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Spatial Data in WATERS


EPA Office of Water geospatial and tabular data are hosted in a variety of formats including enterprise relational databases, web mapping servers and file-based storage.

Spatial Reference Systems used in WATERS

The majority of Office of Water spatial data is stored in the federal standard geodetic NAD83 coordinate system having the following parameters:

Angular Unit: Degree (0.01745329251994328)
Prime Meridian: Greenwich (0.000000000000000000)
Datum: North_American_Datum_1983
  Spheroid: Geodetic Reference System of 1980
    Semimajor Axis: 6378137.000000000000000000
    Semiminor Axis: 6356752.314140356100000000
    Inverse Flattening: 298.257222101

This spatial reference system is defined in the EPSG Geodetic Parameter Dataset Exit EPA Disclaimer with the numeric id of 4269.  Depending on the geographic information system several synonyms and equivalencies are utilized:

  • Oracle Spatial: Exit EPA Disclaimer
    Oracle Spatial defines geospatial information as its native MDSYS.SDO_GEOMETRY object. Each object has an SDO_SRID attribute value indicating the spatial reference system used. When storing NAD83 geodetic information in Oracle, WATERS uses SDO_SRID 8265 which is described by Oracle Corporation as "Longitude / Latitude (NAD 83)". 
     
  • ESRI ArcGIS Exit EPA Disclaimer
    ArcGIS describes geospatial information using named coordinate systems. When storing NAD83 geodetic information in ESRI products, WATERS uses the stock "NAD 1983" coordinate system. In older version of ESRI software this may be displayed as "GCS_North_American_1983". 
     
  • Safe Software FME Exit EPA Disclaimer
    FME describes geospatial information using named coordinate systems. When storing or transforming NAD83 geodetic information using FME, WATERS uses the stock "LL-83: NAD83 Latitude/Longitude, Degrees" coordinate system identifier. 
      
  • PostGIS Spatial and Geographic Objects for PostgreSQL Exit EPA Disclaimer
    PostGIS defines geospatial information using numeric spatial reference identifiers. When storing or transforming NAD83 geodetic information using PostGIS, WATERS uses SRID 4269.
     
  • Other Geographic Information Systems
    Most other GIS software and mapping servers reference NAD83 geodetic coordinate system as either EPSG SRID 4269 or via urn-notation as "urn:ogc:def:crs:OGC::CRS83".

Measurements in WATERS datasets

While features are stored as NAD83 geodetic data, when length and area are calculated EPA Office of Water follows the common approach of measuring geometries in an Albers Equal-Area Conic projection having the following parameters:

  • Continental United States:
    Projection: Albers Equal Area
    Datum: NAD 1983
    False_Easting: 0.0
    False_Northing: 0.0
    Central_Meridian: -96.0
    Standard_Parallel_1: 29.5
    Standard_Parallel_2: 45.5
    Latitude_Of_Origin: 23.0
    Linear Unit: Meter (1.0)


    Geographic Information System SRS Information:

    • EPSG: 5070
    • Oracle: 5070 added with 12c, otherwise use custom SRS 
    • ESRI: "NAD_1983_Contiguous_USA_Albers"
    • FME: None, custom SRS required
    • PostGIS: None, custom SRS required
  • Hawaii:
    Projection: Albers Equal Area
    Datum: NAD 1983
    False_Easting: 0.0
    False_Northing: 0.0
    Central_Meridian: -157.0
    Standard_Parallel_1: 8.0
    Standard_Parallel_2: 18.0
    Latitude_Of_Origin: 3.0
    Linear Unit: Meter (1.0)


    Geographic Information System SRS Information:

    • EPSG: None
    • Oracle: None, custom SRS required
    • ESRI: None, custom SRS required
    • FME: None, custom SRS required
    • PostGIS: None, Custom SRS required
  • Alaska:
    Projection: Albers Equal Area
    Datum: NAD 1983
    False_Easting: 0.0
    False_Northing: 0.0
    Central_Meridian: -154.0
    Standard_Parallel_1: 55.0
    Standard_Parallel_2: 65.0
    Latitude_Of_Origin: 50.0
    Linear Unit: Meter (1.0)


    Geographic Information System SRS Information:

    • EPSG: None
    • Oracle: None, custom SRS required
    • ESRI: "NAD_1983_Alaska_Albers"
    • FME: None, custom SRS required
    • PostGIS: None, custom SRS required
  • Puerto Rico/US Virgin Islands:
    Projection: Albers Equal Area
    Datum: NAD 1983
    False_Easting: 0.0
    False_Northing: 0.0
    Central_Meridian: -66.0
    Standard_Parallel_1: 8.0
    Standard_Parallel_2: 18.0
    Latitude_Of_Origin: 3.0
    Linear Unit: Meter (1.0)


    Geographic Information System SRS Information:

    • EPSG: None
    • Oracle: None, custom SRS required
    • ESRI: None, custom SRS required
    • FME: None, custom SRS required
    • PostGIS: None, custom SRS required
  • Pacific Trust Territories:
    Projection: Albers Equal Area
    Datum: NAD 1983
    False_Easting: 0.0
    False_Northing: 0.0
    Central_Meridian: 145.0
    Standard_Parallel_1: 8.0
    Standard_Parallel_2: 18.0
    Latitude_Of_Origin: 3.0
    Linear Unit: Meter (1.0)


    Geographic Information System SRS Information:

    • EPSG: None
    • Oracle: None, custom SRS required
    • ESRI: None, custom SRS required
    • FME: None, custom SRS required
    • PostGIS: None, custom SRS required

Adding Custom Coordinate Reference Systems

Support for these Albers Equal-Area Conic projections in commercial and open source GIS software is limited as these projections have only slowly been registered with the EPSG Geodetic Parameter Dataset Exit EPA Disclaimer. Below are instructions for adding these projections to your GIS.

  • Oracle Spatial

    Oracle users will need to add custom coordinate references to their installation of Oracle Spatial (MDSYS). This action will require administrative privileges on the Oracle database instance. Executing the script adds five custom projections, five custom transformation operations, and six operation parameters for each custom transformation to your Oracle Spatial coordinate system tables. We assume that SRIDs 1000001 through 1000005 are free and custom operation ids 100001 through 100005 are free. If you have preexisting custom projections and/or operations in that range you will need to adjust these ids accordingly.

    At the end you will have five new custom projection SRIDs available:

    • 1000001 - NAD83 Continental US Albers Equal Area USGS
    • 1000002 - NAD83 Hawaii Albers Equal Area USGS
    • 1000003 - NAD83 Alaska Albers Equal Area USGS
    • 1000004 - NAD83 Puerto Rico/Virgin Islands Albers Equal Area USGS
    • 1000005 - NAD83 Pacific Trust Albers Equal Area USGS
       

     
  • ESRI ArcGIS

    ESRI ArcGIS as of version 10.1 only provides stock coordinate reference systems for the continental United States and Alaska. In order to work with geospatial data in other US exclaves, users will need to add custom projections. The easiest way to do so is to copy the well known text definition below into a text file and save with the extension ".prj". Then within ArcCatalog simply import the file into your list of custom projections.

    NAD83 Hawaii Albers Equal Area USGS.prj
     
    NAD83 Puerto Rico Virgin Islands Albers Equal Area USGS.prj
     
    NAD83 Pacific Trust Albers Equal Area USGS.prj
     
  • Safe Software FME

    FME as of version 2013 does not provide definitions for these projections. Users may add the projections to FME by editing their MyCoordSysDefs.fme file as detailed here Exit EPA Disclaimer. Inserting the following text and restarting FME will allow users to work with all five projections.


     
  • PostGIS Spatial and Geographic Objects for PostgreSQL  

    PostGIS as of version 2.1.1 does not provide definitions for these projections.  Users will need to add five entries to their public.spatial_ref_sys table.  As only the projection for the continental United States has an existing EPSG identifier, four custom SRIDs will need to be defined for the remaining projections.  We assume that SRIDs 990002 through 990005 are free.  If you have preexisting custom projections in that range you will need to adjust these ids accordingly. At the end you will have five new SRIDs available:

    • 5070     - NAD83 Continental US Albers Equal Area USGS
    • 990002 - NAD83 Hawaii Albers Equal Area USGS
    • 990003 - NAD83 Alaska Albers Equal Area USGS
    • 990004 - NAD83 Puerto Rico/Virgin Islands Albers Equal Area USGS
    • 990005 - NAD83 Pacific Trust Albers Equal Area USGS
       

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