What is distance measurement and what methods can be used to measure it?

In geological surveying and mapping in the common distance measurement, angle measurement and so on. Today's chapter, jiangxi province mapping instrument network will be introduced to friends is the distance measurement of knowledge, I hope you buy equipment to help. Knowledge 1: Understand the definition of distance measurement distance, that is, the two points on the ground along the plumb line direction in the projection on the level of the arc length between the two points, because of the irregularity of the ground level, for the distance measurement has increased a certain degree of difficulty. However, if the measurement range is small and the radius is less than 10 kilometers, the horizontal surface can be used instead of the level surface. The main work of distance measurement is to measure the horizontal distance between two points, friends can use a steel tape measure, latitude and longitude, total station and GPS and so on. With a steel tape measure along the ground to measure the distance, called the steel measuring tape distance; the use of longitude and latitude instrument or total station, etc. for sight distance wire and sight distance ruler according to geometric optics principles of ranging, known as the sight distance measurement; the use of two GPS receivers to receive the satellite precision ranging signals, by the distance of the spatial rendezvous method of ranging distance, i.e., GPS measurements. In addition, there are electromagnetic wave ranging, acoustic wave measurement and so on.