What are the traditional surveying and mapping methods?

According to the way of obtaining measurement results, measurement can be divided into direct measurement and indirect measurement. Direct measurement allows the measured object to be directly compared with the measurement unit, or uses a pre-calibrated measuring instrument to obtain the measured value. Indirect measurement is to obtain the measured value by directly measuring other variables that have a certain functional relationship with the measured, and then calculating according to the function. Combination measurement: In the measurement, each unknown quantity appears in a different combination form. According to the data obtained from direct measurement or indirect measurement, simultaneous equations are established through various conditions to obtain the values of unknown parameters, which is called combined measurement.