This unit considers how to construct digital objects—i.e., points, lines and areas—out of sets of coordinates and how to represent their attributes and relationships. Strategies for representing this information in a GIS database are presented and illustrated with examples, and issues with each are discussed.

This unit reviews a few simple algorithms that are fundamental to the topics of later units, which describe how complex operations are constructed. It begins with a definition of algorithm and heuristic, then walks through an example of the steps required to assess whether two simple lines intersect. Special cases where this method fails are noted, and heuristics are presented for assessing whether complex lines intersect.

This unit considers how the geometry of lines and areas is coded in a GIS database. Different techniques for coding straight lines, arcs of circles, and splines are presented, and advantages and disadvantages of each are discussed.