Arbitrarily assume the instrument and level it.

1, any hypothetical instrument, level.

Center the tower gauge bubble.

2. Place the tower ruler on a known point, and center the bubble of the tower ruler (assuming the elevation of the known point is 500.000m).

Coarse aiming tower ruler

3. The level is roughly aligned with the tower ruler. After the crosshair of the eyepiece is adjusted clearly, adjust the objective lens to set the focal length at the tower ruler position (subject to the clear reading of the tower ruler), and adjust the horizontal micro motion so that the vertical line of the black crosshair is parallel to and on the tower ruler.

Read tower ruler reading

4. Read the tower ruler (assuming 1.550m), and then calculate the instrument elevation: 501.550m. ..

Center the tower gauge bubble.

5. After the bubble of the tower ruler is placed in the center of the unknown point, align the level with the reading (e.g. 1.200m), then the elevation of the unknown point can be calculated: h = 500.000+1.550-1.200 = 500.350m. ..

* * * with discussion.

6. If you don't understand anything, you are welcome to discuss it.