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GPS in tunnels

2K views 13 replies 10 participants last post by  pidjones 
#1 ·
I always thought that the GPS signal would go completely away in a tunnel, but Sunday coming through the Cumberland Gap tunnel I noticed that Karen was keeping track of our progress perfectly, and never reported signal loss. Do they have GPS signal repeaters in tunnels now?
 
#2 ·
Not sure, but anytime I go through one of the local tunnels my GPS loses the signal. Granted, all the local tunnels to me go underwater and I'm sure that has something to do with it as well. While riding through some tunnels in the mountains I don't recall losing a signal, but its been a couple months since then and my memory isn't always the greatest.
 
#3 ·
Some GPS's use what's called Dead reckoning. It's a system that uses a known position, and based on the last known heading and speed, can compute within a certain accuracy your current position. This only lasts for a few minutes at best until the GPS starts loosing it's accuracy.
 
#4 ·
Pid,

We had a secret meeting with "Karen" and told her that the board could not afford to loose you. So, now you know the rest of the story!:agree: :coffee1:

Mike
 
#5 ·
Pid,

We had a secret meeting with "Karen" and told her that the board could not afford to loose you. So, now you know the rest of the story!:agree: :coffee1:

Mike
Well, I have become a bit confused in the tunnel. I guess I could get lost in it!:confused:
 
#6 ·
Do they have GPS signal repeaters in tunnels now?
GPS functionality is based on clear sight to the Satellites, passive repeaters will upset the timing relationship. WAAS support, if turned on, is a land-based GPS enhancement where the timing relationship is maintained. You may very well be receiving a WAAS signal to maintain lock.
 
#7 ·
My Zumo 660 will continue in a straight line for 30 seconds after losing signal. If the lost signal exceeds that it gives me the lost signal indicator. If it picks up a signal again within the 30 seconds I don't even know it was lost (unless the road turns and the icon doesn't).
 
#8 ·
Yet, that exact same unit would loose its signal while going north on the Blue Ridge Parkway with no ryme nor reason to the amount of foliage or rock formations, later that same day, coming south, it maintained its signal the entire length........go figure
That's because the hillbillies don't need no stinking GPS, so the Gubment didn't put satellites over that area. :lol:
 
#10 ·
I can't imagine wanting to check the GPS in a tunnel.
I usually know where I'm at before I enter a tunnel,or cross a bridge.

When in a tunnel or on a bridge I'm fully focused on the road,and trying to get through alive.
 
#11 ·
........For example, my 2610 stayed locked on, showing speed and location while traveling the whole way under Mobile Bay (I dont remember how long that tunnel is, but its underwater and took a couple of minutes to get through it) Yet, that exact same unit would loose its signal while going north on the Blue Ridge Parkway with no ryme nor reason to the amount of foliage or rock formations, later that same day, coming south, it maintained its signal the entire length........go figure
This is a 2720, so I suspect a very similar unit to the 2610 in many ways. I also loose track on the BRP. Usually it is when I turn my video camera on, but I have lost it at other times up there as well.
 
#13 ·
In 2008 I was leaving downtown Boston heading south relying solely on my Garmin Zumo 550 to tell me how to go. I went into the big dig tunnel that has several different exits, it never lost signal and guided me all the way. I just assumed there were repeaters in the tunnel???
 
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