On The Ground
Surveyors used various instruments for projects like mapmaking, building and siting channels for water supply and drainage. Reliable measurements could be derived by applying simple geometry to the information these instruments provided about distances, heights and angles. In China, astrological instruments guided placements of many structures.
This instrument, with vertically swinging telescope, measures distances.
With its adjustable sighting rule and scales of degrees, the theodolite measures horizontal angles, a basis for calculating ground distances.
In China, south was the most important direction. Specialists in feng shui used the central compass to find advantageously oriented sites to place graves, homes and other structures.