Chapter Two - Navigating Our World: Geodesy, Datums, and Coordinate Systems

Chapter Goals

 Define and explain classic geodesy Define and explain  modern geodesy precise global and regional locations, both horizontal and vertical (along the Earth and above the Earth), mapping the land sea, and ice, and determining the variations in the Earth’s gravitational pull and how this effects measurements Define and explain GNSS Define  topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." Define geoid Explain what a geoid is a model of how the model is made Explain why geoids are used in GIS and Cartography Define ellipsoid Define  spheroid a sphere-like 3D object where the radius in one direction is longer than the radius in a direction at a right angle to the first (ellipsoid of revolution) Define  reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid , global reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid , local reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid Explain when and why we use ellipsoids Explain when and why we use spheroids Define and explain Cartesian Coordinate Systems Define  geodetic datum the result of attaching a "free-floating" reference ellipsoid an ellipsoid that is drawn to best-fit an area. World reference ellipsoids are drawn to best-fit the entire geoid; local ellipsoids are best fit on one side to a single place of the geoid to a specifically measured geoid via control points and benchmarks. Explain how geodetic datums are made Define benchmark and control points Explain the similarities and difference between benchmarks Benchmarks are real-world locations which have been carefully surveyed with locations to match a specific geoid. and control points Define and explain horizontal and  vertical datums used to reference locations and distances above mean sea level; elevation. Define  orthometric height the measured distance between the geoid and the topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." . Define ellipsoid height Define  geoid separation the measured difference between the ellipsoid and the geoid Explain when we use orthometric height the measured distance between the geoid and the topographic surface a detailed map of the surface features of land. It includes the mountains, hills, creeks, and other bumps and lumps on a particular hunk of earth. The word is a Greek-rooted combo of topos meaning "place" and graphein "to write." . , ellipsoid height, and geoid separation the measured difference between the ellipsoid and the geoid Define and explain datum shifts, both major and minor Define Earth-centered, Earth-fixed Coordinate Systems Define and explain  geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. Explain where a geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. is drawn Thoroughly explain geographic coordinate systems (GCS) including the parts it's made up of, why it's used, and how it differs from a geographic grid the result of using an established angular unit of measure to label the intersections of north-south and east-west lines on the surface of the Earth starting the labels at a principal meridian the north-south line from which the labeling begins.  East-west lines have a very obvious start point: the equator.  North-south lines must start somewhere, so when it is established for a particular geographic grid, it can be considered the principal meridian. Define projected coordinate systems (PCS) Explain the advantages of PCS's Explain the disadvantages of PCS's  Define and explain distortion, naming the six kinds of distortion Define and explain  developable surface a geometric shape which will not be distorted when flattened.  Used as the base shape to transfer features during projections.  Most often a cone, cylinder, or plane (azimuthal) Name the three major developable surfaces Define and explain  projection technically: the result of using one of variety of methods to transfer the geographic locations of features from a geographic coordinate system to a developable surface everyday use: any coordinate system, geographic or projected aspect The direction the developable surface a geometric shape which will not be distorted when flattened.  Used as the base shape to transfer features during projections.  Most often a cone, cylinder, or plane (azimuthal) faces in relation to the geographic coordinate system. Normal; transverse, oblique Name the three major projection technically: the result of using one of variety of methods to transfer the geographic locations of features from a geographic coordinate system to a developable surface everyday use: any coordinate system, geographic or projected aspects Define and explain  projection technically: the result of using one of variety of methods to transfer the geographic locations of features from a geographic coordinate system to a developable surface everyday use: any coordinate system, geographic or projected method Explain the difference between a projection technically: the result of using one of variety of methods to transfer the geographic locations of features from a geographic coordinate system to a developable surface everyday use: any coordinate system, geographic or projected method and a PCS Define and explain the State Plane Coordinate System Define and explain the Universal Transverse Mercator (UTM) system Define  map scale a mathematical representation expressing distance on a map vs distance on the ground