View Full Version : GPS This astonished me.
Loose rivets
24th Jan 2009, 20:40
Just reading through to see the differences between the Sony 83t and the 94t and I read this:
The first feature demonstrated was the Position Plus technology which uses a gyroscope, an accelerometer, and (interestingly) a barometer to keep track of vehicle position to continue navigation when satellite reception is lost. We chose San Francisco's Stockton Street Tunnel as our destination, which is approximately three blocks long, and set off. Partway through the tunnel, we lost satellite reception, indicated by the display's position triangle turning orange, but the U94T seemed to keep track of our position.
Can this be true?...the report seems unequivocal.
Has anyone had experience of this model range?
green granite
24th Jan 2009, 21:00
Can this be true?...the report seems unequivocal.
Why not? it's just basic inertial nav stuff.
Loose rivets
24th Jan 2009, 21:03
Yes, but in my day anything with a gyro inside weighed over ten pounds and was labeled, "Handle like Eggs!"
Conan The Barber
24th Jan 2009, 22:06
It's probably a solid state 'gyroscope'. The technology has been around for a while.
iPhones and others have such sensors. Turn your iPhone on its side, and it will rotate the display between portrait and landscape. Lots of games use them. Why not combine them with the nav kit, since they are there.
MacBoero
24th Jan 2009, 23:21
Well close, but the iPhone and iPod don't have gyroscopes, but three axis tilt sensors. So the iPhone cannot measure or detect linear displacement, other than by using GPS position fixes, or mobile network triangulation.
It would be possible though to have something that small, and example of which developed in Devon found its way into the Segway...
http://www.siliconsensing.com/media/image/8/9/CRS03-pencil_thumb_1.jpg
Silicon Sensing - HOME (http://www.siliconsensing.com/)
BombayDuck
25th Jan 2009, 01:01
Yep, I've used them before and I'm studying them now. The chips are a nail's area and we've used a package to control a micro aircraft in flight.
Interesting that it has a barometer though; I think that is overkill for a car GPS. Or I suppose it may be useful while going up and down through hilly places as GPS is very notorious in vertical placements...
We used products by a company called 'Microstrain' - their site used to be very buggy though. Lots of 404 errors. Nice kit though, gave a good response up to 70 Hz query.
HuntandFish
26th Jan 2009, 14:58
Yep all sounds feasible .
R/C model helis rely on Gyros to hold the tail at a given heading
fireflybob
26th Jan 2009, 15:52
Interesting interview on the local radio station recently with a Professor in GPS! (Nottm Uni I think). Asked for predictions he said position information would still be available in underground car parks (eg) and then system would take you to aisle and shelf where your chosen product was in shop (which, of course, you have already pre-ordered via the system!). I guess this technology will use some sort of IRS when GPS signal lost.
Think these were the links:-
Professor of SatNav (http://www.bbc.co.uk/nottingham/content/articles/2009/01/15/professor_of_sat_nav_feature.shtml)
GPS (http://research.nottingham.ac.uk/NewsReviews/ExpertiseResults.aspx?id=4602)
More (http://www.grcnz.com/terry.aspx)
Loose rivets
26th Jan 2009, 17:12
That's interesting. As one who was on the electronics workbench about the time we got TWO transistors in one encapsulation, all this technology makes me believe in alien intervention! INS in the first DC10s was such an expensive option, it represented a significant % of the total cost!
It would seem that an inertial mode unit would be the only contender then. Knocks the spots off anything that frequently goes dead in cities like NY or Chicago.