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i use a cell phone with GPS and some app for Android(offline maps, topography charts, gpx routes).
A cheap chinese phone($120) GPS have like 5-9 meter precision...put all in a waterproof bag.
also go with a battery bank($30) is like 4 - 5 day energy for the cell phone without sollar power.
if have signal you can also make a call in phone ...upload photo, call help
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