Surveying: Terms and Definitions

General Surveying Terms

• Accidental errors are purely accidental and caused by factors beyond the surveyor's control, present in all surveying measurements
• Accuracy refers to the absolute nearness of observed quantities to their true value
• An Aidman's duty is to provide first aid treatment to the survey party in case of bites, accidents, and other health and safety-related situations
• Assistant chief of party helps the chief of the party
• An assumed meridian is an arbitrarily chosen fixed line of reference taken for convenience, often the direction from a survey station to an adjoining station or other permanent point
• Atmospheric refraction is the deviation of light or electromagnetic waves from a straight line due to variations in air density with height
• An Axe man/Lineman clears the line of sight of trees, brush, and other obstructions
• Backsight distance is measured from the instrument's center to the rod on which a backsight is taken
• Backsight is a reading on a rod held on a point of known or assumed elevation
• A benchmark is a fixed point of reference with a known or assumed elevation
• Cadastral Surveys are usually closed surveys defining property lines, boundaries, corners, and areas in urban and rural locations
• Chains and Tapes are tools used to measure linear distances in surveying
• The chief of party has overall responsibility for direction, supervision, and operational control of the survey party
• A clinometer measures the angle or elevation of slopes
• A compass is a hand-held instrument determining the horizontal direction of a line with reference to the magnetic meridian
• Computations are usually made algebraically using simple arithmetic and trigonometric functions
• The computer's duty is to perform all survey data computations and the necessary computational checks
• Control stations are small marks set immovably in the ground, allowing instruments or targets to be set up with millimeter accuracy in the horizontal plane
• Control Surveys provide horizontal and vertical positions of points to which supplementary surveys are adjusted
• Curvature describes the state of being curved or bent
• Differential leveling is a technique determining elevation differences between remote points
• Direct leveling involves establishing a horizontal line of sight, measuring the elevation difference where the rod is held
• Direct measurement involves comparing the measured quantity with a standard measuring unit
• Double-Rodded Leveling is a method for determining elevation differences using two level routes simultaneously, differing from conventional leveling by establishing two turning points for independent backsights and foresights
• Ellipsoidal or geodetic height is the distance represented by a coordinate pair on the reference ellipsoid to the Earth's surface, measured perpendicularly to the ellipsoid
• Explanatory Notes provide a written description of field activities
• A flagman holds the flagpole or range pole at selected points as directed by the instrument man
• Foresight distance measures the horizontal distance from the instrument's center to the rod where a foresight is taken
• Foresight is a reading on a rod held on a point to determine its elevation
• Full stations are points established along a profile line route at uniform measurement intervals

Other Terms

• Distances are usually made in multiples of 100, 50, 30, 20 or 10
• Geodetic Surveying is surveying including the spheroidal shape of the earth
• GIS (Geographic Information System) a computing system for capturing, storing checking and displaying data
• Grid Meridian is a fixed line of reference parallel to the central meridian in rectangular coordinates
• Head tape man is responsible for measuring tape
• Height of Instrument or Collimation is the elevation of line of sight of an instrument from a datum
• Horizontal control consists of 2 or more points established accurately and precisely
• Horizontal datum fixes a position correlated to latitude and longitude
• Hydrographic surveys study oceans, lakes, streams and other bodies of water
• Indirect Measurement is using an instrument when measuring directly is impossible
• Instrument man sets up and operates levels and equipment
• Intermediate foresights or ground rod readings are taken along a center line to represent ground surface
• Land Information System (LIS) a geographic system for local governments
• A level can read elevation and determine differences
• Leveling determines the vertical position of different points
• LiDAR(Light Detection and Ranging) uses remote sensors and reflected light to measure distances
• Local attraction is deviation from the compass' normal magnetic north
• Magnetic Meridian is a fixed line parallel to earth's magnetic field as measured by a compass
• Meridian lies in a vertical plane passing through a fixed reference point
• Mine surveys locate underground excavations as well as geological formations
• Monuments include land boundary survey corners
• Orthometric height is the distance from the geoid to the point, aligned with the plumb
• The pacer makes sure all tape measures are accurate
• Parallax is the apparent movement of objects from different positions
• Photogrammetric Surveys (Aerial Surveys) use cameras on planes or the ground
• Plane surveying considers the world as a flat surface
• Plus stations are intermediate ponts on a profile level route
• Poles Tripods and Mounts keep laser and level equipment solid
• Precision describes the observations value to another.

Terms Continued

• Prisms and Reflectors keep control points safe
• Probability describes a likely occurrence over all possibilities
• Profile is a curved line which portrays an intersection of a plane
• Profile leveling is the process of elevation along a line at measured intervals
• The rear tape man assists the head tape man
• The recorder keeps record of sketches and necessary observations
• Reference datum measures an unknown point by using a known one.
• Rodman stands to hold a leveling rob to take measurements.
• Sketches are drawn freehand
• Stationing is measured from the starting point.
• Surveying determines a position on Earth by making measurments
• Systematic errors have the same magnitude sign
• Tabulations conveys required information
• Tachymetry obtains distance with optical means
• Technician operates fieldwork instruments
• Theodolite acts similar to transit, but is more accurate
• Three-wire leveling is more accurate by determining three horizontal points rather than a single one.
• Topographic Surveys define ground and elevation
• Total station is a theodolite for angle, distance and coordinate measurements
• Transit measures angles, distances and elevation
• Traverse connects lines with lengths and directions
• Traverse connect lines with direct stations
• Traversing locates a position by measuring lengths and directions
• Triangulation measures angles using control points
• Trigonometric/Indirect Leveling measures difference through angles
• Trilateration measures triangles using electronic lengths
• True meridian passes through poles and the observer’s position.
• Turning point is where foresight and backsight rod readings enable a leveling operation to continue.

Terms Ending

• Utility men provide assistance
• Vertical control is provided by benchmarks
• Vertical datum has positions with respect to the mean sea level
• Weights indicate precision in a set