Wild Heerbrugg 2m subtense bar
Wild Heerbrugg 2m Invar subtense bar
A 2 m long Invar (not prone to temperature changes) subtense bar ('basislatte'). This was used for measuring distances with a theodolite. The precise length of the bar would be used together with the two angles measured towards it to trigonometrically calculate the distance to the target. The centre of the bar would function as target for the third, angular measurement (or the average of the two outer could be taken). Folded, the bar is slightly over 1 m long.
For work at night the targets can be illuminated using a standard battery box. To align the bar perpendicular to the theodolite (to avoid measuring errors due to the bar being at an angle), the bar has its own sighting telescope next to the centre. Though technically this will still give a small error due to the offset, it is so small that it can be neglected.
I have both an old model as well as a newer model. The main difference lies in the central construction with a different method of clamping the two halves and a different type of sight. The newer model seems to have a sight that can be used from the theodolite apart from a collimation sight for rough direction. This would allow the theodolite observer to accurately sight in the bar rather than the operator of the bar having to do this. This saves on training the operator vs giving instructions from the theodolite observer to the operator of the bar.
Wild 2m BL16-23
Data sheet
- Serialnumber
- 13555
58265 - Type of use
- Survey
- Material
- Brass
Steel - country obtained from
- United Kingdom
Venezuela
You might also like
8 other products in the same category:
Wild Heerbrugg 2m Invar subtense bar