In general, control surveys deal with established points. To define these points, surveyors

have to mark them. Certain points are made permanent; on the other hand, others are temporary. A line that will be used for a long period of time, for example, may be marked at each end with a bronze disk set in concrete, or with a center-punched metal rod driven flush with the ground. For less permanent control points, wooden stakes or hubs with nails, shiners, and flaggings can be used.

A DRIVEN MARKER must be set exactly vertically on the point it is supposed to mark. If it is driven on a slant, the top of the marker will not define the correct location of the point. To drive the marker vertically, first align it vertically; then, using a sledgehammer or other type of driving implement, strike each blow squarely on the flat end of the hub or stake.

A wooden hub is normally driven to mark the exact horizontal location of a point, usually for the purpose of plumbing an instrument over the point. Consequently, it is not normally necessary for the top of a hub (or other markers used for the same purpose) to extend much above the ground line. The precise location of the point is marked by a hub tack, punch mark, or other precise marker driven or set in the top of the hub. For work on asphalt roads or runways, youll find it easier to use flagging or a soda pop top and a nail as a marker; in concrete and other hard surfaces, you can use orange paint or a star-drilled hole plugged with lead. The choice of markers to be used depends on the surveyors judgment as well as the purpose of the survey.

In frozen or otherwise extra hard ground, use a bull-point to start a hole for a stake or hub. Remember that the stake or hub will follow the line of the opening made by the bull-point. Therefore, if the bull-point is not driven vertically, the stake or hub will not be vertical either.

In surveying, a MONUMENT is a permanent object or structure used where a point or station must be retained indefinitely for future reference. It may simply consist of a conspicuous point carved on an outcrop of a ledge rock or otherwise constructed in concrete. Figure 12-7 shows common types of concrete monuments. The top of the monument should have an area large enough to include the required point and any necessary reference data. The depth of the monument should be sufficient to extend below the frost line. If the depth of the frost line is unknown, a minimum depth of 3 ft is generally accepted. Other factors, such as soil condition and stability of foundation, may also affect the depth of the monuments. The area should be checked out for soil stability to provide an adequate foundation. A monument settles in the same manner as any other structure if an adequate foundation is not provided.

The exact location of the point on a monument may be marked by chiseling an X on the surface or by drilling a hole with a star drill and hammering in a lead filler or grouting in a length of brass stock (often called a COPPER). When grouting a copper, you should use neat cement grout because a fluid grout would flow into and fill the small space around the copper. If the point can be placed at the same time as the monument is being cast in place, the copper can be pushed down into the surface of the monument before the concrete begins to harden. If you are near an armory, you may be able to obtain large, expended brass shell casings. The primer end of a shell casing makes an excellent survey point marker when it is embedded in a concrete monument.

With a little imagination and ingenuity, you can easily design and construct adequate survey monuments when they are required.