GPS best practices for low visibility?

[DougPaul]

I guess no one uses those bamboo sticks- or are they used for marking safe places to cross a crevasse?

They are called wands. We used them on the Katahdin to mark where the Abol slide trail left the tableland.

Doug

 

[sardog1]

I will cheerfully and publicly admit error if I am successfully contradicted on any of what follows. Otherwise, here's the multipart answer to the original question:

NOBODY publishes mapping software right now that is current enough, accurate enough, and comprehensive enough to rely on for low visibility navigation in the Whites.

The AMC publishes the definitive maps of White Mountains trails, plus their maps have all the topographic info you'll need for navigating. Yes, the maps employ that old technology that is so last millennium, i.e., paper. Yes, the AMC scales are a little weird, but you can work around that -- see below. (Corollary: If you cannot work around the weird scales, you might want to improve your map-using skills before attempting the low visibility stuff in the mountains.) There are also a couple other sources of reliable paper maps, the Randolph Mountain Club being one. Another is an excellent map and trail book that covers the Whites but which I hesitate to recommend for general use because of some metric funkiness.

Why do you care about paper maps in this digital age? Because they're integral to solving the original question:

Use the AMC maps (or their kin) to identify critical features and note the features' coordinates on a pretrip plan. (See Chauvin Guides web site for an example of a pretrip plan for a Presis traverse.)

How will you find the coordinates of said critical features? You'll use Maptools.com to generate a grid tool. You'll then use your printer's scaling feature to resize that grid tool to fit the scale(s) of the AMC map(s) that you'll be using. Yes, it will involve a tiny bit of algebra to determine the percentage for resizing.

Then you'll take the printed grid tool to a photocopier and make a copy on the clearest, thinnest transparency material that you can find. Then you'll cut off the excess transparency material around the edges. The result is a grid overlay tool that will fit in your pocket that is the same scale as the AMC maps.

Then you'll go back to Maptools.com for tutorials on how to use coordinate systems. Once you know how to do that, you'll use your overlay tool to plot the coordinates of any point in the Whites that's of interest to you.

Last step: Enter those critical coordinates in your GPS. It doesn't matter whether your GPS can display a map or not; you will still know where the critical features are in relation to where you're standing. And while you're on the route you've planned, you'll add coordinates of other critical features you've noticed along the way.

Oh, your batteries are cold and/or dead? Or you are deep in a drainage, surrounded by the forest not-so-primeval and not receiving satellite-based position fixes? No matter -- your pretrip plan is in your pocket, ALONG WITH YOUR MAP AND COMPASS!

Yes, it sounds like a lot of folderol. But if you follow this nearly-twelve-step program, you'll be far down the trail of enlightenment. And the other kids on your block will be amazed at your navigational abilities.

 

[DougPaul]

My GPS eats batteries inthe cold (Magellan Meridian). I suggest Lithium batteries for the winter and for backup spares. I use rechargables for the primary batteries and if they die I have the Lithiums which are lighter and are said to last between 2 - 5 times longer and are minimally affected by cold. Slightly off topic but hope it's helpful.

The capacity of AA Lithiums, I believe, is on the order of 2500 mah, wt .5 oz. Typical NiMH rechargables have capacities between 2000 maH and 2500 mah and weigh about 2 oz each. Lithiums should be good to around -40F and NiMHs to something on the order of -20F.

Doug