Dig out the maps.....
Which brings me to something. I have used my Global Map 100 for several years without problem, but they don't make this model anymore which is very unfortunate. So I was browsing CRAIGS LIST one day and saw one... excellent condition, all the papers, box etc for $50! So I contacted the guy right away and bought it. So I now have two of my favorite GPS, and two DGPS antennas. Too bad I cannot find a spare beacon receiver. Lowrance stopped building them and they're scarce.