The basic positioning elements in surveying works are distance, angle and elevation and those elements will be affected by external environment like temperature and air pressure. The basic measurement unit in surveying is mainly refer to length (or altitude difference), angle, area, temperature, air pressure, tension force etc.

The basic unit of elevation and distance is meter (m)

The basic unit of angle is degree (°)

The basic unit of area is square meter (m²)

The basic unit of temperature is centigrade (℃)

The basic unit of tension force is Newton (N)

The basic unit of air pressure is Pascal (Pa)