[v-drive]

All,

This came into my mind, one of these days when I was going to the Bangalore airport in a Meru Cab. People who are in bangalore, and who have been in a meru cab recently would have noticed a shrill voice reminding the driver the moment he crosses 90KMPH. "Please Slow Down" is what she says, and the driver taps on the screen and she goes quite for some time.

I was wondering, that now the GPS chips are quite cheap, so what stops the car manufacturers, at least the luxury ones, or the ones who retail cars at above 7-8 Lac, in using a GPS chip and a small app to display the correct speed, distance covered etc ? This will be totally accurate, and there would be no speedo error, or the error because of upsizing or using a wrong tyre size.
Extension to this would be providing complete navigation in the car, but as we all know, the money there is for the maps, and not the GPS chip.

Just wanted to understand the perspective and opinion of the experts here regarding this.

Mods, i couldn't find a similar thread, if it exists, please merge.

[thedreamcatcher]

What is the value that a feature like this would add

Plus, the cost of putting this device in cars will take up the value marginally and will not be of use to a majority of people.

This is useful in cabs as their speeds not be moderated and regulated. To an extent

However, for those who want to, GPS devices like VX140 shows the vehicle speed also in the form of an ODO or a digital meter and also has a speed alert setting, which is pretty accurate. With my car it is marginally off at times by around 5 KM, else works perfectly

[CPH]

Reliability is a problem.

In tunnels and underpasses or places like New York, where the signal is weak if existent at all.

Many places in the mountains suffer from signal problems.

[freewheelburnin]

The simple reason why a G.P.S cannot be relied upon for speed calculation is that GPS devices need direct visibility with a minimum number of satellites to operate.What would happen if you are inside a tunnel, a parking lot,a dense jungle where trees obstruct visibility or for that matter any obstruction is there to the signal?But on the other hand a GPS could be used to calibrate the meters periodically.This could be a patentable idea

[formel_eins]

GPS can be good for navigation but for odo calculations and speed it is better left to present system.

Cons:
- GPS chips have a start up time, which is called time to fix. This could take anywhere between 40 sec-2 minutes. So all the distance travelled in this time would be lost
- Accuracy also relies on number of satellites which are visible to GPS chip. In cities reflection of coordinates occurs due to buildings, trees
- GPS signals are also very weak so in places like underpasses, underground parkings it wont work
- GPS also gets affected in cloudy, rainy weather.

Instead this technology could be used as a backup security system to locate stolen vehicles, immobilize them remotely, monitor your vehicle. Actually I work for such systems

[pranavt]

Because the moment your car went into a tunnel and came out the other side, it'd tell you that you were doing supersonic speeds and report your car to the nearest Police Car which would stop you and ticket you for doing unmentionable speeds. That's why!

[ph03n!x]

Most new phones come with accelerometer - they are not reliant on GPS, or are they? Can they be used to sense the absolute rate of motion? If yes, can't a similar implementation replace the speedo of cars? Am sure that with volume the prices can be brought down...

[pranavt]

Originally Posted by ph03n!x

Most new phones come with accelerometer - they are not reliant on GPS, or are they? Can they be used to sense the absolute rate of motion? If yes, can't a similar implementation replace the speedo of cars? Am sure that with volume the prices can be brought down...

Pretty sure accelererometers only measure relative motion and acceleration. And they are not reliant on GPS.

[freewheelburnin]

An accelerometer cannot pin point absolute position.All it can do is detect relative change in direction,absolute speed and relative change in position(Triple integral of acceleration).Now if you lose your G.P.S signal , the device can switch to accelerometers to use your relative position and direction with the stored previous absolute position(from G.P.S) to find your way.I am not sure whether a software exists that can handle this.But it is very much possible on an iphone.If the accuracy of the accelerometer is good then you could continue for several kilometers using this method.

Originally Posted by ph03n!x

Most new phones come with accelerometer - they are not reliant on GPS, or are they? Can they be used to sense the absolute rate of motion? If yes, can't a similar implementation replace the speedo of cars? Am sure that with volume the prices can be brought down...

[ph03n!x]

Umm.. we are talking about having an alternate solution instead of speedometers and odometers. So an implementation of accelerometer can do that, yes?!

Of course having them for GPS sounds dumb, even to me

[rajb3125]

If i am correct there was a project related to this in news sometime ago. I am not sure but i think an Australian Student did this for university.

But there are quite few bugs in the system which are not easy to correct:-

Line of Sight - As mentioned, Global Positioning System needs direct line of Sight to CLEAR SKY, just a small cloud can also affect performance.

Signal Performance - Most of the consumer GPS systems available come without DGPS and WAAS recievers and rely solely on RTCM data. Which is very slow and there is the biggest bottle neck. As one includes DGPS and WAAS reciever, well the price start to rise too.

Cold Startup times - Cold startup times is a big issue for GPS receivers, A car is expected to tell the speed the moment car starts rolling, no one will expected waiting 2-20mins for Signal capture (20mins is an extreme example during bad weather).

There are other issue with implementing GPS as a speedometer but i have listed major flaws which can be corrected but will cost fair bit to end consumers.

Cheers

[v-drive]

Hmm,
Various view points, and all of them make sense. But few years ago, GPS was a military application, and if we go few years before that, then the whole concept of pinpointing one's location anywhere in the world using a small device was as alien as what we are talking about now.

Why not, have a combination of a traditional speedo, and a GPS device. As I had said in my original email, luxury cars, or above a certain price points can have this as one of the features. It will also add to the safety of the car, as you can always locate the car when ever its driven in an open place, if its stolen.

So, the car starts off on a traditional speedo, once it gets the lock on to the satellite, then the GPS takes over, and they manage it amongst themselves.

Now, who was talking about a patentable idea ?? :-)

[deep_bang]

Originally Posted by v-drive

Hmm,

Why not, have a combination of a traditional speedo, and a GPS device. As I had said in my original email, luxury cars, or above a certain price points can have this as one of the features. It will also add to the safety of the car, as you can always locate the car when ever its driven in an open place, if its stolen.

GPS transmission is one way - the GPS device can only "know" the coordinates of where it is. In case of a stolen vehicle situation, this position would have to be transmitted to some other place. There is a solution existing which has a GSM SIM card attachment, which sends back the GPS data over GPRS. Now - i am not talking about some hi-fi solution on discovery channel, but a solution that is available as a product to buy.

I distinctly remember a stolen Scorpio was recovered in less than a day as he had fitted his vehicle with this mechanism.

[DerAlte]

Errr.... all that is fine, but what about the times when GPS / cellphone signal is not present? Basement, tunnels, tree cover, too many buildings (interference)? I think any and every car manufacturer will stick to things that are fool-proof, fail-safe and basic, just so that a non-geek end-user does not have the system failing for reasons not associated with the car.

Anyhow, components are available freely for anyone to conceive and assemble a system to one's needs.

[Thad E Ginathom]

... a solution that is available as a product to buy.

Such a solution has been available in my mother country for a long time (decades, I think). I think this was a homing device that guided police to the vehicle, but that was in the days before GPS was commonly available; maybe they've updated now.

The device was installed in the vehicle in a secret position that was not even told to the owner.

Affordable is relative, of course --- but to the purchaser of a brand new car, especially a luxury model, it would be a fairly nominal marginal addition. In a country where vehicle theft is common, it probably gives discounts on the insurance too.