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back to article Spanish boffins increase GPS accuracy by 90%

Boffins at Madrid's Carlos III University have used cheap accelerometers and gyroscopes - and expensive mathematics - to improve the accuracy of GPS* by as much as 90 per cent. The team compared their results to differential GPS - which is about as good as satellite systems get - and found that with detailed analysis of the data …

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Boffin

GPS for Dummies

Do we really need an explanation of what GPS is... in an article in The Register?

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Boffin

Re: GPS for Dummies

There is no harm in it. Those that don't know how it works benefit from it and learn something. Those that do know how it works ignore it or come to the comments section to make sure everyone knows that they know, ya know?

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Anonymous Coward

Re: GPS for Dummies

"Do we really need an explanation of what GPS is... in an article in The Register?"

As a brainbox on GPS, then, you can help me out with a little conundrum. If the cheapy GPS receivers in a mobile phone are only accurate to 10m, how does it (usually reliably) know which lane I'm in, given that would require circa 1-2m accuracy to give lane guidance to an acceptable degree?

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Boffin

Re: GPS for Dummies

Perhaps it's for Stephen Fry...?

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Re: GPS for Dummies

You do when you get statements like:

"The team compared their results to differential GPS - which is about as good as satellite systems get "

RTK can get the GPS accuracy down to sub-decimeter (less than 10cm).

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Re: GPS for Dummies

Because the normal accuracy is usually around 1-2 meters in decent conditions. However 10 meter inaccuracies are not unusual and are dependent on how many satellites are in view and whereabouts in the sky they are. There are other factors too, such as ionospheric and tropospheric error and even if the satellite is in the right place and broadcasting the correct time.

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Anonymous Coward

Re: GPS for Dummies

You do know that Stephen Fry is a gadget head? he has about 4 smartphones, one from each platform.

He had one of the first Apple Macs in the UK too, along with Douglas Adams.

I'm sure he's perfectly aware of what GPS is.

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FAIL

Re: GPS for Dummies

You might be sure, but you'd be wrong: "You send a signal from your GPS device..." http://www.theregister.co.uk/2011/01/18/stephen_frytard/

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Re: GPS for Dummies

Look on YouTube for Stephen Fry explaining GPS on QI, I think you will find he doesn't.

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Vic
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Re: GPS for Dummies

> I'm sure he's perfectly aware of what GPS is.

...But no idea how it works :-(

Vic.

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Silver badge

Re: GPS for Dummies

Sub-decimeter sounds so much more impressive than "a bit less than four inches", doesn't it?

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Silver badge

Re: GPS for Dummies

I think it is rather important to differentiate between a satnav device vs a GPS. I teach a ground navigation class once a year a semester at the local uni and I have to explain that while a satnav (generally) uses the GPS system to give directions, a standalone GPS only gives you your current location (unless data has already been put ino the system) and records your current location/path.

It is an important distinction. If I gave most people my Trimble GPS they would have a hard time getting from point A to B.

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Anonymous Coward

Re: GPS for Dummies

It presumes you're going in the right direction on the correct road and works it out using last know speed. Easy to test, hook onto a slip road you not supposed to do, then see how long it takes to notice that you are not where you are supposed to be. You could slam on the brakes and do a u-turn and again see how accurate it is, but probably not the best on the M1.

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Re: GPS for Dummies

direction of travel usually. calculated by sampling a preset duration of position previous to determine velocity

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Joke

Re: GPS for Dummies

>>Sub-decimeter sounds so much more impressive than "a bit less than four inches", doesn't it?

I bet you say that to all the girls!

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Anonymous Coward

Re: GPS for Dummies

Indeed it is important to distinguish between a satellite navigation system and "a GPS", which is a set of satellites orbiting the Earth plus the associated ground-based infrastructure.

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Boffin

Re: GPS for Dummies

"If the cheapy GPS receivers in a mobile phone are only accurate to 10m, how does it (usually reliably) know which lane I'm in"

Sorry, which GPS is actually giving you an indication of which *lane* you're in? It might know "northbound" vs "southbound" or similar (which is carriageway information, not lane) but it knows that purely from your actual direction. Sat navs "snap-to" roads, allowing them to be very accurate. Try coming off a road onto a farm track and watch it lose its way quite quickly.

Even when not snapping-to a known location where it expects you to be (roads), it can use fuzzy logic to determine where you are, as the 10m accuracy will vary over time, and a GPS knows that you'll roughly travel quite consistently. If your reading jumps from 5m side to side, it's more likely the error has varied rather than you've moved erratically.

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Re: GPS for Dummies

Sorry, which GPS is actually giving you an indication of which *lane* you're in? It might know "northbound" vs "southbound" or similar (which is carriageway information, not lane) but it knows that purely from your actual direction. Sat navs "snap-to" roads, allowing them to be very accurate. Try coming off a road onto a farm track and watch it lose its way quite quickly.

Even better, if it tells you to take a slip road off the motorway, and you don't, it'll take quite a while to figure out. It assumes that you are following it's instructions until you exceed the "snap-to" failure threshold. Normally it takes my car until I pass the roundabout at the end of the slip road before it figures out that I've ignored it's advice because near to home I know the roads better than it does (most sat-navs don't figure traffic lights into time calculations, so while the way it sends me is shorter, it takes longer because of the stop-start traffic. So I go the long way because there are no traffic lights. Usually get home sooner)

Of course, if you wanted to get real accuracy you'd use the encrypted GPS signal only (officially) available to the military. I forget what the accuracy is, but it's sub 1 metre from memory.

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Vic
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Re: GPS for Dummies

> which GPS is actually giving you an indication of which *lane* you're in?

Not quite a *lane* as such...

I use a bike computer[1] to track my flights. It doesn't snap to anything, because it's expecting you to be off-road (which is why it's useful).

It shows the track of my landings in a remarkably similar place to where I did them. Now the runway is wider[2] than a motorway lane, for sure, but the accuracy still appears to be somewhere near enough to discriminate between lanes...

Vic.

[1] It's an Android app called "Move!". I've found it invaluable for keeping a record of where I went and what I did.

[2] I can't find a reference to how wide it is - I'll ask on Sunday when I'm next there.

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Silver badge

Re: GPS for Dummies

I'd just be happy if the damn things gave me an indication of what direction they think I should take on the roundabout at the top of a slip road before I get to the ****ing roundabout itself.

I've made more navigational mistakes following sat navs than not. They're very useful but I also like to know where I'm going without them.

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Anonymous Coward

You do understand that an autonomous car wouldn't rely on GPS for general safety and moving about the road right?

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Beat me to it- you'd never be able to do it solely off GPS, as unnotified roadworks, obstacles in the road and (snigger) apple maps would mean that knowing where you are on the planet would only get you so far with where on the road you should be.

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Anonymous Coward

You do understand that an autonomous car wouldn't rely on GPS......

Really, I never knew that!

I thought GPS could spot pedestrians walking in the road, avoid ad-hoc road works and alert me to when a red light was on a traffic light.

Thanks for enlightening me.

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Terminator

Re: You do understand that an autonomous car wouldn't rely on GPS......

@AC 14:47

No, that's the satellite directly to the left. The one with "skynot" or something written on the side, can't make it out from down here.

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WTF?

Re: You do understand that an autonomous car wouldn't rely on GPS......

@AC 14:47 GMT

No, all those functions are handled by RFID. At least that's what the IBM RFID adverts were implying anyway.

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Stop

So

does the 2 metre accuracy mean it stops just before or just after the STOP sign??

;-)

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Facepalm

Re: So

As the author ought to know, close stuff is done by computer vision and lidar and such goodies.

Even if the maps were perfect and the GPS nanometer-good, you need to check the groundtruth before driving over it. Silly Bill Ray.

This accuracy is great for lanes, mind.

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Paris Hilton

Re: So

If it stops at all it'll be better than some drivers.

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Just skimmed the paper

It looks like they are using a Novatel OEMV which in the configurations I'm familiar with will run you about $6000. An IMU on the from crossbow similar to the one they describe is another $6000. I guess it is better than the $100K systems that some reaserchers strap on their systems but not cheap.

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Trollface

So you're still driving on the wrong side of the road?

'two meters to the left' wouldn't endanger pedestrians in most countries - only the passengers of the vehicle drifting to the left and those in the oncoming trafic. Two meters to the right, though, would be a different problem.

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Re: So you're still driving on the wrong side of the road?

Here's the generic formula for you:

2 metres to the left/right* = killing pedestrians/colliding with oncoming traffic*

* Delete as applicable

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Anonymous Coward

dead reckoning brought up to date then.

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Bronze badge
Boffin

It's inertial navigation. Nothing new really.

I've actually been wondering when car GPSes would start using inertial corrections to improve accuracy. It makes installation a little more complicated, since you have to put the accelerometers and gyros in the right place (likely slightly different for each car), but it would be a great factory feature.

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Gold badge

The one built into my car already does it.

It knows how fast its going (speed sensor) and which direction it's going in (steering angle sensor)[1], both of which are standard on most cars these days. Given a recent fix to start from, what else do you need?

It's always amusing to watch it trying to match the maneuvers I'm making in an underground car park to the roads above....

[1] Ok, most of the time. Presumably it wouldn't have a clue what was going on if I were to four-wheel drift it round a corner.....

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Vic
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It's always amusing to watch it trying to match the maneuvers I'm making in an underground car park to the roads above.

You want to see the confusion when you run one in an aircraft :-)

Vic.

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Bronze badge

Some Tomtoms already have this, and Android phones.

On Android it's next to the GPS on/off, called 'Use sensor aiding'. (Not sure if this is OS version or phone type dependent, but it's there on a S3).

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Bronze badge

I'd always assumed that smartphones already did this, as they have the sensors.

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Silver badge

The navigation system offered in the mid 90's by Fujitsu Ten under the Eclipse brand used accelerometers and gyros that had to be installed with the rest of the system (display, "magic box", cellular antenna and CD player where you put the map disc you wanted to use). It was complicated as hell, didn't work worth a shit, very expensive and sounded like a "speak and spell" when it spoke.

I don't think aftermarket sensors are ever going to be truly road worthy. The real advances will come when most/all OEMs offer more accurate systems from the factory.

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Gold badge

"The one built into my car already does it....

It's always amusing to watch it trying to match the maneuvers I'm making in an underground car park to the roads above....

Yeah, the one in my TomTom does it too, but only using a built-in accelerometer.

However sometimes I have to drive into Madrid city, where they have quite a long section of motorway underground, complete with junctions. The TomTom guides you into it, and then half-way through it suddenly decides that you are on the surface, and starts trying to snap your location to the roads up there. Meanwhile, it forgets to tell you which junction you were supposed to take to get out of the tunnels in the right place.

For me issues like that, and closed/new junctions on the 2nd busiest motorway in Madrid not being updated for >2 years is more of an issue than the inherant location accuracy.

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Also on the S2

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Anonymous Coward

Self driving cars will ultimately fail.

What is the point when the human will have to sit there and be sober and conscious?

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Anonymous Coward

You can kill time by Googling for impossible results?

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Anonymous Coward

Ultimately, you wouldn't need to be sober or conscious.

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Bronze badge
Go

Bring it on!

I can't wait for an autonomous car which can drive me home after I've had a few beers. We could also change from being a two-car family to being a one-car family: after the car takes me to work in the morning, it can drive itself back home then take the missus and spawn to their destination.

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Silver badge

Re: Bring it on!

That's my dream too. Just because I can drive, doesn't mean that I either like it or want to do it.

Unfortunately I think such true motoring convenience is at least a couple of decades away.

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Anonymous Coward

Re: Bring it on!

We already have them they're called buses, trains and taxis.

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Coffee/keyboard

Re: Bring it on!

No they're not. The nearest bus stop is 3/4mi away. Taking that to the train station takes over an hour.

Unfotunately, in the greater Atlanta area, we have several independent transit authorities and I think they're all run by either 1) idiots and/or 2) crooks.

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Las Carreteras

On the roads over here it's normal practice for drivers to have a standard deviation of 2 metres anyway. Roundabouts are a free-for-all.

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Pirate

Re: Las Carreteras

Sideways is +/- 2 metres. Forwards/backwards while on the move is precise down to a range of approximately +/- 25cm. Parking is precise down to the nanometre (don't worry, bumpers and number plates are designed to crunch).

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Re: Las Carreteras

'tis true. I'd say literally every single car has parking-related damage of some description.

Although narrow streets densely packed with cars have certainly improved my parallel parking skills (without using the bumpers)

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