CA Projection
All maps in this series are represented in the Albers Equal Area Projection. This information is included in the header file of each geotiff image. The following is the standard text representation of the geotiff header:
Example 1. Geotiff Header Information
For California Teale Albers, NAD27 projection:
Geotiff_Information:
Version: 1
Key_Revision: 1.2
Tagged_Information:
End_Of_Tags.
Keyed_Information:
GTModelTypeGeoKey (Short,1): ModelTypeProjected
GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
ProjCoordTransGeoKey (Short,1): CT_AlbersEqualArea
ProjectionGeoKey (Short,1): User-Defined
GeogGeodeticDatumGeoKey (Short,1): Datum_North_American_Datum_1927
GeogEllipsoidGeoKey (Short,1): Ellipse_Clarke_1866
ProjNatOriginLongGeoKey (Double,1): -120
ProjNatOriginLatGeoKey (Double,1): 0
ProjFalseEastingGeoKey (Double,1): 0
ProjFalseNorthingGeoKey (Double,1): -4000000
ProjStdParallel1GeoKey (Double,1): 34
ProjStdParallel2GeoKey (Double,1): 40.5
PCSCitationGeoKey (Ascii,38): "Albers Equal Area North American 1927"
ProjectedCSTypeGeoKey (Short,1): User-Defined
ProjLinearUnitsGeoKey (Short,1): Linear_Meter
End_Of_Keys.
End_Of_Geotiff.
For California Teale Albers, NAD83 projection:
Geotiff_Information:
Version: 1
Key_Revision: 1.2
Tagged_Information:
End_Of_Tags.
Keyed_Information:
GTModelTypeGeoKey (Short,1): ModelTypeProjected
GTRasterTypeGeoKey (Short,1): RasterPixelIsPoint
GeographicTypeGeoKey (Short,1): GCS_NAD83
ProjectedCSTypeGeoKey (Short,1): User-Defined
ProjectionGeoKey (Short,1): User-Defined
ProjCoordTransGeoKey (Short,1): CT_AlbersEqualArea
ProjLinearUnitsGeoKey (Short,1): Linear_Meter
ProjCenterLongGeoKey (Double,1): -120
ProjNatOriginLatGeoKey (Double,1): 0
ProjFalseEastingGeoKey (Double,1): 0
ProjFalseNorthingGeoKey (Double,1): -4000000
ProjStdParallel1GeoKey (Double,1): 34
ProjStdParallel2GeoKey (Double,1): 40.5
PCSCitationGeoKey (Ascii,38): "Albers Equal Area North American 1983"
ProjectedCSTypeGeoKey (Short,1): User-Defined
ProjLinearUnitsGeoKey (Short,1): Linear_Meter
End_Of_Keys.
End_Of_Geotiff.
The associated proj4 arguments are:
Example 2. Proj 4 parameters
For California Teale Albers, NAD27 projection:
+proj=aea
+lat_1=34.00
+lat_2=40.50
+lat_0=0.00
+lon_0=-120.00
+x_0=0.000
+y_0=-4000000.000
+ellps=clrk66
+units=m
For California Teale Albers, NAD83 projection:
+proj=aea
+lat_1=34.00
+lat_2=40.50
+lat_0=0.00
+lon_0=-120.00
+x_0=0.000
+y_0=-4000000.000
+ellps=GRS80
+units=m
+datum=NAD83
The corner coordinates vary with each individual map.
The OpenGIS WKS representation of this projection is:
Example 3. OpenGIS WKS Projectioin Information
For California Teale Albers, NAD27 projection:
PROJCS["Custom",
GEOGCS["GCS_North_American_1927",
DATUM["D_North_American_1927",
SPHEROID["Clarke_1866",6378206.4,294.9786982]],
PRIMEM["Greenwich",0],
UNIT["Degree",0.0174532925199433]],
PROJECTION["Albers"],
PARAMETER["False_Easting",0],
PARAMETER["False_Northing",-4000000],
PARAMETER["Central_Meridian",-120],
PARAMETER["Standard_Parallel_1",34],
PARAMETER["Standard_Parallel_2",40.5],
UNIT["Meter",1]]
For California Teale Albers, NAD83 projection:
PROJCS["Custom",
GEOGCS["NAD83",
DATUM["North_American_Datum_1983",
SPHEROID["GRS 1980",6378137,298.257222101]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433]],
PROJECTION["Albers"],
PARAMETER["False_Easting",0],
PARAMETER["False_Northing",-4000000],
PARAMETER["Central_Meridian",-120],
PARAMETER["Standard_Parallel_1",34],
PARAMETER["Standard_Parallel_2",40.5],
UNIT["Meter",1]]
California
Home
