The only known BACK-UP of the GPS when it malfunctions is your ability to use a military protractor and military compass. The RM Military Protractor is the only protractor with a printed formula and a diagram to align map grid north to match the compass magnetic north. Protractors without the conversion formula will provide a reading that is off the exact grid coordinate position. The GPS will not penetrate sandstorms rainstorms snowstorms smoke structures forest canopies and thick cloud cover.
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