Coordinate systems Flashcards
coordinate space
agreed upon range of coordinates used to portray features
map units
units used for measurement to create coordinates, must be consistent through all features
coordinate systems
coordinate space whose characteristics are defined and established according to cartographic standards and tied to a specific location
geographic coordinate systems GCS
longitude and latitude
universal transverse Mercator UTM
coordinate system of meters
state plane coordinate system
system of feet
latitude
vertical angle above or below the equator +-90 degrees
longitude
horizontal angles east to west of the prime meridian +-180 degrees
datum
an approximation of longitude and latitude coordinates to meet specific mapping needs, based on a spheroid and geoid
transformation
converting between datums which can introduce error
map projections
converting locations on a globe to a flat map converted from a GCS
cylindrical projections
uses a cylindrical surface that touches the earth at the equator
transverse projections
cylinder touches a line of longitude
oblique projection
touches the earth at an angle
conic projection
sets a cone on the sphere touching the earth in one or 2 locations at a standard parallel
azimuthal projections
a plane tangent or secant to the sphere used to display poles
parameters
properties used to customize the projection for a geographic area and purpose via a central meridian (x=0), a latitude of origin (y=0), standard parallels, and false northing or easting
GCS projection
not really projected, highly distorted, used to distribute data
UTM projection
based on a secant transverse cylindrical projection in 60 zones around the world with negligible distortion in the zone
state plane projections
assortment of projections for large scale mapping in the US using 3 different projections to minimize distortion
state and national grids
individually defined coordinate systems or projections for specific areas
display units
units selected by the user different from the map units
spatial reference
includes the coordinate system, the x-y domain, and the resolution
resolution
represents underlying accuracy of x-y values
project tool
converts data from different coordinate systems to the official one
geodesy
modern science of measuring the surface of the earth and exact position of location
equal area projections
maintain area but distort shape and direction
conformal projections
maintain shape but distort area and distance
equidistant projections
maintain proportional distance from a center point but area shape and direction are distorted
compromise projections
reduce all distortions but preserve none
