Cognition in the Wild Ch. 2: "Navigation as Computation"

Theme of the reading
The first half of chapter 2 details the computational level description of navigation and presents the basic representational assumptions behind the modern system of navigation practiced in the developed nations. The computational level is important because it defines the activity of navigation at the most abstract level. This definition of navigation covers all known forms of navigation on earth, at sea, and in the air. The computational level description is given in terms of a number of simple, but fundamental, constraints. In order for any system to process information, there must be a commitment to represent information in some particular way and not in other ways. Modern "Western" navigation assumes a particular set of frames of reference and units of measurement. It is important to see that these commitments are historically contingent. That is, they depend on a string of historical events that could have come out differently.

Getting ready to read
Definitions:
Constraint. A constraint is a relationship between two or more entities such that limits on one entity imply or cause limits on other entities. This is an abstract way of describing relationships that make up all working systems. Many kinds of problem solving (including navigation) can be seen as a process of constraint satisfaction. Even though any single constraint may not determine a unique solution, a combination of constraints may be sufficient to determine a unique solution. For example, a single line of position provides a one-dimensional constraint on the position of a ship. A ship cannot determine its position from a one-dimensional constraint, because it could be anywhere along the line. A second line of position can be combined with the first to produce a unique two-dimensional solution for the position of the ship. The point where the lines cross is a unique position solution that simultaneously satisfies both constraints.

Reading
Orienting questions and issues to keep in mind:

You should understand the details of the representations (the units and the frames of reference well enough to see how they encode the information that counts as inputs and outputs of the navigation process.
Pay special attention to the summaries on pages 58 and 65.