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.
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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
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.
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.
Planar coordinate systems are based on Cartesian coordinates.
A comprehensive system for identifying locations and making measurements over most of the earth's surface.
StatePlane NJ FIPS 2900 (Feet).prj
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))