What is the name of the grid system that uses letters along the top and numbers along the sides of a drawing?

The grid system that uses letters along the top and numbers along the sides of a drawing is known as the coordinates system. This system provides a simple way to reference specific points in a two-dimensional space, facilitating accurate communication of design dimensions and locations.

In architectural and engineering drawings, this grid format allows for straightforward identification of locations within the drawing by combining a letter and a number, which represents a specific intersection on the grid. For example, point A3 would indicate the location that is found where the grid line marked "A" intersects with the line marked "3." This method offers clarity and precision, especially in complex designs where locating elements quickly is essential.

While the other terms relate to aspects of drafting or design, they do not refer specifically to this method of referencing locations within a drawing. Indexing pertains to organizing information, plotting refers to the action of marking points on a graph or diagram, and dimensioning involves adding measurements to drawings to illustrate sizes and distances, but none of these terms describe the grid reference system as effectively as coordinates.