Construction Surveys
Layout fundamentals
Construction surveying transfers design positions to the ground. Control is established first, then offsets, hubs, and stakes are set from that control. Stationing notation combines station and offset (for example 12+45.00, 25 ft left). A benchmark is the vertical reference; every stake has an elevation and an offset from a reference line.
Cut and fill
Grade is expressed as cut (dig) or fill (place). A typical grade stake reads "C 1.2" or "F 0.8" relative to the design elevation at that point. The arithmetic trap: cut is the amount the design grade is below existing ground; fill is the amount above. Slope stakes are set where the side slope intersects existing ground, using the catch distance derived from the design cross-section, offset, and depth.
Horizontals, verticals, and tolerances
Horizontal curve staking uses deflection angles and chords from the PC, with the PI, PT, and delta angle given. Vertical curves are parabolas; the high or low point occurs where the grade changes sign, at x = L·g₁/(g₁ − g₂) measured from the BVC. As-built surveys verify the constructed work against design, and machine control relies on the same 3D model with its own tolerance and calibration checks.
Worked example
Design elevation 104.20 ft, existing ground 105.50 ft at a stake: difference is 1.30 ft, and since the ground is higher than design, it is a cut of 1.30 ft. If the ground were 103.60 ft, it would be a fill of 0.60 ft.
Trap to watch
Stationing is not a coordinate and cannot be used interchangeably with a state plane value. Also watch sign conventions: a negative cut is a fill, not an error to report.