Map Projections GIS-101 Summer 2006 Semester

Important Things to Remember about Map Projections An attempt to take location information from a spheriod object and transfer to a flat surface As such, ALL projections are a distortion of the real world to some extent!

Attributes of Distortion Shape Size Distance Direction Area

Map Projections versus Coordinate Systems REMEMBER: Map Projections and Coordinate Systems are two different things!

Factors Associated with Map Projections Scale Map Units Projection Coordinate System Datum

Map Scale vs Spatial Scale 1:24,000 is a LARGER scale than 1:100,000 e.g. 1/24,000 is a larger number than 1/100,000 However, 1:24,000 however covers a smaller spatial scale than 1:100,000 (i.e. less area covered on a same sized map)

Topographic Mapping System

Examples of Projections Robinson Lambert Conformal Conic Mercator Transverse Mercator

Types or “Families” of Map Projections Cylindrical Conic Azimuthal or Planar

Orthographic Projection

Lambert Conformal Conic

Azimuthal Projection

Transverse Mercator

Mercator Projection

Examples of Coordinate Systems Latitude and Longitude (Geographic) Universal Transverse Mercator State Plane

Geographic Coordinate System Latitude & Longitude NOT a true “Projection”

Latitude / Longitude for US

UTM Grid Uses Transverse Mercator projection Units usually in meters 60 Zones 6 degrees per zone “N” or “S” Example:

UTM Coordinate System (US)

UTM Coordinate System

State Plane Uses either Lambert Conformal Conic (East- West States) OR Transverse Mercator (North-South States) Projections Units usually in feet

State Plane Coordinate System

Township & Range System