Surveying computations are an integral part of the surveying profession. Until only a few decades ago they were performed by logarithms, mechanical calculators and slide rules. Mathematical models had to be given in forms suitable for the computational means available to the profession. The invention of digital or high-speed electronic computers led to a revolution in data handling and problem solving practices. The application of modern computers and calculators in surveying necessitates a radical reorganization of scientific research and everyday engineering work. Analytical methods of computations have not lost their importance, although the domains of their applications have changed. Computers brought a variety of numerical methods which, together with approximation theory, have become the most important part of surveying computations.