Map Projection - Map projections*portray the curved surface...

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Unformatted text preview: Map projections *portray the curved surface of the Earth on a flat surface* mathematical transformation that take spherical coordinates (latitude and longitude) and transform them to an XY (planar) coordinate system. Things to remember about map projections: 1. There is no “best projection” 2. The process of projection always create distortion 3. Select map projection which has minimal distortion in study area 4. “No map can rival the globe in truly representing the surface of the entire earth” - USGS The Globe True directions True Distances True Shapes True Areas Geographic Latitude / Longitude Projection Plot of latitude and longitude degree coordinates as if they were Y and X coordinates. Scale True in degrees along the Equator or vertically along any meridian. Distortion Considerable distortion away from the Equator due to horizontal increase in longitude degrees. Usage Used to save digital maps in unprojected form. Meridian Parallel Origin of grid is where the prime meridian meets the equator Units are in DD (decimal degrees) or DMS (degrees minutes seconds) Four Types of Map Projections (based on properties that are preserved) 1. Conformal Projection (Scale) – preserves local shape;- the scale of a map at any point on the map is the same in any direction- meridians (lines of longitude) and parallels (lines of latitude) intersect at right angles- shape is preserved locally 1. Equidistant Projection ( Distance) – maintains consistency of scale for certain distances- portrays distances from the center of the projection to any other place on the map 1. Equivalent Projection (Equal area) – areas are in correct relative size- mapped areas have the same proportional relationship to the areas on the Earth that they represent 1. Azimuthal Projection (Direction) – retains certain accurate distances- preserves direction when azimuths (angles from a point on a line to another point) are portrayed correctly in all directions. 3 General Classes of Projection (based on projection surface) 1. Cylindrical Projection – projecting the sphere into a cylinder 2. Conic Projection – projecting the sphere into a cone 3. Azimuthal – sphere is projected into a plane Concept of False Easting and False Northing- The false easting and the false northing move the origin of the coordinate system to its SW corner - All points will fall within the NE quadrant and have positive values...
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  • Spring '08
  • Villanueva
  • Map projection, Geographic coordinate system, Universal Transverse Mercator coordinate system, standard parallels

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Map Projection - Map projections*portray the curved surface...

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