A point is marked with the information required to identify the point and with any other relevant data. Temporary identification marks can be made with keel. More permanent marks can be made with paint. An even more permanent mark consists of a metal plate set in concrete.

A. point that indicates a traverse station is marked with the symbol or number of the station, such as STA. B or STA. 21. A point on a stationed traverse is marked with the particular station, such as 2 + 87.08. Frequently, a point will serve as a traverse station and a bench mark. A bench mark is marked with an identifying symbol and usually with the elevation. In marking such an elevation, do not use a decimal point, as in 317.22 ft. Instead, raise the figures that indicate the fractional part and underline them; for example, 3172Z ft.

All control points should be tied in or referenced. The ties or reference points are

recorded in the field book as they are established in the field. The record may be done either by sketch, by work description, or by the combination of the sketch and notes. The control point must be referenced to some permanent type of object in its vicinity; if no such objects exist, REFERENCE HUBS are driven at points where they are unlikely to be disturbed. These ties are important in recovering control points that have been covered or otherwise hidden or in reestablishing them accurately if they have been removed.

The reference location of a particular point is recorded on the remarks page of the field book by sketches like those shown in figures 12-8 and 12-9. For a permanent control point, such as a triangulation point, monument, or bench mark, a complete "Station Description" is individually prepared for each station. The field offices of the National Oceanic and Atmospheric Administration or the National Geological Survey have these station descriptions on separate cards. This is done so they can easily run a copy for anyone requesting a description of a particular station. They also maintain a vicinity map on which these

Figure 12-8.-Natural objects or man-made structures used as reference points.

points are plotted, and these station descriptions are used in conjunction with this map. The Navys public works offices also maintain descriptions of stations within their naval reservation and its vicinity for immediate reference.

The methods of referencing points shown in figure 12-8 are ideal for recovering points that have been covered or otherwise hidden, and those shown in figure 12-9 are for reestablishment of these points accurately. The methods shown in figure 12-9 are generally used in construction surveys.

As you gain more experience, you may be assigned the task of writing a station description. In doing this, be sure to describe the location in detail, and make a sketch showing the location, ties, and magnetic or true meridian. Make your description concise and clear; and be sure to test its effectiveness by letting another EA (preferably not a member of the survey party that established the point) interpret your description. From the feedback of the interpretation, you can determine the accuracy of your written description. Your description, for example, should be written as follows (refer to figure 12-8): "Point Aplugged G.I. pipe 65.21 ft SE of NE corner of PWC Admin. Bldg. (Bldg. 208) and 81.42 ft from the SE corner of same building. It is 18.18 ft W of the center of a circular manhole cover located in Saratoga Street."

Markers are to be protected against physical disturbance by the erection of a temporary fence (or barricade) around them. Sometimes guard stakes embellished with colored flaggings are simply driven near the hub or similar marker to serve as deterrence against machinery or heavy equipment traffic. On the other hand, permanent markers are protected by fixed barricades, such as steel or concrete casing.