FS Module 1: Surveying Processes & Methods

What is a boundary survey?

A survey that establishes or retraces the lines and corners of a parcel of land based on record documents, evidence found in the field, and applicable law.

What is an ALTA/NSPS Land Title Survey?

A boundary survey performed to specific standards jointly adopted by the American Land Title Association and the National Society of Professional Surveyors. It includes boundary, improvements, easements, and encroachments and is required by title insurers for commercial transactions.

What is the fundamental principle of EDM (Electronic Distance Measurement)?

EDM instruments measure distance by transmitting an electromagnetic signal to a reflector and measuring either the phase shift of the returned signal or the time of flight. Distance = (speed of light x time) / 2, with corrections for atmospheric conditions.

What atmospheric corrections must be applied to EDM measurements?

Temperature and barometric pressure corrections. Higher temperatures decrease air density (signal travels faster, measured distance appears shorter). Higher pressure increases air density (signal travels slower, measured distance appears longer). The correction is typically parts per million (ppm).

What is differential leveling?

A method of determining elevation differences by measuring vertical distances from a horizontal line of sight to points on the ground. The instrument is set up between a backsight (BS) on a known point and a foresight (FS) on the unknown point. Elevation = known elevation + BS - FS.

What is reciprocal leveling and when is it used?

A method used to cross wide obstacles (rivers, valleys) where normal balanced setups are impossible. Readings are taken from both sides of the obstacle to cancel curvature and refraction errors. The mean of the two elevation differences is used.

What is trigonometric leveling?

Determining elevation differences using a measured slope distance and vertical angle: Delta-h = S x sin(alpha), where S is the slope distance and alpha is the vertical angle from horizontal. Must correct for curvature and refraction over long distances.

Name the five main GNSS surveying methods.

1) Static - long occupation (1-2+ hrs), highest accuracy 2) Rapid Static - shorter occupation (5-20 min) 3) RTK (Real-Time Kinematic) - real-time cm-level positions, needs base station or network 4) PPK (Post-Processed Kinematic) - similar to RTK but corrections applied after 5) CORS/OPUS - uses Continuously Operating Reference Stations; OPUS processes data through NGS

What is PDOP and why does it matter for GNSS surveys?

Position Dilution of Precision - a dimensionless number describing the geometric strength of satellite configuration. Lower PDOP = better geometry = more precise positions. PDOP < 3 is ideal; PDOP > 6 indicates poor geometry. PDOP combines HDOP (horizontal) and VDOP (vertical).

What are the minimum field note requirements for a survey?

Field notes must include: date, weather conditions, crew members, instrument type and serial number, setup locations, raw observations (angles, distances, rod readings), sketch of work, point descriptions, and any anomalies observed. Notes should be recorded in ink at the time of observation.

What is the 3-wire leveling method?

A precise leveling technique where three crosshair readings (upper, middle, lower stadia hairs) are recorded for each rod observation. The mean of the three readings reduces reading errors, and the stadia interval (upper - lower) provides a distance check for balanced sights.

What OSHA excavation depth requires a protective system (shoring, sloping, or shielding)?

5 feet (1.5 m). Excavations 5 feet or deeper require a protective system unless the excavation is made entirely in stable rock. A competent person must inspect trenches daily and after any hazard-increasing event.

What is the prism constant and how does it affect EDM measurements?

The prism constant is the offset between the physical center of a prism and its effective optical center (where the signal is reflected). It is typically -30 mm for standard prisms. If not correctly set in the instrument, all distances will have a constant systematic error.

What is a construction survey?

A survey that establishes horizontal and vertical positions of planned improvements (buildings, roads, utilities) so they can be built according to design plans. Includes staking out offsets, cut/fill grades, slope stakes, and alignment control.

What is the purpose of a topographic survey?

To locate and map the natural and man-made features of the earth's surface, including elevations (represented by contours), roads, buildings, utilities, vegetation, water features, and other significant details within a defined area.

What is a closed traverse and why is closure important?

A traverse that returns to its starting point or connects to another known point. Closure allows computation of angular and linear misclosure, which indicates the quality of the survey. The closure ratio (linear misclosure / total traverse length) must meet project standards (e.g., 1:10,000 for boundary surveys).

What does "Call Before You Dig" (811) require?

Federal law requires notifying the One-Call center (811) at least 2-3 business days before any excavation. Utility companies then mark the approximate location of underground facilities. Surveyors must call before driving stakes, monuments, or rods that require penetrating the ground.