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E4004 Surveying Computations A. Two Missing Bearings. Derivation of Formula. Consider line RS. If distances RP and PS are known the position of P is also known. The intersection of two distances. S. P. R. Derivation of Formula. But P could also lie on the other side of RS.
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E4004 Surveying Computations A Two Missing Bearings
Derivation of Formula • Consider line RS • If distances RP and PS are known the position of P is also known • The intersection of two distances S P R
Derivation of Formula • But P could also lie on the other side of RS • There are always two solutions in a two missing bearing problem P S P’ R
Derivation of Formula • From a surveying viewpoint • In the triangle RSP the bearing and distance RS will be known and the distances SP and PR will be provided D1 P S • The direction of the bearings are important D2 MB MD R
Derivation of Formula • We have a triangle with three known sides • Each angle can be solved with the cosine rule D1 P S D2 MB MD R
Derivation of Formula a B D1 P S C D2 MB c MD b R A
Derivation of Formula a b B D1 P C S A C a D2 MB c MD b c R A B
Derivation of Formula • The same formula apply for the second triangle • Again the bearing directions are important P S MB D1 MD P’ R D2
Derivation of Formula • Angles R & S have been calculated RIGHT of line RS B1 P LEFT of line RS S S S B2 MB B1’ MD R P’ R R B2’
Summary of Formula LEFT of line RS RIGHT of line RS B1 P S S S B2 MB B1’ MD R P’ R R B2’