Plain-language definitions for survey, grading, pipe installation, horizontal alignment, machine guidance, and field documentation terms. 54 terms across 6 categories.
An as-built drawing (also called record drawing or red-line drawing) is a set of construction plans marked up to show the actual constructed positions of all improvements, deviations from design, and field changes.
Field DocumentationAn as-built survey documents the actual constructed positions of installed improvements — pipes, structures, road centerlines, and utilities — as opposed to the design positions shown on construction plans.
Field DocumentationA backsight is a rod reading taken to a point of known elevation — typically the benchmark — immediately after the leveling instrument is set up.
Survey & LevelingA benchmark is a surveyed point of known elevation used as a reference datum for construction grade work.
Survey & LevelingBenchset refers to the initial elevation establishment procedure on a construction project — verifying the benchmark, connecting to a control network, and setting the reference elevation for all subsequent grade work on the job site.
Survey & LevelingBlade control refers to the automated or semi-automated adjustment of a motor grader or dozer blade elevation and cross-slope based on input from a machine guidance system.
Machine GuidanceA blue-top stake (also called a grade stake or hub) is a wooden stake driven so that its top is at the design grade elevation, allowing a grading equipment operator to use the tops of the stakes as a direct grade reference.
Grade & EarthworkA catch basin is an inlet structure in a storm drainage system with a sump at the bottom designed to capture sediment and debris before stormwater enters the pipe system.
Pipe & DrainageA control line is a surveyed reference line established on a construction site from which horizontal measurements are made to set the location of structures, pipes, road edges, and other improvements.
Survey & LevelingA control point is a surveyed location with known coordinates (northing, easting, elevation) used as the starting reference for layout and grade work on a project.
Survey & LevelingCross-slope is the transverse slope of a road or surface measured perpendicular to the direction of travel.
Grade & EarthworkThe crown of pipe is the highest interior point of a pipe's cross-section — the top of the inside of the pipe.
Pipe & DrainageA curb inlet is an opening in the vertical face of a road curb that admits stormwater runoff into the storm drain system.
Pipe & DrainageA cut stake is a grade stake where the existing ground elevation is higher than the design grade, requiring material to be removed (cut).
Grade & EarthworkA daily field report (DFR) is a written record of construction activities completed on a given day, including crew sizes, equipment deployed, work performed, quantities installed, weather conditions, and any issues or delays.
Field DocumentationA design surface is a three-dimensional terrain model representing the finished grade of a construction project as designed by the engineer.
Machine GuidanceDifferential leveling is the surveying process of determining elevation differences between points by measuring backsight and foresight rod readings from a level instrument.
Survey & LevelingDrain slope is the grade percentage or ratio at which a drainage pipe is installed to ensure adequate gravity flow.
Pipe & DrainageA fill stake is a grade stake where the existing ground elevation is lower than the design grade, requiring material to be added (filled).
Grade & EarthworkFinal grade is the finished elevation of a constructed surface after all grading, paving, or concrete work is complete — the last-placed layer at its design elevation.
Grade & EarthworkA foresight is a rod reading taken to a point of unknown elevation after a backsight has established the Height of Instrument.
Survey & LevelingA grade check is a field verification shot taken to confirm that installed construction (subgrade, pipe, curb, concrete) is at or within tolerance of the design elevation.
Grade & EarthworkGrade percentage is the ratio of vertical rise to horizontal run, expressed as a percent.
Grade & EarthworkA grade rod is a numerical value representing the distance from the top of a grade stake (or instrument sight line) to the design subgrade elevation.
Grade & EarthworkA headwall is a concrete or masonry retaining structure at the inlet or outlet of a culvert or storm drain pipe, designed to prevent erosion, retain the embankment, and control flow.
Pipe & DrainageHeight of Instrument (HI) is the elevation of the horizontal line of sight through a level instrument at a specific setup location.
Survey & LevelingA hub and tack is a precision staking method where a wooden hub (stake) is driven close to design elevation and a surveyor's tack (small nail) is driven into the top of the hub at the exact design location, providing both a precise horizontal position and elevation reference.
Survey & LevelingAn in-cab display is the screen inside a grading machine (dozer, motor grader, excavator) showing the operator real-time information from the machine guidance system — current blade elevation, cut/fill to design, cross-slope, and alignment position.
Machine GuidanceInstrument height (also called Height of Instrument or HI) is the elevation of the line of sight of a leveling instrument at a given setup location.
Survey & LevelingThe invert elevation is the elevation of the lowest inside surface of a pipe, channel, or culvert at a specific point.
Pipe & DrainageThe Point of Curvature (PC) is the point where a tangent alignment transitions into a horizontal curve — the beginning of the curve.
Horizontal AlignmentThe Point of Intersection (PI) is the point where two tangent lines of a horizontal curve intersect.
Horizontal AlignmentPipe fall is the total vertical drop across a pipe run, calculated as the pipe length multiplied by the grade percentage divided by 100.
Pipe & DrainagePipe grade is the slope of a gravity pipe, expressed as a percentage or ratio of vertical fall to horizontal run.
Pipe & DrainageThe Point of Tangency (PT) is the point where a horizontal curve ends and the alignment returns to a tangent (straight) section.
Horizontal AlignmentA punch list is a document prepared near the end of a construction project that lists incomplete or defective work items that must be corrected before the project receives final acceptance.
Field DocumentationResection is a surveying technique where an instrument is set up at an unknown location and oriented by taking observations to two or more known control points to calculate the instrument's position.
Survey & LevelingRip-rap is a layer of large, angular stones placed to protect soil surfaces from erosion caused by water flow — typically at culvert outlets, channel banks, and slope faces.
Pipe & DrainageA rod reading is the numerical value observed on a leveling rod (grade rod, Philadelphia rod) through the crosshair of a level instrument.
Survey & LevelingRough grade is the approximate graded elevation established by earthmoving equipment after bulk cut and fill operations are complete, typically at a specified tolerance above the finish subgrade to allow for base course material.
Grade & EarthworkA shot log is a field record of survey observations — elevations, positions, and descriptions of points measured during grade verification, as-built surveys, or layout work.
Field DocumentationThe spring line of a pipe is the horizontal plane passing through the center (widest point) of the pipe cross-section.
Pipe & DrainageA station equation is a notation that reconciles a discontinuity in stationing along a highway alignment, typically caused by alignment revisions during design.
Horizontal AlignmentSubgrade is the compacted native or imported soil layer that forms the foundation beneath road base, pavement, or structure slabs.
Grade & EarthworkA submittal is a document or sample submitted by a contractor to the engineer or owner for review and approval before a material or product is incorporated into the work.
Field DocumentationTraverse closure is the process of verifying the accuracy of a series of connected survey measurements by returning to the starting point and calculating the misclosure — the difference between the computed and known coordinates of the starting point.
Survey & LevelingA turning point is a temporary point used in differential leveling to allow the instrument to be moved forward while maintaining an elevation reference.
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