Tacheometry it is a branch of angular surveying in which the horizontal distance from the instrument station to the staff and therefore vertical distance of a point are determined from instrumental observation. Changing is thus completely eliminated. Method is more rapid though less accurate as compared with chaining.
Objects of Tacheometry:
- Preparation of contoured maps or plans.
- Used in hydrographic surveys.
- Location survey for roads, railway, reservoir etc.
- One uses it for checking more precise measurements.
Principle of Tacheometry:
The principle of tacheometry is that one can enable to compute horizontal and vertical distance from reading upon a stadia rod and thus eliminate chaining operation.
Tachometer is used under following situation:
- When obstacles meets such as steep and broken ground, stretches of water or swamps, One adopts tacheometry as best from the speed and accuracy point.
- In rough countries both horizontal and vertical measurements are tedious and chaining is inaccurate, difficult and slow.
- Lastly in locating contours and filling in details in a topographic survey this method is usually the quickest and best.
Essential requirements of tacheometer:
- A tacheometer
- A levelling or stadia rod
- Firstly a tacheometer is usually a transit theodolite having a stadia diaphragm
- Lastly the telescope of tacheometer may be
- External focusing
- Internal focusing
- External focusing fitted with analytic lens.
Levelling staff or stadia rod:
- Firstly the stadia rod or staff rod used with the thermometer may be usual types of levelling staff having least count of 0.005 m
- Stadia rod usually in one piece but for ease of transport it may be folding or telescope.
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