The main classes of surveying are geodetic surveying, topographic surveying, cadastral surveying, construction surveying, and hydrographic surveying. Geodetic surveying deals with large areas and high accuracy measurements for mapping the Earth's surface. Topographic surveying focuses on determining the natural and man-made features of a specific area. Cadastral surveying involves demarcating property boundaries. Construction surveying is done to guide the construction of infrastructure and buildings, while hydrographic surveying is used to map underwater features.