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and where θ
H
is the angle of the horizontal component of the magnetic field vector measured
clockwise from the positive y-axis. Defined in this way, θ
H
is also the heading of the sting in
"mathematical" compass coordinates:
When the sting is pointing: θ
H
is:
North +90°
East 0°
South -90°
H
Horizontal
Horizontal
HY
HX
θ
tan=
West 180°
Consider an example. The magnetic flux vector in the vicinity of the McLane Research
Laboratories points towards the magnetic north pole and downward at an angle that is ~70° below
the horizontal. The table below shows measured values for HX, HY, and HZ for various
magnetic pointing directions of the sting. Calculated values of φ, and θ
H
are also included.
Sting
Direction
HX HY HZ φ θ
H
N 90° 0.3645 0.0008 -0.9312 -68.6° 82.8°
NE 45° 0.2383 0.2321 -0.9430 -70.6° 37.7°
E 0° -0.0246 0.2914 -0.9563 -73.0° -7.4°
-45° -0.2508 0.1515 -0.9561 -73.0° -53.7°
S -90° -0.3212 -0.1064 -0.9410 -70.2° -101.2°
-135° -0.3218 -0.9259 -143.1°
W 180° 0.0511 -0.3652 -0.9295 -68.4° 174.7°
NW 135° 0.2817 -0.2563 -0.9246 -67.6° 130.4°
SE
SW -0.1979 -67.8°
Appendix D-6