datums and coordinates
DESCRIPTION
UTM System coordinate describtionTRANSCRIPT
Lat / Long Coordinate System
Latitude
Parallels of latitude
0° latitude
northlatitude
southlatitude
90°N
equator
Lat / Long Coordinate System
Longitude
West Longitude
Meridians of longitude0° longitudePrime Meridian
Eastlongitude
Grenwich, England
UTM Coordinate Systems
Allows projection of a spherical surface onto a flat surface
A plane coordinate system to relate the coordinates of points on earth’s curved surface with the coordinates of the same points on a plane or flat surface
UTM Zones in North America174180 168 162 156 150 144 138 132 126 120 114 108 102 96 90 78 72 54606684 48
Datum and Ellipsoids
• Datum - represented by ellipsoid
• Reference ellipsoid examples: • Clarke 1866• GRS 80• WGS 84
NAD27: Clarke 1866 ellipsoidorigin in Kansas
Datum Origin
on Surface of
Earth
Ellipsoid Model based on less precise surveys
NAD27: Leaving Behind • Invented Space Travel
• Increasing accuracy of surveys
• Shift from optical surveys to a mathematical model of the Earths shape
• The result is a specific point on the landscape can take on multiple meanings
GPS Datum: WGS 84
Origin is at the Earth’s center of mass (geocentric)
This is the datum used for the NAVSTAR GPS satellites
WGS84:WGS84 ellipsoidorigin center of earth
The origins of the WGS84 and NAD83 ellipsoids are at the center of the earth’s mass, which makes them ideal for a GPS datum
Datum Adjustments• Known as Datum Adjustments or Epochs
• WGS84 (G1150) – most current version
• “Original” NAD83 = NAD83 (1986)– NAD83 (1992)– NAD83 (2002)– ……
• Most Current NAD83– NAD83 (CORS96) (Epoch 2003.00)