Locating Corner Points

We cannot describe here all the methods of locating a point with reference to a horizontal control point of a known horizontal location. We will take the situation shown in Figure 25 as an example. This figure shows two horizontal control points, consisting of monuments A and B. The term monument doesn’t necessarily mean an elaborate stone or concrete structure. In structural horizontal control, it simply means any permanently located object, either artificial, such as a driven length of pipe, or natural, such as a tree, of known horizontal location.

In Figure 27, the straight line from A to B is a control base line from which you can locate the building corners of the structure. You can locate corner E, for example, by first measuring 15 feet along the base line from A to locate point C; then measuring off 35 feet on CE, laid off at 90° to, or perpendicular to, AB. By extending CE another 20 feet, you can locate building corner F. Corners G and H can be similarly located along a perpendicular run from point D, which is itself located by measuring 55 feet along the base line from A.