The design-data survey is followed by the construction survey that consists broadly of the LAYOUT or STAKEOUT survey and the AS-BUILT survey, which will be discussed later in this chapter. In a layout survey, both horizontal and vertical control points are located and marked (that is, staked out) to guide the construction crews. Figure 14-31 identifies various stakes and hubs used in highway or road construction and their typical arrangement. The functions of the various stakes and hubs are described briefly as follows:

1. CENTER-LINE STAKES indicate the exact center of the roadway construction.

2. SHOULDER STAKES are used to indicate the inside edge of the roadway shoulders. These stakes are set opposite each center-line stake.

3. REFERENCE HUBS, as the name implies, are used to reference other stakes or to aid in establishing or reestablishing other stakes.

4. SLOPE STAKES mark the intersection of side slopes with the natural ground surface. They indicate the earthwork limits on each side of the center line.

5. RIGHT-OF-WAY STAKES indicate the legal right of passage and outmost bounds of construction.

6. GRADE STAKES indicate required grade elevations to the construction crews. During the final grading stage of construction, hubs called "blue tops" are used in lieu of stakes. The blue

Figure 14-31 .-Typical arrangement of various hubs and stakes on a road section (final grading).

tops are driven so that the top of the hub is set at the required grade elevation.

7. GUARD STAKES are used to identify and protect hubs. The face of the stake is marked with station identification and is placed so that the stake faces the hub it identifies. Sometimes more than one guard stake will be used to protect a hub.

8. OFFSET STAKES may be additional stakes that are offset a known distance from other stakes that will likely be disturbed during construction. The offset stake is marked with the same information as the stake it offsets, and it is also marked to show the offset distance. Often, stakes will themselves be offset a known distance from their true location. This eliminates the requirement for additional stakes.