Line-of-sight measurement is a technique that uses the crosshair reticle in a telescope along with a leveling staff to determine the horizontal distance and elevation difference between two points. This method relies on optical and geometric principles, allowing for simultaneous measurement of both distance and height. It's particularly useful in situations where direct measurement is difficult or impractical.
One of the key advantages of line-of-sight measurement is its ease of use and speed. It’s not affected by ground undulations, making it ideal for measuring distances in rugged terrain. However, its accuracy is relatively low, typically ranging from 1/200 to 1/300. Despite this limitation, it remains widely used in surveying, especially for broken or uneven areas.
The thumb distance estimation method is a simple, visual technique based on trigonometry. To estimate the distance to a target, extend your arm forward, raise your thumb, and align it with the target using one eye. Then switch eyes and observe how much the target has shifted relative to your thumb. The apparent shift, when multiplied by 10, gives an approximate distance. This method works because of the angle formed between your eyes and the target, and it can be quite accurate if practiced regularly.
In more formal surveys, line-of-sight measurement involves using a theodolite or similar instrument. The principle is based on triangulation and the properties of similar triangles. When the telescope is aimed at a target, the distance can be calculated using the formula D = K * l + C, where K is the multiplication constant (typically 100), and C is the additive constant (often close to zero). This allows for quick and efficient distance calculations.
For sloped terrain, the line of sight must be adjusted. In such cases, the vertical angle α is measured, and the horizontal distance is calculated using the cosine of that angle. The formula becomes D = K * l * cos²α, while the elevation difference is determined using tanα. These calculations ensure accurate results even when the line of sight is not perfectly horizontal.
During fieldwork, the process involves setting up the instrument at a known point, measuring the instrument height (i), and taking readings from the upper, middle, and lower crosshairs on the leveling staff. The vertical angle is then measured, and all values are used in the appropriate formulas to calculate distance and elevation.
This method is essential in many surveying applications, offering a balance between speed and practicality. While it may not be as precise as other methods like GPS or total stations, it remains a valuable tool in the field, especially when working with limited resources or in challenging environments.
wifi 6 xpon onu,ax3000 gpon onu,ax1800 catv gpon onu,ax1500 gpon onu,wifi 6 ont
Shenzhen Runtop Technology Co.LTD , https://www.runtoptech.com