SURVEY POINT MARKERS

are generally classified as field supplies. Because SEABEEs operate in so many different places and under such varied conditions, we have not tried to list in this training manual the supply requirements for every location. From your own experience and with the aid of your leading petty officer, you can easily make a list of supplies necessary for a projected survey mission. Those items generally required for a mission are described in this section. SURVEY POINT MARKERS The material used as a SURVEY POINT MARKER depends upon where the point is located and whether the marker is to be of a temporary, semipermanent, or permanent character. For example, a wooden stake can be easily driven to mark the location of a point in a grassy field, but it cannot be used to mark a point on the surface of a concrete highway. Similarly, though a wooden stake may be easily driven in a grassy field to mark a property line corner, a marker of this kind would not last as long as a piece of pipe or a concrete monument. Most of the material commonly used as semipermanent or permanent markers of points in the field is described in the following sections. For purely temporary marking, it is often unnecessary to expend any marking materials. For example, a point in ordinary soil is often temporarily marked by a hole made with the point of a plumb bob, a chaining pin, or some other pointed device. In rough chaining of distances, even the mere imprint of a heel in the ground may suffice. A point on a concrete surface may be temporarily marked by an X drawn with keel (lumber crayon), a pencil, or some similar marking device. A large nail serves well as a temporary point in relatively stable ground or compacted materials. Semipermanent Markers Wooden hubs and stakes are extensively used as semipermanent markers of points in the field. The principal distinction between the two is the fact that a hub is usually driven to bring its top flush with, or almost flush with, the ground surface. A hub is used principally to mark the station point for an instrument setup. It is usually made of 2- by 2-in. stock and is from 5 to 12 in. long. The average length is about 8 in. Shorter lengths are used in hard ground, longer lengths in softer ground. A surveyor’s tack, made of galvanized iron or stainless steel with a depression in the center of the head, is driven into the top of the hub to locate the exact point where the instrument is to be plumbed. Stakes improvised in the field may be either cylindrical or any other shape available. However, manufactured stakes are rectangular in cross section because the faces of a stake are often inscribed with data relevant to the point that the stake is marking. A stake that marks a bench mark, for instance, is inscribed with the symbol that identifies the bench mark and with the elevation. A stake that marks a station on a traverse is inscribed with the symbol of the particular station, such as 2 + 45.06. A grade stake is inscribed with the number of vertical feet of cut (material to be excavated) or of fill (material to be filled in) required to bring the elevation of the surface to the specified grade elevation. Figure 11-56 shows typical dimensions for an average-sized hub and stake. These dimensions, however, may be modified as situations arise, such as material limitations. Permanent Markers Permanent station markers are used to mark points that are to be used for a long period of time. Horizontal and vertical control stations are Figure 11-56.-Hub and stakes. 11-47