This interesting and useful manual is meant to provide the background and context for a set of software that assists marine scientists to carry out GIS (Geographical Information System) analysis of multiple marine data sets. For most of its history, marine science suffered from the problem of data sparseness. When the shipborne oceanographic station (taking 12 hours or more for a shallow and deep cast using Nansen bottles) was the main means of gaining knowledge about the nature of the ocean, knowledge grew very slowly. It was thought valid to create oceanographic atlases, to which every expedition would contribute new data, in the belief that data from different years and seasons could be combined to gradually build up a three-dimensional map of an unchanging ocean. Now we know better, but our recognition of the rapidly changing nature of the ocean has come about only because of the advent of a host of new oceanographic measurement techniques that generate data at unprecedented rates, both in space and time. Given that a typical oceanographic survey may involve the use of a large number of such techniques to map several different ocean parameters simultaneously, we are reaching the point of data overload, where instead of being data sparse, the ocean becomes too data rich for us to fully understand the picture built up by the measurement systems and especially the relationships among different ocean parameters.