The importance of keeping the line of sight high above ground surface

In surveying, it is crucial to ensure that the measured angles and distances are as accurate as possible. One way to minimize the error in the observed angles is by keeping the line of sight high above the ground surface. This is because of several factors that may affect the accuracy of the measurements, such as:

Shimmering

Shimmering is the effect of the atmosphere's turbulence, which causes the air to move in random directions, creating a distorted image. This effect is more pronounced when the line of sight is close to the ground surface, where the temperature gradient is steeper. By keeping the line of sight high above the ground surface, the shimmering effect is reduced, resulting in more accurate measurements.

Horizontal refraction

Horizontal refraction is the bending of light that occurs when it passes through layers of air with different densities. This effect is more pronounced near the ground surface, where the temperature gradient is steeper. By keeping the line of sight high above the ground surface, the horizontal refraction effect is reduced, resulting in more accurate measurements.

Vertical refraction

Vertical refraction is the bending of light that occurs when it passes through layers of air with different densities. This effect is more pronounced when the line of sight is close to the ground surface, where the temperature gradient is steeper. By keeping the line of sight high above the ground surface, the vertical refraction effect is reduced, resulting in more accurate measurements.

Conclusion

In conclusion, keeping the line of sight high above the ground surface is essential to minimize the error in the observed angles due to shimmering, horizontal refraction, and vertical refraction. This ensures that the surveying measurements are as accurate as possible.

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