If it's on GNER it's to calculate when you get to your destination
My chum has a Garmin standalone unit.....think it is a MApquest or the like...anyway he has to use it powered from the cigarette lighter in his car, but it is quick to start up, easy to read and navigate via a large screen and can be shoeved into his flightcase when he leaves the car.
I've been considering the Navman 510, which is battery as weel as DC powered. Price about £350 at LHR.
Anyone got one and care to comment on it?