Geographic Information Systems. Coordinate Systems. 1. Map Scale. A ratio between a distance on the map and the corresponding distance on the earth The distance on the map is always expressed as one, e.g., 1 : 100,000 Common map scales 1 : 24,000 1: 100,000 1 : 250,000
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The distance on the map is always expressed as one, e.g., 1 : 100,000
1 : 24,000
1 : 250,000
1 : 1,000,000
Which one is a larger map scale?
1 : 24,000 or 1 : 100,000
Basic elements of a coordinate system
location of every
other point can be
stated in terms of
Geographic coordinate system
UTM (Universal Transverse Mercator)
- great circles
- 43050’ W
system for the WORLD
Gerardus Mercator (1512-1594)
Courtesy of the Library of Congress, Rare Book Division, Lessing J. Rosenwald Collection.
and rarely use rows
44003’ Latitude N, 71058’ Longitude W = Zone ?
- Transverse Mercator for states of N-S extent
- Lambert's conformal conic projection for states of E-W extent
UTM and many other coordinate systems are defined based on the geographic coordinate system
- Graphical representation of the shape and horizontal location of physical features of land and other physical entities.
- identity elevation of the land in contour lines.
North American Datum of 1927 (NAD27) North American Datum of 1983 (NAD83)
On NAD83: -117 12 57.75961, 34 01 43.77884
On NAD27: -117 12 54.61539, 34 01 43.72995
- Map projections define how positions on the earth’s curved surface are transformed onto a flat map surface
- Coordinate systems superimposed on the surface to provide a referencing framework on which positions are measured
Cylindrical, Azimuthal, and Conic
Conformal, Equal-area, Equidistant, and Azimuthal
1. Mercator 2. Transverse Mercator
courtesy: Mary Ruvane, http://ils.unc.edu/