When measuring power lines, the direction of turning points is usually determined on-site based on the route specified in the preliminary design at a scale of 1/10000. The biggest challenge is that the turning directions on the drawings cannot be directly applied to practice. If the direction is determined by measuring angles on the drawings, the error will be over 2%. To achieve accurate orientation and improve measurement efficiency, a simple and practical method, the reference object orientation method, has been developed in actual measurement work. This article will introduce this method. [b]1 Determining Reference Objects[/b] The prerequisite for accurately selecting reference objects is that the designers should conduct a thorough and detailed site survey during the preliminary design. Following the path selected on the drawings, upon arriving at the turning point on-site, find tall, obvious, and fixed visible reference objects in the direction of the line turn, such as existing power line towers, water towers, or distinctive buildings. After accurately marking these reference objects on the drawings (if the reference object already exists on the drawings, it will be more accurate), the direction of the turning point can be determined and calculated. 2 [b]Determination and Calculation of Turning Angle Direction[/b] Analyzing the relationship between on-site reference points and the track, two situations may arise: the reference point is within the length of the track's tension section, and the reference point is outside the length of the track's tension section. The methods for handling these two situations differ. 2.1 Reference Point Within the Length of the Track's Tension Section When the selected reference point is within the length of the track's tension section, measure the horizontal distance from the turning point to the reference point on the drawing, and measure the vertical distance from the reference point to the track's forward direction (or the control distance between the track and the reference point). Based on the trigonometric relationship between these two, trigonometric functions can be used to calculate the horizontal angle between the track direction and the line connecting the turning point to the reference point, and the average of these values ​​is taken. Then, align the theodolite with the reference point and rotate it horizontally according to the calculated angle value (note that the direction of rotation must not be incorrect). The resulting direction is the required track direction. See Example Figure 1. [img=250,211]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/zjdl/2001-5/64-1.jpg[/img] As shown in Figure 1, during the measurement of the 35 kV long-distance line, the Y2-Y3 tension section is approximately 2.2 km long. The drawing shows that there is a two-story house on the left side of the line 600 m away from the Y2 turning point in the direction of the line's advance. Due to other constraints, the initial design of the line was to pass close to the house while maintaining a safe distance from it. According to the regulations, the safe distance between the 35 kV line side conductor and the house should be 3 m when considering the maximum wind deflection, and the maximum extension of the line crossarm beyond the center of the line should be 2.8 m. After appropriately considering a margin, the line was determined to pass 10 m away from the wall. The average value was calculated to be α = 0°57′17.65″. The theodolite was aligned with the corner of the wall and turned to the right at an angle above the corner. The actual distance measured at the house was 10.7 m, with an error rate of 0.12%, meeting the design requirements. [img=305,87]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/zjdl/2001-5/65-1.jpg[/img] 2.2 Reference Object Located Outside the Length of the Current Tension Section When the selected reference object is located outside the length of the current tension section of the line, first draw the line connecting the current turning point to the reference object on the drawing. Then measure the vertical distance from the next turning point to that line, and then measure the length of the current tension section. Using these two values, calculate the required deflection angle using the calculation method described above. Then, align the theodolite with the reference object and rotate it horizontally by the corresponding angle. The resulting direction is the required line direction. See Example Figure 2. [img=300,249]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/zjdl/2001-5/65-3.jpg[/img] As shown in the figure, during the measurement of the 35 kV long-haul line, the Y7-Y8 tension section is approximately 2.0 km long. There is a 500 kV transmission tower 2.5 km from the Y7 turning point. Using this tower as a reference, the vertical distance from the line connecting Y7 and the tower to Y8, measured on the drawing, is 25 m. Using trigonometric functions, the average value was calculated as α = 0°42′58.3″. The theodolite was aligned with the 500 kV tower and turned to the right at an angle greater than 5°. Moving in this direction to Y8, the measured distance from the actual required fixed point was 5 m, with an error rate of 0.25%, meeting the design requirements. [img=301,80]http://zszl.cepee.com/cepee_kjlw_pic/files/wx/zjdl/2001-5/65-2.jpg[/img][align=center]Take the average α＝0°42′58．3″[/align][align=left][b]3 Conclusion[/b] Based on the analysis of the above application examples, it can be seen that the reference object orientation method is very simple, practical, and has small errors. If there are no obvious reference objects on site, this method is not applicable, but this situation only occurs in sparsely populated areas. In such places, even if the error in the line turning angle is large, it will not affect the passage of the line. Therefore, the reference object orientation method is the preferred method for orientation in line measurement work in congested areas.[/align]