Coordinate Systems
Georeferencing System:
o
Once we agree on the size and shape of the Earth, we can develop measurement
systems. The two important measurement systems are:
Geographic Coordinate Systems:
Latitude/Longitude angular measurements for an ellipsoidal earth
Cartesian Coordinate System:
X, Y (easting, northing) distance measurement systems for a flat earth
Earth Coordinate Geometry
o
The locations of any objects can be precisely determined with coordinate systems
developed based on
earth
and
plane
coordinate geometry
o
Earth coordinate system:
Longitude latitude (in decimal degrees)
Degrees, minutes, seconds
o
Determining locations on the earth is based on sexagesimal (1
o
=60’ , 1’=60”) scale. That
is, a circle is 360 degrees, each degree into 60 minutes, and each minute into 60 seconds
Earth Coordinate Geometry:
o
Lines that measure position north/south are called parallels:
Parallels:
Are of differing length – shorter away from the equator
Are parallel to one another
Are nearly equally spaced
Range from 0
0
– 90
0
(N: + , S: -)
o
Lines that measure position east/west are called meridians:
Meridians:
Are equal in length
Are spaced widest at the equator with convergence to the points of the
poles
Range from 0
0
– 180
0
(E: + , W: -)
Latitude
: is the location on the earth’s surface between the equator and either the North or the
South pole
The angle for a point is equal to the angle between the equator and the radius from the earth
center to the point on the surface
An imaginary plane is passed through a point and parallel to the equatorial plane, this will
intersect the Earth surface and form a parallel of latitude
Latitude
is represented with degree, minute, and seconds, labeled with a capital N or S, that is,
the positional north or south of the equator
o
For
example: 45
0
30’30”

Longitude
: using the same sexagesimal system as latitude, measures location
east (+) or west (-)
of the prime meridian that has
0 degree of longitude.
The maximum of longitude is 180 degrees
W or E.

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- Fall '18
- Geodesy, Geographic coordinate system, Earth Coordinate Geometry