Tacheometric Surveying Problems Pdf Download
Tacheometric Surveying Problems Pdf Download
Tacheometric surveying is a method of rapid surveying that uses a tachometer to measure the horizontal and vertical distances between two points. It is useful for surveying in difficult terrains where direct measurements are not possible or convenient. However, tacheometric surveying also has some problems and limitations that need to be understood and overcome by the surveyors.
Problems of Tacheometric Surveying
Some of the common problems of tacheometric surveying are:
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Error in stadia constants: The stadia constants, which are the ratio of the focal length to the distance between the stadia hairs and the additive constant, are assumed to be constant for a given instrument. However, they may vary due to temperature changes, wear and tear, or improper adjustment of the instrument. This can cause errors in the calculation of distances and heights.
Error in staff readings: The staff readings, which are the difference between the top and bottom stadia intercepts, are affected by the accuracy of the staff graduation, the alignment of the staff with the line of sight, and the atmospheric refraction. If the staff is not held vertically or if there is a difference in air density between the instrument and the staff, the staff readings will be erroneous.
Error in vertical angle: The vertical angle, which is the angle between the horizontal plane and the line of sight, is measured by the vertical circle of the tachometer. The accuracy of this angle depends on the adjustment and calibration of the instrument, as well as the levelness of the instrument station. Any error in the vertical angle will affect the computation of heights and slopes.
Error in horizontal angle: The horizontal angle, which is the angle between a reference direction and the line of sight, is measured by the horizontal circle of the tachometer. The accuracy of this angle depends on the orientation and adjustment of the instrument, as well as the stability of the instrument station. Any error in the horizontal angle will affect the computation of bearings and directions.
Solutions for Tacheometric Surveying Problems
To minimize or eliminate the problems of tacheometric surveying, some possible solutions are:
Checking and adjusting stadia constants: The stadia constants should be checked and adjusted periodically by using a standard distance or a calibrated staff. The instrument should also be protected from extreme temperatures and shocks that may alter its settings.
Improving staff readings: The staff should be graduated with fine and clear markings that can be read easily. The staff should also be held vertically and aligned with the line of sight as much as possible. The atmospheric refraction can be reduced by using a short staff or by taking readings at dawn or dusk when the air temperature is uniform.
Correcting vertical angle: The vertical angle should be measured with care and precision by using a sensitive level bubble or a plumb bob. The instrument should also be leveled properly before taking readings. The vertical angle can also be corrected by applying a correction factor based on the latitude and elevation of the station.
Correcting horizontal angle: The horizontal angle should be measured with accuracy and consistency by using a reliable reference direction or a magnetic compass. The instrument should also be oriented correctly before taking readings. The horizontal angle can also be corrected by applying a correction factor based on the magnetic declination and local attraction.
Pdf Download for Tacheometric Surveying Problems
If you want to download a pdf file that contains some solved examples of tacheometric surveying problems, you can click on one of these links:
[Tacheometry - Problems]
[Tacheometry - Solved Examples]
[Tacheometry - Practice Questions]
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