Map Projections

For ICON Engineering

http://bl.ocks.org/mbostock/raw/3711652/

State Plane Coordinate System

Utilizes Lambert Conformal Conic projection
Two standard parallels where cone intersects sphere
Scale decreases between parallels, increases outside

Lambert Conformal Conic

Conformal projection

Angles are preserved

Conic projection

Scale (distance) preserved at the standard parallels

Colorado State Plane Central

PROJCS["NAD_1983_HARN_StatePlane_Colorado_Central_FIPS_0502_Feet",
GEOGCS["GCS_North_American_1983_HARN",
DATUM["D_North_American_1983_HARN",
SPHEROID["GRS_1980",6378137.0,298.257222101]],
PRIMEM["Greenwich",0.0],
UNIT["Degree",0.0174532925199433]],

PROJECTION["Lambert_Conformal_Conic"],
PARAMETER["False_Easting",3000000.000316083],
PARAMETER["False_Northing",999999.999996],
PARAMETER["Central_Meridian",-105.5],
PARAMETER["Standard_Parallel_1",38.45],
PARAMETER["Standard_Parallel_2",39.75],
PARAMETER["Latitude_Of_Origin",37.83333333333334],
UNIT["Foot_US",0.3048006096012192]]

Components of the .prj file:

Name and Geoid data

Parameters unique to Colorado State Plane Central

Coordinates

Projecting vs Defining Projection

Projecting data is mathematically changing coordinates from one projection to another

Defining a projection is letting the GIS know which projection the data is in currently

If coordinate system is unknown, it must be defined. You can determine which projection it is in by checking its feature extents in ArcCatalog

Standard Projections Used at ICON

NAD83 HARN/Colorado State Plane North (us feet): EPSG 2876

NAD83 HARN/Colorado State Plane Central (us feet): EPSG 2877

NAD83 HARN/Colorado State Plane South (us feet): EPSG 2878

NAD83/UTM Zone 13 North: EPSG 26913