timcodes

Hi Everyone,

This is my first experience with a gps, I can say it saved our trip completely! I have the bt-338 unit with mapopolis and truely, it saved us many times once we were lost!

our Trip was from toronto-quebec-montreal, not once I had to open up my map, not once I lost fix!! Incredible!!

Although I do have a question, in the downtown area such as montreal, sometimes the signal would jump around, however in old quebec where the buildings were not as tall (but still tight) it was 100% accurate.

Is this common or is my unit defective?

Thanks, truely I would recommend this gps to everyone! :)

JakeRich

In tall building areas, called "urban canyons," the signal can jump around due to a phenomenon called multipathing. The signals from the satellites can bounce off buildings and be received by the GPS as a more strong signal than the signal coming directly through the buildings, so that extra distance for the bounce is used in the fix calculation, making it wrong. When you start to receive the stronger signal directly again, the bounce distance is corrected, making the fix jump again. There isn't really any good way to correct the problem, unfortunately. But, it's rare except in the urban canyons of really big cities.

timcodes

Thanks for the reply JAakeRich.

Ah Then, I guess my unit is not defective and it is a common problem with gpses correct?

JakeRich

Some are better than others. The 338 is one of the better ones.