The surveying work must follow some basic principles to guarantee the requirements of accuracy.
1. Layout：Integration to Part
2. Order: Control survey to Detail survey
3. Accuracy: High to Low
4. Procedures: Checking after each step
   Under these principles, the integrated accuracy in coverage control can be guaranteed and measurement cumulative error will be prevented. On the other hand, the whole survey area can be divided into several parts after the integrated control survey. In this way, all parts’ surveying work can be carried out at the same time, which will speed up the work.