Measuring the instrument height

There are two measurement marks on the side of the instrument.

• The true height mark corresponds to the trunnion axis of the instrument.

• The bottom notch height mark is 0.138 m (0.453 ft.) below the true height mark. Measure the bottom notch height mark to the top ridge of the notch.

1

True height mark

2

Bottom notch height mark

The measured distance (Hm) is corrected for the slope of the measurement to obtain a vertical measurement to the bottom mark (Hc). The constant from the bottom mark to the top mark (0.138 m/0.453 ft.) is added to the Hc to obtain the vertical instrument height from the ground mark to the trunnion axis (Ih). For more information, refer to the field software documentation.

Alternatively, to obtain an accurate measurement to the true height mark (HI), you can manually measure the slope distance from the ground to the bottom notch height mark (Hm). To calculate the total instrument height (HI), insert the measured slope distance (Hm) into the formula below: