11 3 T ra v er sing Be thor oughl y f amiliar with the use of y our com pass and GPS unit Bef ore depar ture check that the magne tic declination and GPS se ttings are correct f or the area Check that these instruments are w or king correctly while y ou still kno w y our location so that y ou can trust the instrument readings lat er Y ou ma y ha v e t o depend on y our instruments As such carr y an e xtra se t of batt eries f or the GPS A GPS unit doe s no t remo v e the need t o carr y a map and com pass or eliminat e the need f or skills t o use them Y our GPS unit ma y no t giv e reliable readings in hea vy timber or st eepw alled can y ons A ttach y our instruments t o y our body or pack or st o w them in pock e ts which can be closed up Losing eq uipment is po t entially danger ous and costly in time and effciency The com pa ss needle aligns with the str ongest magne tic feld and theref ore ma y pr oduce inaccurat e readings when near belt buckles magne t or lan y ar d clips ir on f ormations or ultramafc r ock Check accuracy b y taking bearings back t o w ar d y our last com pass checkpoint No t e natural indicat or s of general direction such as a bright er sky in the east in the morning and w est in the e v ening moss on the nor th side of the trees w e tt er slopes and indicat or s of cooler micr oclimat e on the nor th side of mountains Alw a ys n av igat e when y ou are tra v elling in the feld This req uires checking com pass bearings k eeping track of time and possibly pacing a sim ple means of measuring linear distance b y w alking