1. Select suitable measuring points: select some suitable measuring points on the topographic map, and try to choose places with obvious topographic relief.
2. Determine the polar axis and pole: the polar axis is the main axis of the polar coordinate system and can be any straight line. Pole is the base point of polar coordinate system, and it is usually selected in a corner of the map.
3. Measuring distance and azimuth: Take the pole as a reference, measure the distance and azimuth between each measuring point and the pole. Distance can be measured with a range finder or measuring instrument, and azimuth can be measured with a compass or azimuth meter.
4. Coordinate calculation: According to the measured distance and azimuth, the polar coordinates of each measuring point can be calculated. Then convert polar coordinates into rectangular coordinates, and you can get the coordinates of each measuring point on the map.
The advantages of using polar coordinate method for large-scale topographic mapping are that it can reduce errors, improve measurement accuracy and avoid the accumulation of errors in the measurement process. In addition, this method can simplify the measurement process and improve the work efficiency.
In practice, we should pay attention to some details. For example, when choosing the polar axis, try to choose the direction perpendicular to the measurement direction, so as not to affect the measurement accuracy. At the same time, we should pay attention to the precision and accuracy of measuring instruments to ensure the reliability of measuring data.
In a word, polar coordinate method is a practical large-scale topographic mapping method, which can effectively improve the accuracy and efficiency of topographic survey. In actual operation, it is necessary to select suitable measuring points and instruments according to specific conditions and pay attention to operation details to ensure the accuracy and reliability of measured data.