Naked Science Forum
Non Life Sciences => Technology => Topic started by: neilep on 24/06/2010 16:53:42
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Dearest Direction-ologists,
As a sheepy I of course know which direction I am pointing at all times. I have cute nose and a sexy bum which help me with orientation joyness !!
I also luff to drive…look here I am taking same time out in my run-about to go get some milk from the store 100 metres away.
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Me In A Car Buying Milk 100 Metres Away
Fortunately I have a thing called Sat Nav which is really useful as it helps me find the way. I think it uses echo location like what bats and dolphins use or something !..Anyway, should I decide to drive the whole way in Reverse would Sat Nav know this and keep asking me to turn around ? If it does know which way I am facing....then how does it know so ?
I need to know because there are times when I just can not be bothered to turn around !
Whajfink ?
Hugs and shmishes
Mwah mwah mwah !
Neil
Buyer Of Milk In A Veyron
xxxxxxxxxxxxxxxxxxxxxxxx
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Erm, well the Geezer brother supplied one for crimbo, but seeing as the Geezer brother lives in Aberdeen, he bought the cheapest one that Radio Shack had on offer.
I'm pretty sure it doesn't have the foggiest idea whether the vehicle is going forward, backward or even sidey-ways. It will only start to complain if it finds it is not following the route it calculated. Of course, it complains a lot if it finds out you are taking it in the opposite direction!
"Do a U-Turn at the first opportunity! (you flipping moron)"
(It doesn't actually say the last bit, but it definitely implies it.)
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It would not know, it just cares that you are moving, and along a road that is in it's internal map, and are reducing the distance between the starting point and the destination.
The car may suffer a lot of wear in the gearbox, as this gear is really meant for really short travel and not often use. As well you will find your fuel use will be similar to the QE2, around a gallon an inch.
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GPS and SatNav receivers can't tell which way you're facing/pointing. However, if you are moving, or have moved since the GPS was switched on, it'll know in which direction you're moveing/have moved.
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Thank ewe Geezer, SeanB and LeeE
I do appreciate very much your comments. Of course ewe're right...erhmm..that's not suggesting I already knew the answer, I did not,...but when I read how ewe have explained it, it's pretty darn obvious.
As a firm believer in empirical study though, I will set my Sat Nav tomorrow and drive the 100 metres in reverse along my street and will report here the proof of your wisdom.
Ta
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Thank ewe Geezer, SeanB and LeeE
I do appreciate very much your comments. Of course ewe're right...erhmm..that's not suggesting I already knew the answer, I did not,...but when I read how ewe have explained it, it's pretty darn obvious.
As a firm believer in empirical study though, I will set my Sat Nav tomorrow and drive the 100 metres in reverse along my street and will report here the proof of your wisdom.
Ta
If it's not built into the vehicle, you can get the same effect by turning it through 180 degrees rather than driving backwards.
Might be a bit safer too! You don't want to prang the Dodgy Ram.
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For something relying on GPS alone, you are all correct that there is no knowledge of vehicle direction. However that is not wholly the same for all "SatNav" systems which are often not just a simple GPS. I am not familiar with many designs but quite a few automotive devices have accelerometers built in so that you can track progress when no signal is present (in a tunnel for example). If you stop, or even reverse or turn along a fork, in a tunnel (for example) the system knows this. Some of the built-in units may be linked to the vehicle's systems - I'm not sure about this though. Anyone who has a boat with a chartplotter will also know that the Nav System is tied in to the magnetic compass too, as well as many other of the boat's systems (AIS, Radar etc).
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Thank ewe Geezer, SeanB and LeeE
I do appreciate very much your comments. Of course ewe're right...erhmm..that's not suggesting I already knew the answer, I did not,...but when I read how ewe have explained it, it's pretty darn obvious.
As a firm believer in empirical study though, I will set my Sat Nav tomorrow and drive the 100 metres in reverse along my street and will report here the proof of your wisdom.
Ta
If it's not built into the vehicle, you can get the same effect by turning it through 180 degrees rather than driving backwards.
Might be a bit safer too! You don't want to prang the Dodgy Ram.
Thanks Geezer, mine is built into the car but if someone wants to save me driving like an idiot for a while then please just flip yours through 180 degrees and conduct this vital experiment ! There's a paper in this I am sure !
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Thank ewe Geezer, SeanB and LeeE
I do appreciate very much your comments. Of course ewe're right...erhmm..that's not suggesting I already knew the answer, I did not,...but when I read how ewe have explained it, it's pretty darn obvious.
As a firm believer in empirical study though, I will set my Sat Nav tomorrow and drive the 100 metres in reverse along my street and will report here the proof of your wisdom.
Ta
If it's not built into the vehicle, you can get the same effect by turning it through 180 degrees rather than driving backwards.
Might be a bit safer too! You don't want to prang the Dodgy Ram.
Thanks Geezer, mine is built into the car but if someone wants to save me driving like an idiot for a while then please just flip yours through 180 degrees and conduct this vital experiment ! There's a paper in this I am sure !
Dear Sir,
At your request, I have conducted the experiment, and I am able to report that my el cheapo GPS doesn't seem to give a rats have any particular preference for orientation.
I will forward the complete report of the experiment to you on receipt of $200.
Your humble servant,
etc
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Thank ewe Geezer, SeanB and LeeE
I do appreciate very much your comments. Of course ewe're right...erhmm..that's not suggesting I already knew the answer, I did not,...but when I read how ewe have explained it, it's pretty darn obvious.
As a firm believer in empirical study though, I will set my Sat Nav tomorrow and drive the 100 metres in reverse along my street and will report here the proof of your wisdom.
Ta
If it's not built into the vehicle, you can get the same effect by turning it through 180 degrees rather than driving backwards.
Might be a bit safer too! You don't want to prang the Dodgy Ram.
Thanks Geezer, mine is built into the car but if someone wants to save me driving like an idiot for a while then please just flip yours through 180 degrees and conduct this vital experiment ! There's a paper in this I am sure !
Dear Sir,
At your request, I have conducted the experiment, and I am able to report that my el cheapo GPS doesn't seem to give a rats have any particular preference for orientation.
I will forward the complete report of the experiment to you on receipt of $200.
Your humble servant,
etc
With respect for all that is holy and may the lord shine upon thee..gawwd bless thee..
Dear friend,
I am sheepy....conductor of an experiment that ewe have carried out....I was entrusted with this experiment by a Mssrs Rosemary & Thyme..unfortunately they departed the Earth when during the consequence of an incredible set of events they were accidentally stuffed up a chickens arse with some bread crumbs. They have left the considerable sum of twenty trillion trillion £s for which I am the executor. Gawwd bless !
For me to release to ewe your request for $200 means ewe are eligible to receive 20% of the many trillions. Please deposit the sum of one million pounds (as an admin fee) and I will release to ewe the $200 plus 20% of a few trillion squid.
It is written in the book of Fraudulations that thy will be delivered into the kingdom of Dupe-nicity all those that conduct the experiment of thy lord Satus Nav-arse.
gawwd bless ye !
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Most built in GPS units use a much simpler method to do the reckoning when GPS signal is unreliable. There are generally 4 wheels on the vehicle that provide input as to distance traveled, and it is simple to calculate turning from looking at the rotation rates of any two wheels on an axle.
The only system that uses acceleration is aircraft navigation systems. The original 747 system used 3 gyro units and 3 accelarometers to provide input to the computers that gave positional information. The system is so accurate that it required compensation for the turning of the earth, the motion of the earth around the sun and the motion of the sun around the galaxy. You could fly around the globe and, providing you left it on all the time ( normally done, as it takes a long time to start up and become stable in reading) when you came back to your parking spot the error would only be a couple of metres.
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A random review:
http://www.pocketgpsworld.com/tomtom-go-930-review-a1042.php
"As you drive along you will often encounter places where the Satellite signal is blocked such as tunnels and underground parking lots. TomTom has introduced a system called EPT (Enhanced Position Technology) to keep track of your position using accelerometers. This is not as accurate as GPS but will help guide you in places like Boston where the Big Dig has created a network of underground roads."
Iphones have accelerometers in them for example. It's not such a big deal with MEMS technology though not as accurate as the inertial platforms used in air navigation systems. I think the "round the globe with two metres accuracy" seems a bit unlikely though, Sean. I suspect it may have happened once and has become a good story. These systems are very good but the small errors from each acceleration build and the position random walks away from the true route. Flying across the atlantic you would be lucky to be withib a few km of your predicted position without radio beacons or, now, gps.
You may be right about getting data from the in-car computer for some of the built-in systems but there is no such connections with the add-on variety.