Target height
The value you enter in the Target height field depends whether you are measuring:
-
the true height of the prism
-
to the notch on a traverse prism base
True height
The default Target height measurement method is to measure the true height of the prism. Measure to the center of the prism.
Notch on a traverse prism base
When measuring the target height to the notch on a traverse prism base, tap 
in the Targets screen and select S notch. The S notch corresponds to the Bottom notch on a Spectra Geospatial FOCUS instrument.
The Origin software corrects the measured slope value to true vertical and adds the appropriate offset value to calculate the true vertical height to the center of the prism.
| Value | Definition |
|---|---|
|
Ho |
Offset from the notch to center of the prism. For the S notch this value is 0.158 m (0.518 sft). |
|
Hm |
Measured slope distance. |
|
Hc |
Hm corrected from slope to true vertical. |
|
HT |
True vertical target height. Hc + Ho. |
If you select S notch, the minimum slope distance (Hm) that you can enter is 0.300 meters. This is approximately the minimum slope distance that can be physically measured. If the minimum is not low enough, you must measure the true height to the center of the prism.
