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3. Azimuth
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Figure F-2 Azimuth Observation |
Equation F-4 is the angle of a line from the meridian in terms of a its coordinates.
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Equation F-4 |
A: At point |
The angle from the meridian can be to the right (+) or to left (-) depending on the coordinate differences signs. This places the angle in one of the four quadrants, Figure F-3.
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Figure F-3 Angle from Meridian |
The value of QAT, added to the angle to obtain the azimuth, depends on the quadrant. Table F-1 shows the sign of α, its quadrant and QAT value.
Table F-1 Azimuth for a Line ij by Quadrant |
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Partial derivatives of Equation F-4 are taken with respect to each coordinate of both points. The partial derivative for NF is:
Remaining partial derivatives are:
Equation F-5 is the azimuth observation equation, evaluated at initial coordinate approximations.
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Equation F-5 | |
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Equation F-6 |