ARMY TM 9-6675-349-12&P
MARINE CORPS TM 11039A-12&P
b. Vertical Angle Measurement.
(1) With theodolite auto-reflected on porro prism, point theodolite telescope so the center horizontal
crosshair is on an edge of the porro prism
(2) Measure and record vertical angle to porro prism.
(3) Plunge theodolite telescope, point it so the center horizontal crosshair is on the same edge as in
step (1), and measure and record reverse vertical angle to porro prism.
(4) Repeat measurements if difference between direct and reverse pointings is greater than 0.2 mil.
(5) Mean direct and reverse pointings to obtain mean vertical angle.
c.
Mean Horizontal Angle Measurement. Not required for position update or position, only mark.
(1) Auto-reflect on porro prism.
(2) Measure and record direct angle from porro prism clockwise to azimuth target.
(3) Plunge theodolite telescope and measure and record reverse angle from azimuth target to porro prism
(auto reflect).
(4) Repeat measurements if difference between direct and reverse pointings is greater than 0.2 mil.
(5) Mean direct and reverse pointings to obtain mean horizontal angle.
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