ABSTRACT

Calculating the location, height, area, perimeter, volume, slope, aspect, distance between two points, line of sight between two points on the Earths surface etc. are some of the most fundamental and common computations in GIS. Advanced GIS often computes the azimuth and elevation of celestial objects from the Earth’s surface and the almanac data pertaining to every location on the Earth for a given date and time. Sometimes an applicationspecific GIS can compute path profile between source and destination, crest clearance of a projectile, elevation profile of a terrain cut and radio line of sight between source and destination. Generally a GIS toolkit should have some of these computing tools in various forms. In this chapter we discuss the numerical formula of a representative set of such tools. It is not exhaustive as the set is ever increasing, with more sophisticated spatial computations emerging day by day.