First of all, what do you mean by "a map"? A nautical chart? A WAC, or aeronautical sectional? A 1:50,000 topo? A street map?<br><br>Second, who said anything about navigating to safety? I was thinking of sending out an SOS on my FT-817 (a 5-watt portable capable of sending and receiving morse code on short wave). Yeah, I suppose the SAR guys could home in on my transmission - if my AA alkalines didn't die in the meantime - but how much better it would be if I could give an approximate lat/long for them to start searching?<br><br>Finding the approximate longitude isn't hard, as long as you have a reasonably accurate wristwatch. I have Zulu time (aka UTC or GMT) programmed into mine, but as long as you know what time zone your watch is set to, you can figure that out. Note the time (UTC) when the shadow is shortest (that's what I call 'local solar noon' - I'm sure there's a technical term for it). Subtract 12 hours; if the answer is negative, add 24. Express the number of minutes as a fraction; e.g. if it's 1634 hours (that's 4:34 p.m.) then your number is 4-34/60, or about 4.56. Divide by 24 and multiply by 360 (or if you're lazy, just multiply by 15) to get 68.4 - approximately 68 degrees 24 minutes West. (I'm purposely doing the math in my head, so I may have screwed up; if it was a l&d sitch, or if my numbers were clearly out to lunch, I'd sacrifice some of my Rite-in-the-Rain paper to doublecheck it :-)<br><br>If you're out hiking - or even driving - and get lost, you probably don't need this. If you've got a GPS, make sure you record your position *before* the batteries die. <br><br>But if you're like one of those unfortunate Chilean soccer players, and you've been rudely awoken out of a nice comfortable sleep to find yourself surrounded by dead team-mates and a whole bunch of snow blowing through a gaping hole in the fuselage, it might be nice to be able to estimate your position, even if only to locate yourself quickly on the pilot's map.