Thread: GPS reception in tunnels

The problem is that GPS works by a very complicated algorithm which calculates using the constants of the speed of light and the time difference between satellites with known positions when the time signal is received by the receiver on the ground.

The only way to reproduce this would be to install multiple artificial satellites transmitting time signals throughout all the tunnels and have this data installed into every GPS receiver in the country. Then the accuracy of all these devices would have to be increased to better than that in surveying equipment because the time difference between artificial satellites in the roof of the tunnels will be so close as to render most devices useless.

The only way to get them to actually work in tunnels would be to have a second function in the GPS receiver that calculates speed, using signals emitted by transponders at fixed intervals along all tunnel ceilings. This function could activate when the GPS signal is lost as the vehicle enters a known tunnel.

You could always use the speedo!

when i visted syd (from adel) last year i used gps to get around syd. missed the turn off in the tunnel, stupid gps didnt know where i was.

GPS doesn't work underground for reason given above. You can't blame the device for a user who doesn't know the limitations of the equipment they are using. a saying about workmen and tools springs to mind.

to increase reception in my defender years ago i purchased an antenna that took signal from the roof and transferred to inside the car for better reception

drilling holes in our tunnels might cause some leaks

just figured with more and more tunnels coming online there would be a smart cookie out there inventing a simple solution

i cannot read my speedo, not enough back lighting when it gets dark......

Originally Posted by OffTrack

GPS doesn't work underground for reason given above. You can't blame the device for a user who doesn't know the limitations of the equipment they are using. a saying about workmen and tools springs to mind.

i couldn't remember which was the best exit to take on sat, when the GPS re-connected i discovered i should have taken the one prior....oh well

btw, i understand the limitation of the device in its current form but in this modern world i am sure there will be a solution some time in the future. just imagine if nobody thought outside the square

If Governments and tunnel owners worldwide could get together with manufacturers of GPS receivers I'm sure it could be solved. The real issue is that the GPS system was launched by the US military and there is no benefit to them to solve the civilian tunnel problem.

If transponders in tunnels could transmit their location rather than a time signal and GPS receivers had a function to calculate from it. There is no reason that speed and turn-by-turn navigation functions couldn't operate in tunnels.

It's just getting an agreement on an international standard and a committment from tunnel owners to install and maintain the equipment.

The in-built GPS in our 2010 Subaru Forester works in the Sydney M5 tunnel. I assumed it had some sort of inertial system to maintain track. It's accurate, too.

Originally Posted by p38arover

The in-built GPS in our 2010 Subaru Forester works in the Sydney M5 tunnel. I assumed it had some sort of inertial system to maintain track. It's accurate, too.

Well there you go, progress is being made