BMW Sat Nav (GPS) - do you use it?

[AlanJ]

The BMW system uses the car motions to calculate the position, there won't be any GPS reception for that system either but at least the system moves and won't leave you guessing when you are in tunnels or near high buildings.

Uses an age old principle of navigation called 'dead reckoning' based on the last known speed, direction, and position. When the signal is lost the 'system' will continue to 'dead reckon' your position and providing there is no massive alteration in direction or variation in speed will continue to give you an approximate position until the next set of satellites are picked up when it will update fairly quickly. Not a function of cheaper systems but then in many instances such immediate 'update' positioning is not required. As for signal reception any building will reduce the potential for satellite lock either through a blind spot or signal reflection whatever the cost of the system.

However mostly when I am in a tunnel I am fairly certain where I am and the direction I am going anyway...... sorry pvr couldn't resist :roll:

 

[Dr Phibes]

My old TomTom Go 700 used to lose the signal regularly in London. I purchased the external antenna, and things improved very slightly. BMW system has not dropped the signal once yet even in the same areas of London, so that is one up for BMW over my old TomTom. My later TomTom Go 740 holds onto the signal much better than the older TomTom, but still on occasion loses it. On the odd occasion too, it point blank refuses to lock onto a signal at all from start up. I've had it switched on for 3 or 4 minutes without it locking in - Strange...
It has been very handy with the Map Share function though, where every time you connect it up to the PC, it will download user submitted changes to roads such as limited access / blocked roads etc. If you stumble across a road that you can for instance, no longer turn RIGHT into that road, you can alter the details in the TomTom, and these are then uploaded to their database for all other TomTom users to download. When I was in London a few weeks ago, the TomTom tried to send me the wrong way into a one way street TWICE as well as trying to get me to take a left turn into a NO LEFT TURN street. I later made the neccesary changes to these streets on my TomTom, then uploaded them to the main database. - A handy feature, but a bit naughty for TomTom to overlook these mapping errors in the first place - and before you ask, I have the latest maps installed on the device, so there is NO excuse.

As I said above, only negative I can see for the BMW system is that it needs to be more customisable (colours / POI's etc)

 

[pvr]

However mostly when I am in a tunnel I am fairly certain where I am and the direction I am going anyway...... sorry pvr couldn't resist :roll:

You have not driven in Switzerland where there are junctions INSIDE the tunnel

 

[AlanJ]

However mostly when I am in a tunnel I am fairly certain where I am and the direction I am going anyway...... sorry pvr couldn't resist :roll:

You have not driven in Switzerland where there are junctions INSIDE the tunnel

I stick by my original comment......

 

[peddy]

Hmm - are you saying that your Garmin has reception inside a tunnel? All the ones I have used don't know where they are when you go in a tunnel and the screen goes blank, so if the tunnel is a couple of miles like in Switzerland, you get lost.

The Garmin I rented in NY city, did NOT work around the high buildings either.

Generally, no GPS receiver will get a reception in a tunnel. The ones built into the car have an advantage as they can use an external antenna (though I don't know where the antenna for the GPS is in the Z4, I think I read it was in the boot in the duck tail?). Removable GPS's are therefore more susceptible to reception issues if you don't fit an external antenna. Placing them further up the windscreen will mean they may not get as good a view of the sky and harm reception. Still, in a concrete tunnel that's underground or through rock, you're not going to get a reception no-matter how good the antenna is

I've always found if I place them as far down the windscreen as possible that they get a good reception - some of the tomtom units have the antenna in the suction cup, which is fairly ideal for reception.

The Z4's Nav seems to get a fix quickly, but it's likely this is due to it starting up earlier than an external device. I think the computer is active as soon as you unlock the doors, so that time it takes you to walk across the remaining 20 metres of the car park, get in, get comfy, get the car started etc means the GPS has already done a warm fix and you're ready to rock.

Some of the GPS's guestimate when you're in tunnels. Tomtom certainly does, it's ability to continue to guestimate depends on how constant your speed is. Eventually it'll give up but it's certainly a decent effort if you maintain a continuous pace.

One of the big benefits of tomtom on the iPhone is that you buy it once and you get free map updates and software updates rather than having to pay to upgrade on the normal devices - I like this a lot and think it's an important consideration if you're looking for a new SatNav!

When there's no signal the satnav uses the abs sensor to predict where you're going, which is very accurate. So it'll work perfectly in non-signal areas such as tunnels, etc.

 

[AlanJ]

When there's no signal the satnav uses the abs sensor to predict where you're going, which is very accurate. So it'll work perfectly in non-signal areas such as tunnels, etc.

Alright when you travelling in a straight line but how does it predict changes in direction?

 

[cj10jeeper]

Alan - I posted above the basics of how the system works without satellite, but the last few posts seems to simply miss that

I've had a quick scan of the factory information and there's about 20 pages on the operation of the GPS system but there are some interesting things:

Firstly rear wheel ABS sensors input to the DVD module, so it knows forward distance and presumably left/right
Secondly forward and reverse is identified by, in manuals the reverse light and auto the selector lever, so it knows forward or rear travel
Thirdly from the internal diagnosis is reference to a 'gyro' Sadly it does not specify what this is and how it inputs information.

Abstract of input tests:

Sensor Check Wheel
835 RL Navi
835 RR Navi
Satellites 05
GPS Status Position Known
Gyro 2500
DIR Forward/Reverse


Telematics Abstract:

Sensor Check Wheel
Satellites
GPS Status
Gyro

Direction
ABS Sensors, pulses/minute, neg. when reversing
Number of satellites currently received 07:
3 Satellites received, position possible
11: 2D Position Determined
12: 3D Position Determined
+,-, 400: mV setpoint value, halted or driving straight
ahead, >right-hand, <left-hand curve
Reverse Signal Detection

One can therefore reasonably interpret that the systmem is pretty capable of functioning for a period without GPS signal

 

[Siftah]

Picking up on pvr's comment above the Zed uses the ABS system to calculate the actual and realative rotations of the wheels and from that can calculate accurately the position of the car without GPS at all. It then checks GPS and adjusts accordingly as and when it gets a signal. For this reason it works soooooo much better than any portable under difficult signal situations.

Ahh, that's interesting!

 

[Siftah]

You have not driven in Switzerland where there are junctions INSIDE the tunnel

Lots in Germany too and a couple of tunnels in Italy where you turn *right* after you exit the tunnel!

 

[MyNamesNotBob]

Mine's on pretty much all the time in map view even if not set to a route.
I leave the screen up all the time as it's great to see calls come in, cd selection & audio, on screen, and most importantly general maps of where I am.

When I do need to navigate it rarely let's me down (but did on the way to a Zed meet of all times...lol)

Same here, since getting mine a massive week ago I've had the screen up most of the time, but thats mainly for track listings and phone - although it was used on 4x 250mile trips this week, where after the swearing at it for not having a 5 year old street in and being unable to work with postcodes it worked as good as gold.

 

[aquazi]

i also have mine on nearly all the time... in split screen mode.... so atleast i know the road name if i have the radio or ipod on the main screen!

Also even when i know where i am going.. i often set it as it does have a pretty handy trafic update feature and warns of delays on the route so i could plan around if i need to (however i never let the nav reroute - or set it to "dynamic" as i find that useless!)

 

[Lucy]

I use mine when I don't know where I am going simple as that, frequency doesnt come into it.

x2 Took the words out of my mouth!

I like it. I don't really have any complaints with it apart from not being able to just put a postcode in, and even when you do get to the postcode bit you can't put the full one in. Apart from that though I think it's a pretty good bit of kit and comes in useful sometimes. The screen is also useful for things other than sat nav.

I'd definitley want it in my next car.

 

[neilrjones]

As OEM systems go (and I've played with a few) the Z4 is good.

My only issue is route calculation. The 'quickest' route option seems to constantly do it's best to get me to a motorway (or keep me on one for as long as possible) as its logic for a fast journey. This is regularly not the best case and my old (ancient) TomTom is far more "intelligent" in telling me where to go. Also, when I persist with the theoretically slower route, the Nav recalulates to show a short FASTER route than the motorway option!!

Anyone sharing these frustrations?