Tacheometry is a method of surveying in which horizontal distances, and differences in elevations are determined by measuring intercepts on a graduated scale and angles using theodolite. The word tacheometry derives from greek word ‘tachus’ meaning swift and ‘metron’, meaning measure. This method is also known as tachemetry or telemetry.
Advantages of Tacheometric Surveying
The advantages of tacheometric surveying over the direct method of measuring horizontal distances and difference in elevations are:
- Speed of surveying is very high.
- Accuracy of surveying is quite satisfactory in normal conditions and even superior in difficult terrain.
- Cost of surveying is less.
- Not tedious as chain, tapes, ranging rods, etc, are avoided.
- The method is more advantageous in the following works:
- Preparation of topographic plans.
- Reconnaissance surveys for roads and railways.
- Hydrographic surveys.
- Checking already measured distances.
- For filling in details in a traverse.
Different systems of Tacheometric Measurements
- Stadia system which is further divided into
- Fixed hair method.
- Movable hair method.
- Tangential method of tacheometry, and
- Substance bar method of tacheometry.