Apr 06, 2020

(1) Measure the instrument constant on the azimuth angle of the known coordinates on the ground. Place the gyro theodolite** on the surface near the well point C (Figure 1a), measure the gyroscopic azimuth angle TCD of CD side, the coordinate azimuth angle αCD of CD side is known, the instrument constant △ is**

△ = ACD-TCD = αCD + γC-TCD

Where γC is the convergence angle of the meridian at point C, which is obtained from the rectangular coordinates of the Gaussian plane at point C. Point C is positive to the east of the central meridian, and negative to the west.

(2) Measure the gyroscopic azimuth on the downhole directional edge. As shown in Figure 1b, ab is the downhole directional edge, and the gyroscopic azimuth angle Tab is measured by a gyro theodolite, then the coordinate azimuth angle of the side is:

αab = Aab-γa = Tab + △ -γa

Where γa is the convergence angle of the meridian at point a.

(3) Determine the instrument constant again on the ground to improve the measurement accuracy and check. Use the average value of instrument constant to participate in the calculation.

Measure the gyro azimuth 2 to 3 times, and check the difference between the two measurements.

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