Understanding Coordinates. NJDEP & ESRI: Understanding Map Projections & Coordinate Systems. Department Standards. Spheroid GRS80 Datum NAD83 Projection New Jersey State Plane (based on Transverse Mercator) Units Feet . Parameters for Mapping.
ESRI: Understanding Map Projections & Coordinate Systems
A mathematical model of the earth must be selected.
Simplistic - A round ball having a radius big enough to approximate the size of the earth.
Reality - Spinning planets bulge at the equator with reciprocal flattening at the poles. e.g.
A mathematical model must be related to real-world features.
North American Datum - 1927
North American Datum - 1983
Changes to the values of any datum parameters can result in changes to coordinate values of points.
If you have two different datums, in practive you have two different geographic coordinate systems.
World Geodetic System - 1984
The datum on which GPS coordinates are based and probably the most common datum for GIS data sets with global extent.
Latitude/Longitude Lines of latitude Longitude lines N or S of Equator E or W of Prime MeridianGraticules
Projection surface, intersect at the poles, and measure distances east and west of the prime meridian.
Real-world features must be projected with minimum distortion from a round earth to a flat map; and given a grid system of coordinates.
A map projection transforms latitude and longitude
locations to x,y coordinates.
Converting a sphere to a flat surface results in distortion.
Imagine capturing the world in a net. The net divides the larger earth into sections, all contained in squares of the same size. Suddenly order is imposed on chaos. Finally we have the means to describe a location as so many squares to the left, so many to the right, so many up, or so many down, and at last we have its number.
Any projected data that you add to ArcMap, or that you project within ArcMap, is associated with a projected coordinate system (PCS) in addition to its underlying Geographic Coordinate System (GCS).
Planar coordinate systems are based on Cartesian coordinates.
NJ State Plane Coordinates system with an origin, a unit of measure (map unit), and usually a false easting or false northing.
A comprehensive system for identifying locations and making measurements over most of the earth's surface.
StatePlane NJ FIPS 2900 (Feet).prj
Geographic Coordinate System to provide a common references system for
State Plane Coordinate System
Minutes and seconds are expressed as decimal values. Used to store digital coordinate information.
36 minutes = .60 degrees (36/60) 30 seconds = .00833 degrees (30/3600)
2. Add up the degrees to get the answer:
37° + .60° + .00833° = 37.60833 DD
Example coordinate is 37° 36' 30" (DMS)
LAT DD = Latd +(Latm/60)+(Lats.s/3600)
LONG DD = -(-Longd+(Longm/60)+(Longs.s/3600))
FREE Software FOR WINDOWS - Coordinate Conversion to provide a common references system for