Sunday Times Review of GPS Systems

[izani]

Basic rules - GPS signal need line of sight from GPS geostationary satellite to the receiver. In tunnel - of course no signal. Hence GPS won't work. Lots of solution been implemented. But not in Garmin Nuvi at the moment.

this basic rule is of course known to us. All we are asking for is not for the gps to work even w/o satellites but not to leave us in the lurch e.g. Follow TomTom's solution of continuing the route in some sort of simulation mode. Or minimum just allow us to see which exit to take.

If like that, then use Tom Tom lah... better than Garmin Hopefully can work with forking tunnel

[aed]

in malaysia if there is product review it is normally the personel that review the product not an expert just normal people and always not comparing apple to apple but apple to durian..hehehe.. this include all review not just gps... car review, camera review...

for me i'm using my gps on my fishing trip, kayaking trip, bike trip, 4wd trip..and also normal driving daily....so the best for me is my 76csx....

[moeyhc]

The other way they are looking at is to make the alogrithm switch to a mathematical model simulating your speed and direction of travel once the antenna loose the connection to the satelites and guessing which exit in the tunnel you are suppose to exit...

Hmmmm .... this is interesting. How does a GPS who has lost its signals knows its own speed and direction of travel? It is only possible if the GPS is equipped with a Gyro and an Accelerometer.... this is how they travel in space... so it will definitely work on Earth....

[lost4ever]

Hmmmm .... this is interesting. How does a GPS who has lost its signals knows its own speed and direction of travel? It is only possible if the GPS is equipped with a Gyro and an Accelerometer.... this is how they travel in space... so it will definitely work on Earth....

And they call it Dead Reckoning ... bro Taipan was working on it when he was much younger.

[tks]

If like that, then use Tom Tom lah... better than Garmin Hopefully can work with forking tunnel

I would if not for the fact that in almost every other area including map availability, Garmin is much better. I am simplying pointing out this single area in which Garmin irritates me. Not tring to suggest that TomTom is better.

And yes, of course it works with forking tunnel. It will work even if there are 5 forks. Not sure if you don't understand what I am saying or whatever. But the TomTom solution which I am referring to is not actual GPS navigation. Basically, the system will not die on you but will continue to show you the route and exit you were supposed to take, so that you can at least navigate out of the tunnel. It's not sophisticated at all. Definitely Garmin can do something like that by just tweaking its software. Maybe that's what some of the guys here are trying to do.

If you have Garmin in a tunnel with forking inside the tunnel, you are dead. Unless you had prior knowledge which fork to take.

[KC*]

I think dead reckoning will be a standard feature within just a few years.

However, there are other ways positioning can be assisted.

Incidentally, there are ways positional signal can be replicated by transmitters within tunnels. I suspect this was the case when I was driving thru a tunnel north of Barcelona earlier this year. Tunnel cut thru mountain but I had FULL signal on my Nuvi for the entire duration of more than 10 min.

[SOSweet]

I think dead reckoning will be a standard feature within just a few years.
However, there are other ways positioning can be assisted.
Incidentally, there are ways positional signal can be replicated by transmitters within tunnels. I suspect this was the case when I was driving thru a tunnel north of Barcelona earlier this year. Tunnel cut thru mountain but I had FULL signal on my Nuvi for the entire duration of more than 10 min.

Just like the H/P reception.

[lost4ever]

I think dead reckoning will be a standard feature within just a few years.

However, there are other ways positioning can be assisted.

Incidentally, there are ways positional signal can be replicated by transmitters within tunnels. I suspect this was the case when I was driving thru a tunnel north of Barcelona earlier this year. Tunnel cut thru mountain but I had FULL signal on my Nuvi for the entire duration of more than 10 min.

Stumbled on this site which talks about the re-transmission of GPS signals.

That's interesting, KC. Can you remember which tunnel specifically? May be heading to Barcelona in a month or so.

[tks]

Looks like the Nuvi 755T now has something like the TomTom feature that I was talking about, but I am not sure. The device continued to work by assuming some average speed and did not stop working completely, as is the case presently. Need someone with 755T to verify.

I have come to love these lane assist features. Totally saves you when you are approaching a difficult turn situation. Garmin isn't the first to the game with this feature, but it's welcome nonetheless. I seem to see the Lane Assist pop up on many intersections that are anything more than just a normal off-ramp, which I admit is a big help. It appears to be limited to highways/limited access roads at this point. The image below was from my trip to Logan Airport - and yes, I am in the Ted Williams harbor tunnel when this popped up. The Nuvi 755T assumes some average speed when navigating through the tunnel, and still offered this Lane Assist help as I was approaching the Logan Airport ramp. Well done.

http://www.gpslodge.com/archives/021869.php

[shoemaker676]

i have the same experience when driving in Japan, from Narita to Tohoku. The on board GPS are able to guide me tru all the tunnel without any reception issue. my 60csx however gave me the dreaded lost signal prompt 20 to 30 meter in tunnel. It amaze me how they are able to channel the signal into the tunnel, some of them are a few km long.....