Peter Bennett wrote:
On Mon, 23 Apr 2007 18:36:22 -0400, Keith nuttle
wrote:

Cna the functionallity needed of a GPS for navigating on water be
combined with the functionality need for navigating on roads and high
ways.

I would be nice to have one unit for in the car and on the boat.

A GPS receiver optimized for road use is likely to be pessimized for
marine use :-)

It seems that many of the road-use receivers have features like "road
lock" - as long as the GPS position is within some small range of a
road, the GPS will show you as on the road, rather than where you
actually are. I saw one boater complaining that while he was passing
under a bridge, the (road-aware) GPS suddenly showed him on the bridge
and adjacent road, rather than in the river where he really was.

Land-oriented receivers may also omit the very useful "highway"
display that shows cross-track error and relative bearing-to-waypoint,
as it is of very little use while driving but essential (IMHO) on the
water.

On my Garmin one can easily turn off the road lock and either the
highway maps or waterway maps, as needed. It seems to work great for both.

Stephen