Thread: GPS for under £70.00

That look like a good GPS, cheap too. I keep thinking if its as good as garmin GPS16...probably better.

Can you keep a lock inside a tunnel?

dont know, I havent been to far in it yet, but there isnt any tunnels round here.. I wouldnt expect any to keep a lock in a tunnel

I use the USB version of this reciever under WinXP and with InfoMap Navigator and Route66, no problems at all. Luckily I have a sunroof on the Vectra so I have no problem with placement.

Going through tunnels will result in loss of satellite signals (duh!) but since the GPS reciever is warm and have a position that is (usually) very close to the one it gets upon exiting from the tunnel, this is no problem, it picks up the cars position almost instantaneously.

Under the roof of a gas station the other day I even picked up 4 satellites.

Going through tunnels will result in loss of satellite signals (duh!) who said that?

Thats not true m8, what receiver have you tried? you obviously never owned a decent one.

Im using garmin GPS16 and have tried it in rotherhite and blackwall tunnel in london, both are 3/4 - 1 mile long. The GPS can keep the lock with no problems, Although it looses the heading and position accuracy when I reach the middle of the tunnel but it carried on working. How do you explain that? If it did lose the signals it relock within seconds.

The reason why I asked because I used to use the SONY (ETAK GPS1) and losses lock once I pass slowly under a railway bridge thats only 10m wide or so, then another few minutes before it relock...what a piece of crap. Tried TomTom bluetooth GPS and some other brand on my Ipaq PDA, not impressive at all.

Under the roof of a gas station the other day I even picked up 4 satellites
I get 7-9 on mine.


Garmin GPS16 cost about £130-150 against a £70 GPS. It may be good thats why I asked how well it peform and garmin is probably just over priced, ripping us off. Garmin GPS18 is out soon with the same spec as GPS16 I dont know how well it perform in real life though.


Check it out here :

http://www.gpscity.com/gps/brados/15.../oem18usb.html

Yes its only $84.95 = £45.64 even if you have to pay postage and taxes it is still cheap cosidering you have a better receiver. Exchange rate is good, so its best to buy in USD.

Sorry CdRsKuLL Im not trying to put down the fortuna, just trying to compare how well it perform against the others. Shame you dont have tunnel there to test it.

Whenever I buy a new GPS, first thing I do is drive through the 2 tunnels we have in here

Originally Posted by Ricky327

Whenever I buy a new GPS, first thing I do is drive through the 2 tunnels we have in here.

I find I rarely get lost in tunnels, although there is a maze forming under Boston now so who knows! I think any GPS would do well to get throught he big dig tunnels.

As a GPS needs a clear view of the skies I asssume anything that "works in a tunnel" is at best estimating, or just not giving up as fast as other GPS units? I don't see how it could actually work underground.

Chris.

Apparently theres a new supersensitive GPS :

http://www.eetuk.com/tech/news/dev/OEG20031128S0004

Theres another article about this new technology somewhere on the net...I cant find it again

I find I rarely get lost in tunnels, although there is a maze forming under Boston now so who knows! true

I got lost when I was under a tunnel in norway, with my crappy GPS as soon as a exit the tunnel it cant lock until I traveled a few miles. I do find it amazing how it can keep the lock under a tunnel...I had some experience where Im in the city with lots of building on a narrow road, I had problem with accuracy driving there.

Originally Posted by Ricky327

Going through tunnels will result in loss of satellite signals (duh!) who said that?

Thats not true m8, what receiver have you tried? you obviously never owned a decent one.

Im using garmin GPS16 and have tried it in rotherhite and blackwall tunnel in london, both are 3/4 - 1 mile long. The GPS can keep the lock with no problems, Although it looses the heading and position accuracy when I reach the middle of the tunnel but it carried on working. How do you explain that? If it did lose the signals it relock within seconds.

That's just not possible! GPS is line of sight. If it can't see the satellites it can't calculate the position.

Ok heres the science bit

Satellites are equipped with very precise clocks that keep accurate time to within three nanoseconds - that's 0.000000003, or three billionths, of a second. This precision timing is important because the receiver must determine exactly how long it takes for signals to travel from each GPS satellite and therefore the distance to the satellite. The receiver uses this information to calculate its position.

When you go into a tunnel you WILL lose the signal. The first thing you will lose is altitude. Most GPS can keep calculating the position using just 3 satellites, some can approximate it using 2. Speed is calculated as the distance travelled between 2 fixes.

Yes I know in theory it not supposed to work and I do believe the theory.

But from my experience with GPS16 it does work, I dont know why. I drove through the tunnel many times and still show the possiton correctly just maybe 5m off. On different day it sometimes looses the lock, but the point is it carried on working most of the time

I am indeed amazed why this is so.