Determine how the grid is laid out. The simplest type of grid is a matrix of equal sized squares. These grid squares are formed from two sets of parallel lines, a set of equidistant – spaced horizontal parallel lines and a set of equidistant-spaced vertical parallel lines. The vertical parallel lines are perpendicular to the set of horizontal vertical lines.
Associated with each vertical line and each horizontal line is a label that identifies the name of each line. For many road maps, the horizontal line labels are of sequential numbers. The lowest horizontal line is most often labeled 1, the one above that labeled 2, the one above that 3 and so forth. The vertical lines are also labeled sequentially; however, often letters are used instead of numbers. The left most vertical line is often labeled A; the second, B; the third, C; and so forth.
Determine the location of the each line associated with the individual coordinates that needed to be found. For a two-dimensional map grid, the location of a street in the street index might be labeled as A3. In this example, the vertical line is be labeled A and the horizontal line is labeled 3. To locate the grid coordinate A3, first locate the vertical line labeled A, and then locate the horizontal line labeled 3.
Find the intersection point of the horizontal line and vertical line by following the vertical line up until you reach where it intersects with the horizontal line. In the example of the coordinate A3, follow the vertical line A until it intersects with horizontal line 3. The intersection point is the location of the A3 coordinate.