Originally Posted by Rogue Wave
is the antenna in a car GPS more sensitive than a seperate antenna as supplied with most marine units
Most modern ones yes !!!
Most modern in car sat nav systems use GPS receivers with the SIRF chip sets.
Traditional GPS systems used to ignore weaker satellite signals as they were potentially rebounds from terrain or building and would only take a fix from the stronger (direct) signals received.
SIRF however processes ALL the signals even the weaker potentially rebounded ones and based on analysing several readings calculates with some fantastic bit of software the most likely fix.
The SIRF system is ideal for use in cars where the receiver is traditionally mounted in side the vehicle and the vehicle its self is often in and out of hostile terrain (well hostile to satellite signals anyway) as it can maintain accurate fixes with far fewer and far weaker signals form the satellites.
As far as I know - marine gps do not use the SIRF chip sets in the GPS recievers as having to deal with weaker signals in the open ocean never occurs.