Global Positioning System (GPS) Classroom Forum

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TOM TOM XL question...
Posted by: JOE in MD
Date: October 31, 2011 06:15PM
Hi All,
I don't normally post here, but I do read a lot of post here. Anyway here's my question. I just took a trip to Time Square in New York. My TOM-TOM kept losing it's signal in and around New York area. I had another TOM-TOM last year and it did the same thing. I've been told about jamming signals around Time Square and other story. I figured it to be the tall buildings had something to do with it. I did see a cab driver who had a Garmin and it look like it was work fine. Do you think it's just the TOM-TOM GPS or something else. I have a Garmin 60CSx that I use in the woods and never have a problem with signals. Any help is appreciated.

Re: TOM TOM XL question...
Posted by: Andrew Kalinowski
Date: April 01, 2012 06:48AM
City canyons can be worst for GPS reception than the woods but, most modern receivers are so sensitive that it rarely poses a problem. Most but, not all. Could be that your TomTom was designed for open roads ;)

Andrew Kalinowski

Re: TOM TOM XL question...
Posted by: edjcox
Date: April 04, 2012 01:42AM
The GPS signals propagate in straight lines but will bounce on solid objects like building, bridges. The narrow city canyons obscure the direct line of sight for GPS units and movment will cause signal loss and reaquisition with that movement. Your GPS unit typicallly needs at least 3 signals to locate itself and 4 for altitude... If your losing line of sight constantly causes the reciever to introduce erors in the postion data and that's what your experiencing. Newer units are more sensitive. Also localizing your reciever sometimes enables it to more accurately predict sat positions and get a link.

In the city canyons lot of the GPS sats are simply not high overhead but nearer the horizon and therfore not in view for your machine. Turn a corner and the setup changes... A real troble are for most machines..

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