As there is height transfer from Wong Yi Chau to Tai Tau Chau, reciprocal leveling is needed to minimize the effect of the atmosphere as well as the line of sight and curvature corrections. As a result, total station will be calibrated before performing reciprocal leveling. Line-of-sight error and V-Index are determined through calibration.
Line-of-sight error and V-Index
The line-of-sight error or collimation error (C) is the deviation from the perpendicular between the tilting axis and the line of sight. The effect of the line-of-sight error increases as the vertical angle becomes larger. For V-index, the vertical circle should read exactly 90° (100 gon) when the line of sight is horizontal. The difference will be called vertical index error.
1. A point was aimed approximately 15 m from the product which is within 20° of the horizontal. 2. Horizontal and vertical readings were taken.
3. Telescope position was changed by face left and face right. 4. A same point was aimed and horizontal and vertical readings were taken again. 5. A prism was aimed and measurement is triggered.
6. The line-of-sight error and V-Index will be shown in the screen. Fig. Calibration of Total Station
| Horizontal Reading| Vertical Reading|
FL| 00-00-00| 90-53-22|
FR| 179-59-59| 269-6-48|
| | |
| delta Hz| delta V|
| -00-00-01| -00-00-02|
Fig. Result of calibration
According to the result obtained, the line-of-sight error is 1 seconds while the V-index is 2 seconds which is acceptable and very small.