C. A Perfect 2D Grid?

1. Defining a Grid Coordinate System  

A grid coordinate system must be carefully designed to ensure that:

•  grid and horizontal ground distances match
•  grid and horizontal ground angles match.

These, in turn, preserve shape and area of measured quantities.

An "ideal" grid coordinate system should have these three characteristics:

a. Orthogonal

The system consists of two reference axes are right angles to each other, Figure C-1

Figure C-1 Reference Axes

These define Grid North and Grid East for the system.

b. Parallel meridians

All meridians are parallel with the North reference axis, Figure C-2, with no convergence.

Figure C-2 Parallel Meridians

Forward and back grid directions always differ by exactly 180°.

c. Uniform scale

A linear unit is the same physical length regardless its orientation, Figure C-3.

Figure C-3 Uniform Scale