have to run a wire from the switch on the gearbox or the light clusters?
These seem to be the choices:
1) The switch itself
2) Connector BD2, which is behind the left side storage bin removable quarter panel (IIRC, under one removable plastic cover). There are two connectors in there side by side, BD1 is closer to front of the car and BD2 closer to the back. Both connectors splice from the main loom that comes through the firewall. Pin7 is the one you want with R-L (red with blue stripe) wire.
3) The lights itself
(or cut into any wire between those)
Quote from: "Tem"2) Connector BD2, which is behind the left side storage bin removable quarter panel (IIRC, under one removable plastic cover). There are two connectors in there side by side, BD1 is closer to front of the car and BD2 closer to the back. Both connectors splice from the main loom that comes through the firewall. Pin7 is the one you want with R-L (red with blue stripe) wire.
Excellent info Tem, thats where I'll get my signal from... Thanks s:wink: :wink: s:wink:
Quote from: "aaronjb"I presume it must have a compass built in as well, as it seems to know what direction I'm facing even if I haven't moved anywhere yet (when I've just plugged it in)
nope, a gps unit works on line of site comms to a satellite constallation, it has a database of known satellite positions and using triangulation it works out your precise position and direction
i.e. if satellite 1 is on your left and is suddenly on your right then you must have turn around, so no, no compasses. Position is worked on basic triangulation based on 3 points but preferably more satellites are required for acuraccy. Of course it's a bit more complicated than that but thats the basics
Quote from: "aaronjb"I presume it must have a compass built in as well, as it seems to know what direction I'm facing even if I haven't moved anywhere yet (when I've just plugged it in)
nope, a gps unit works on line of site comms to a satellite constallation, it has a database of known satellite positions and using triangulation it works out your precise position and direction
i.e. if satellite 1 is on your left and is suddenly on your right then you must have turn around, so no, no compasses. Position is worked on basic triangulation based on 3 points but preferably more satellites are required for acuraccy. Of course it's a bit more complicated than that but thats the basics