What is one of the primary functions of an astronomical survey?

One of the primary functions of an astronomical survey is to image regions of the sky. This process involves capturing detailed observations and images of celestial objects, enabling astronomers to study various cosmic phenomena, such as stars, galaxies, nebulae, and the cosmic background. These surveys are crucial for expanding our understanding of the universe, as they allow researchers to map the distribution of astronomical entities and gather data about their properties, like brightness, distance, and motion.

The other options, while important in their respective fields, do not pertain directly to the focus of astronomical surveys. Mapping surface terrain and assessing water bodies fall under topographic and environmental surveying, while measuring land use is related to planning and land management activities, none of which align with the functions of observing and analyzing celestial bodies in the context of astronomy.