What are the two main branches of geodesy?

The two main branches of geodesy are physical geodesy and geometric geodesy. Physical geodesy pertains to the measurement and understanding of the Earth's physical properties, including its shape, gravity field, and how these attributes can be used to derive information about the Earth's structure and dynamics. It involves studying phenomena such as isostasy and sea level changes, which are crucial for understanding the Earth's interactions with forces such as gravity.

Geometric geodesy, on the other hand, deals with the measurement of the geometric relationships between points on the Earth's surface. This branch focuses on deriving the precise positions of points using techniques such as triangulation, trilateration, and satellite positioning systems like GNSS (Global Navigation Satellite Systems). It is essential for applications in mapping and surveying, where accurate positioning is critical.

Together, these two branches provide a comprehensive framework for understanding and utilizing Earth's measurements in both theoretical studies and practical applications. The other options, while they involve geodetic concepts or applications, do not define the fundamental categories of geodesy used in academic or professional contexts.