AVERAGE ANGLE METHOD
This method assumes a straight line between survey stations A and B. The inclinations and directions are averaged. The objective is to calculate the following for the survey point B in the diagram below:
— TVD
— North Co-ordinate
— East Co-ordinate
— Vertical Section (VS)
— Dogleg Severity (DLS)
|
|
|
East |
According to the diagram above:
aA + aB л — x. ,
a = —- = average drift angle
2
в = Pa + вв = average azimuth angle
AB = MDB — MD = course length PB = course displacement = AB sin a
(i) True Vertical Depth of Station B:
PA = true vertical distance = AB cos a
|
(ii) North and East Co-ordinate of Station B: PC = North Displacement (AN) = PB cos p CB = East Displacement (AE) = PB sin p |
|
|
|
T |
From the plan view of the above:
NB = Na + AN
Eb = Ea + AE
(iii) Vertical Section of Station B:
From the plan view of the above:
Vertical section (VS) = OX = OB cos 0
closure OB = «JeB + NB
|
= El N |
0 = Angle TON — Angle BON (target bearing — bearing of B)
tan (Angle BON) =
Dog leg severity = cos-1( cosaA cosaB + sinaA sinaB cos (PA — PB))