Navigation with Distance, Time, and Pace (XIII)
By Robert Finlay of KayakLakeMead.com
Edited by Federico Ferrero
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USING an ALTIMETER to DETERMINE POSITION: An accurate altimeter is sometimes invaluable. Three things to keep in mind are; ( 1) Get a good one; on the rare occasions when you use an altimeter you'll want accurate readings, (2) Its readings will vary with local atmospheric pressure changes; so occasionally reset it during your trek at known elevation positions such as on hilltops, and (3) if you are ascending or descending very fast your altimeter will not "keep up with you", there will be a lag time; stop, wait a couple of minutes and then read it.
1. Descending a Steep Mountain in Limited Visibility Using Altimeter and Compass:
You are at the top, at WP 4, at 9960', and in the clouds and descending to WP 5. Visibility is 100'. Your altimeter works just fine. You need to know where WP 3 is; because that denotes the ridge leading to WP 5. I don't think time and distance will be a lot of help in finding WP 3; however always estimate the distance and keep an eye on the time you spend moving. It is just too steep, too foggy, and there is just too much brush and too many rock bands to contend with; to have any realistic idea of your pace down.
ref: map A3, Willow Peak.
Pace: It is uphill the whole way but if you keep your speed at 9.0 km/hr then your...
Notice the elevations shown on the map are in meters not feet.
Altimeter: Your elevation right now is 3035 m. The elevation at WP 3 is about 2560 m.
Altimeter and Compass: Execute your descent in legs (orange dots); (1) to the saddle, (2) @ 18° to 2850 m, (3) 0° to 2700 m, (4) 13° to 2560 m. when your altimeter indicates between 2570 and 2550 m, always give yourself a "window", you should be able to continue your descent, on a bearing of 56° (the orange arrow), right down to WP 5 and out of the clouds.
Notes: The ridge down to WP 3 is wide but be sure you stay on it. If you change your direction to 56° too early you'll end up in a drainage to the right of "your" ridge (pink circle) which also bears about 56° and will lead to WP 5. If you overshoot WP 3 you'll end up in a drainage (pink arrow) which will eventually bear north. In either case you should be able to think your way through it.
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