Metrological Glossary

  • Accuracy - qualitative concept of the conformity (or closeness) of a measurement to it's "true value."
  • As-built Survey - Post-construction survey created in order to confirm design execution and/or record in-progress revisions.
  • Azimuth - The angle to a line-of-sight measured clockwise, usually from a north meridian.
  • Backsight - A sight taken with a level to a point of known elevation, thus permitting the surveyor to compute the elevation of the "Height of the Instrument (HI). Also, a sight taken to a point of known position to establish a reference direction.
  • Baseline - A line of reference for survey work, usually the centerline of a road although any convenient arbitrary line can be used or established.
  • Benchmark - A fixed solid reference point with a precisely determined and published location.
  • Control Survey - A survey taken to establish reference points and elevations.
  • Data Collector - an electrronic fieldbook designed to store data fields, both measured and descriptive.
  • Datum - An assumed or fixed horizontal reference plane.
  • EDMI - Electronic Distance Measuring Device.
  • Elevation - The vertical distance above or below a given datum.
  • Geodetic Datum - A precisely established series of benchmarks referenced to adjust Mean Sea Level.
  • Global Positioning System (GPS) - A ground positioning (x,y,z) system based on the reception and analysis of NAVSTAR satellite signals.
  • Ground Distance - A distance as measured on the ground.
  • Hydrographic Survey - A survey designed to define shorelines and identify underwater features.
  • Latitude - Angular distance from the earths center measured northerly or southerly from the equatorial plane in units of degrees.
  • LiDAR - (Laser Direction & Ranging) a measuring system that uses laser light to detect and locate points based on the same principle as radar and in a similar fashion as a Total Station.
  • Longitude - Angular distance measured in the plane of the equator from the reference meridian through Greenwich England.
  • Meridian - A north-south reference line.
  • Mistake - A poor result due to carelessness or misunderstanding.
  • Monument - A permanent reference point for horizontal and vertical positioning.
  • Photogrammetry - the process of acquiring measurements and/or making surveys and maps through the use of photographs, esp. aerial photographs.
  • Point Cloud - Laser scan data (in the form of points with x-y-z and colour/intensity values) from a single or multiple scans in a defined volume space.
  • Precision - The degree of refinement with which a measurement is made.
  • Reference Control - The point of reference where all measurements will be tied to.
  • Registration (pointcloud) - The process of scaling, aligning and merging two or more point clouds into one.
  • Repeatability - Potential for the same results to be repeated over time. One of the measures in determining the accuracy of a technique, particular as part of a Daubert test.
  • Resolution - The smallest change in distance that a system is capable of detecting. It is not however, a measure of accuracy.
  • Scan Registration - The process by which Laser scans are tied to the reference or survey control.
  • Segmentation - Process of separating and isolating groups of points from a Scan Point Cloud.
  • Station - A point on a baseline a specified distance from a start point (identified as 0+00). 100 feet/meters are full stations while 2+45.20 describes a point 245.2 feet from the start point.
  • Total Station - A system combing an Electronic Distance Measurer (EDM), Theodolite and Data Collector for locating points relative to an established baseline (station point to backsight).
  • UTM - Universal Transverse Mercator Grid System.

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