This document discusses different types of surveys based on accuracy, purpose, equipment used, and position of instruments. It also covers concepts like error in measurement, accuracy vs precision, most probable vs residual errors, theory of least squares, and measures of precision like standard deviation and modulus of precision. Surveys can be classified based on whether they account for earth's curvature, intended map use like control, topographic, or cadastral surveys, and the equipment employed like chain, theodolite, plane table, or photogrammetric methods. Random errors follow probability laws and can be minimized using least squares to find the most probable value.