What is the purpose of a compass radical survey?

The purpose of a compass radical survey is to establish the true bearing of each corner of a field. This technique involves using a compass to take precise readings of angles from a central point within the area being surveyed, which helps in accurately mapping out its boundaries and layout. By determining bearings, surveyors can locate points relative to a true north reference, ensuring that measurements are consistent and reliable. This is crucial for various applications such as land division, construction planning, and navigation.

In contrast, the other options focus on different objectives that are not aligned with what a compass radical survey achieves. For instance, calculating the area of a square field pertains more to geometric calculations rather than bearing establishment. Measuring elevation changes involves topographic surveys, and historical significance relates to archaeological studies, which do not utilize the compass technique for surveying purposes.