Receiving position

Few polar or ocean expeditions would dream of going without GPS.
Next to the larger, fixed units common on most ocean cruisers, there are excellent, small and versatile handheld units on the market.

Garmin leads the market with its eTrex Summit. This 150 gr. device has a GPS, electronic compass, and an altimeter calculating altitude from two sources; barometric pressure and satellite info! That's much better than the old altitude meters based on pressure only, but unfortunately, even this new two-source system is still not 100% accurate.

Another unit is the Silva Multi Navigator. This unit has basically the same features as the eTrex , except for the two-source altitude meter. However, it is bulkier and heavier. One advantage, though, is that the display tolerates temperatures down to -25

The eTrex is the most popular unit with most expeditions.

As with all liquid crystal displays; never turn them on if recently frozen. Let them thaw. In addition, although electronic navigation is extremely convenient, it should not be a substitute for a traditional compass and paper map. 

If out on an ocean voyage, do not settle for a fixed GPS unit only. The handhelds are great and cheap backups. Store the handheld in the oven for a possible Faraday's cage effect in case of lightning but don't forget to remove when baking:-).

A handheld GPS is also a great tool if you are shipwrecked and need to direct rescue to your life raft.

The Thuraya phone has a built in GPS, which could potentially be a good safety asset for climbers and trekkers. Stay posted for evaluations.

Several tiny GPS units can be synchronized to an iPAQ PDA, either through the Compact Flash port or by Bluetooth. Stay posted for evaluations.