Issue with route given by GPS

Moderators: Chuah, Moderators, Regional Mappers

User avatar
silverbeauty
Moderator
Posts: 3526
Joined: Tue Sep 16, 2008 6:29 pm
Location: Sin-Ka-Pu-Ra Garmin Nüvi1350, 3790T, Fenix, eTrex HcX Panasonic ICE+Garmin Samsung Note3 Apple iPad3

Re: Issue with route given by GPS

Postby silverbeauty » Fri May 20, 2011 10:41 am

DPBaker wrote:While I was in the tunnel I changed speed from 80km/h to 60km/h and the GPS changed speed to reflect my actual speed. Unless there is some sort of accelerometer in the GPS I can't really see how it would do that without some sort of external transmission. My GPS is a Garmin 1460.


GPS does not loose satellite signal immediately ... you can go quite a distance before it does ...

DPBaker
Posts: 15
Joined: Sun Jul 19, 2009 6:02 pm
Location: KL

Re: Issue with route given by GPS

Postby DPBaker » Fri May 20, 2011 10:48 am

Yes, I go through the tunnel at The Curve a few times a week as well as the one near Genting, so am pretty used to how long the GPS goes before losing lock - usually just before the end of the tunnel. But one tunnel I was driving through in Singapore is at least 5 times as long and it didn't lose lock at all. Also the speed changes wouldn't occur if it was just dead reckoning.

User avatar
gpsnerd
Contributor
Posts: 1410
Joined: Fri Jun 12, 2009 10:49 pm
Location: SG, MY

Re: Issue with route given by GPS

Postby gpsnerd » Fri May 20, 2011 11:34 am

maybe its better to view the route rundown before u proceed to make sure u are guided on the right track
User of 205 / 205W
Currently using 255W and 205W, 4592 LM

User avatar
vash_h
Posts: 428
Joined: Fri Oct 10, 2008 12:14 am
Location: Petaling Jaya
Contact:

Re: Issue with route given by GPS

Postby vash_h » Fri May 20, 2011 6:42 pm

if not mistaken, i read somewhere that singapore installed repeaters in their tunnels so you can continue to use ur gps navigation, cell phones in tunnels..
<-My Blog: HaroldChia.com->
<-MFM MAPS + Garmin Nuvi 50LM + Papago Z1 + Garmin Nuvi 205w + Samsung Galaxy Note 2 N7100 ->

DPBaker
Posts: 15
Joined: Sun Jul 19, 2009 6:02 pm
Location: KL

Re: Issue with route given by GPS

Postby DPBaker » Fri May 20, 2011 6:54 pm

vash_h wrote:if not mistaken, i read somewhere that singapore installed repeaters in their tunnels so you can continue to use ur gps navigation, cell phones in tunnels..

I suspect that too, but can't figure out how that would work - if you had a fixed antenna outside the tunnel then just re-radiated it, all the gps units inside the tunnel would show the position of the receiving antenna outside the tunnel. It must be a more technical setup than just re-radiating. I am just inquisitive and like to know how things work! :-)

User avatar
EastMushu
Valued Contributor
Posts: 201
Joined: Wed Sep 17, 2008 2:17 pm
Location: Bukit Batok (Nuvi 3790v)

Re: Issue with route given by GPS

Postby EastMushu » Sun May 22, 2011 8:28 pm

Cell phone repeater yes but doubt so for gps though as have travelled KPE a few times and signal will be lost before the car exits the tunnel...

User avatar
Redstorm
Contributor
Posts: 211
Joined: Tue Sep 16, 2008 4:30 pm
Location: Singapore

Re: Issue with route given by GPS

Postby Redstorm » Sun May 22, 2011 10:10 pm

EastMushu wrote:Cell phone repeater yes but doubt so for gps though as have travelled KPE a few times and signal will be lost before the car exits the tunnel...


It is not any kind of repeaters used inside our outside the tunnels. Only when using either Garmin CN or MSM maps, the device will go into simulation mode once it lose signal inside the tunnel, provided the vehicle travels at a constant speed from the time it enters and exit the tunnel. Fluctuation in speed inside the tunnel should not be a lot otherwise the simulation mode will not work. What they actually did is some coding on the maps to get the simulation to work when it loses signal.
Free beer tomorrow!ImageImage

DPBaker
Posts: 15
Joined: Sun Jul 19, 2009 6:02 pm
Location: KL

Re: Issue with route given by GPS

Postby DPBaker » Mon May 23, 2011 2:33 am

That may be true except that:

- the gps changed speed when I changed speed - I deliberately went from 80 down to 60 and the gps changed accordingly - I went through these tunnels 4 times over a 2 day period so had plenty of testing time.

- I am very used to my own gps and I know how long before it looses lock in the Genting tunnel and the Curve tunnel - usually just before the end or just at the end. The tunnels in Singapore are maybe 5 times as long, yet it never lost lock once.

So, I can't really explain it. And to put it in context - I have been an Electronics Engineer for over 30 years and my company specialises in tracking equipment (for ships and helicopters) using GPS, so I work with GPS every day.

User avatar
Inggo
Contributor
Posts: 1093
Joined: Mon Jul 13, 2009 8:36 am
Location: N04'37.399"E103'12.484" MyGPS,Nuvi,PapagoX2/X3/X5 Mapking, I-GO, GarminXT GoSPEED
Contact:

Re: Issue with route given by GPS

Postby Inggo » Mon May 23, 2011 3:31 am

Simulated Gps in tunnel working with Papago, but not more than 2 minutes.
There was gps repeater for L1/L2 RF signal in singapore tunnel.
Image
Image
Image
...maybe the -m'force'm- will be with you, always.. :peace:
:mrgreen: Skywalker

User avatar
wblee
Posts: 219
Joined: Tue Jun 08, 2010 12:11 pm
Location: Ampang Selangor (realme GT neo 3)
Contact:

Re: Issue with route given by GPS

Postby wblee » Mon May 30, 2011 11:02 am

I asked a fren in Singapore to test GPS in tunnel.
He tested tunnel at Kalleng-PayaLabar Expressway (KPE), and it fail with iphone GPS with papago. And giving woring location with iphone GPS + A-GPS with google maps.
it should be no GPS signal inside the tunnul.


Return to “SG Archives”

Who is online

Users browsing this forum: No registered users and 13 guests