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342  Geospatial Reference Data (R)

       

Input Standards

Required if applicable/Required if applicable
1st Indicator  Geospatial reference dimension
Horizontal coordinate system
1 Vertical coordinate system
2nd Indicator  Geospatial reference method
Geographic
1 Map projection
2 Grid coordinate system
3 Local planar
4 Local
5 Geodetic model
6 Altitude
7 Method specified in ‡2
8 Depth
Subfields (R=Repeatable  NR=Nonrepeatable) Input Standards 
‡a Name (NR) Required if applicable/Required if applicable
‡b Coordinate or distance units (NR) Required if applicable/Required if applicable
‡c Latitude resolution (NR) Required if applicable/Required if applicable
‡d Longitude resolution (NR) Required if applicable/Required if applicable
‡e Standard parallel or oblique line latitude (R) Required if applicable/Required if applicable
‡f Oblique line longitude (R) Required if applicable/Required if applicable
‡g Longitude of central meridian or projection center (NR) Required if applicable/Required if applicable
‡h Latitude of projection center or projection origin (NR) Required if applicable/Required if applicable
‡i False easting (NR) Required if applicable/Required if applicable
‡j False northing (NR) Required if applicable/Required if applicable
‡k Scale factor (NR) Required if applicable/Required if applicable
‡l Height of perspective point above surface (NR) Required if applicable/Required if applicable
‡m Azimuthal angle (NR) Required if applicable/Required if applicable
‡n Azimuth measure point longitude or straight vertical longitude from pole (NR) Required if applicable/Required if applicable
‡o Landsat number and path number (NR) Required if applicable/Required if applicable
‡p Zone identifier (NR) Required if applicable/Required if applicable
‡q Ellipsoid name (NR) Required if applicable/Required if applicable
‡r Semi-major axis (NR) Required if applicable/Required if applicable
‡s Denominator of flattening ratio (NR) Required if applicable/Required if applicable
‡t Vertical resolution (NR) Required if applicable/Required if applicable
‡u Vertical encoding method (NR) Required if applicable/Required if applicable
‡v Local planar, local or other projection or grid description (NR) Required if applicable/Required if applicable
‡w Local planar or local georeference information (NR) Required if applicable/Required if applicable
‡2 Reference method used (NR) Required if applicable/Required if applicable




Definition

The frame of reference for the coordinates in a data set. Include enough information so that the user can identify how location accuracy has been affected through the application of a geospatial reference method, and can manipulate the data set to recover location accuracy. Use in conjunction with the Content Standards for Digital Geospatial Metadata available at the Federal Geographic Data Committee web site ( http://www.fgdc.gov/standards/standards_publications/).

Code the map projection in Proj (Projection).

Guidelines

 
Map projections 

Every flat map misrepresents the surface of the Earth in some way. A map or parts of a map can show one or more—but never all—of the following true directions: true distances; true areas; true shapes.

On an equidistant map, distances are true only along particular lines, such as those radiating from a single point selected as the center of the projection. Shapes are more or less distorted on every equal-area map. On conformal maps, sizes of areas are distorted even though shapes of small areas are shown correctly. The degree and kinds of distortion vary with the projection. Some projections are suited for mapping large areas that are mainly north-south in extent, others for large areas that are mainly east-west in extent, and still others for large areas that are oblique to the Equator.

Use the following subfields for the designated projection:

Projection Subfields
Albers conical equal area ‡a, ‡e, ‡g, ‡h, ‡i, ‡j
Azimuthal equidistant ‡a, ‡g, ‡h, ‡i, ‡j
Equidistant conic ‡a, ‡e, ‡g, ‡h, ‡i, ‡j
Equirectangular ‡a, ‡e, ‡g, ‡i, ‡j
General vertical near-sided perspective ‡a, ‡l, ‡g, ‡h, ‡i, ‡j
Gnomonic ‡a, ‡g, ‡h, ‡i, ‡j
Lambert azimuthal equal area ‡a, ‡g, ‡h, ‡i, ‡j
Lambert conformal conic ‡a, ‡e, ‡g, ‡h, ‡i, ‡j
Mercator ‡a, ‡e or ‡k , ‡g, ‡i, ‡j
Miller cylindrical ‡a, ‡g, ‡i, ‡j
Modified stereographic for Alaska ‡a, ‡i, ‡j, ‡a, ‡g, ‡i, ‡j
Oblique Mercator ‡a, ‡k, ‡m and ‡n or ‡e, ‡f , ‡e, ‡f, ‡h, ‡i, ‡j
Orthographic ‡a, ‡g, ‡h, ‡i, ‡j
Polar stereographic ‡a , ‡n , ‡e or ‡k , ‡i, ‡j
Polyconic ‡a, ‡g, ‡h, ‡i, ‡j
Robinson ‡a, ‡g, ‡i, ‡j
Sinusoidal ‡a, ‡g, ‡i, ‡j
Space oblique Mercator ‡a, ‡o, ‡i, ‡j
Stereographic ‡a, ‡g, ‡h, ‡i, ‡j
Transverse Mercator ‡a, ‡k, ‡g, ‡h, ‡i, ‡j
Van der Grinten ‡a, ‡g, ‡i, ‡j


Punctuation 

Omit punctuation at the end of the field unless the field ends with an abbreviation, initial/letter, or other data that requires punctuation.

1st Indicator

Geospatial reference dimension. Indicate a system which measures linear or angular quantities or a system which measures vertical distances (altitudes or depths).
 
Horizontal coordinate system. A system which measures linear or angular distances.
342 1 Polyconic ‡g 0.9996 ‡h 0 ‡i 500,000 ‡j 0
 
1 Vertical coordinate system. A system which measures vertical distances (altitudes or depths).
342 1 6 National geodetic vertical datum of 1929 ‡v 1 ‡b meters ‡w Implicit coordinates

2nd Indicator

Geospatial reference method.  Indicates the method used to identify the system.
 
Geographic. A coordinate system that defines the position of a point on the Earth's surface with respect to a reference spheroid.
342 ‡c 0.0004 ‡d 0.0004 ‡b Decimal degrees
 
1 Map projection. A systematic representation of all or part of the surface of the Earth on a plane.
342 1 Polyconic ‡g 0.9996 ‡h 0 ‡i 500,000 ‡j 0
 
2 Grid coordinate system. A plane-rectangular coordinate system usually based on, and mathematically adjusted to, a map projection so that geographic positions can be readily transformed to and from plane coordinates.
342 2 Universal transverse Mercator
 
3 Local planar. Any right-handed planar coordinate system of which the z-axis coincides with a plumb line through the origin that is aligned locally with the surface of the Earth.
342 3 North American datum of 1927
 
4 Local. Any coordinate system that is not aligned with the surface of the Earth.
 
5 Geodetic model. Parameters for the shape of the Earth.
342 5 ‡s World geodetic system 72 ‡t 6378135 ‡u 298.26
 
6 Altitude. A system which measures altitudes (elevations).
342 1 6 National geodetic vertical datum of 1929 ‡v 1 ‡b meters ‡w Implicit coordinates
 
7 Method specified in ‡2 . The geospatial reference method used.
 
8 Depth.  A system that measures depths.
342 1 8 Lowest astronomical tide

Subfields

 
‡a Name   Base content on the 2nd indicator value.
 
2nd indicator Use for
1 Name of a map projection
2 Grid coordinate system
5 Horizontal datum name (the system used for defining the coordinates of points)
6 Altitude datum name (the level surface from which altitudes are measured)
8 Depth datum name (the surface from which depths are measured


‡b Coordinate or distance units   Base content on the 2nd indicator value.
 
2nd indicator Use for
Geographic coordinate units (units of measure used for latitude and longitude values)
6 Altitude distance units (units in which altitudes are recorded)
8 Depth distance units (units in which depths are recorded)


342 1 6 National geodetic vertical datum of 1929 ‡v 1 ‡b meters ‡w Implicit coordinates
‡c Latitude resolution   The minimum difference between two adjacent latitude values expressed in geographic coordinate units of measure.
342 ‡c 0.0004 ‡d 0.0004 ‡b Decimal degrees
‡d Longitude resolution   The minimum difference between two adjacent longitude values expressed in geographic coordinate units of measure.
342 5 World Geodetic System 1984 (WGS-84) ‡c 0.0000001 ‡d 0.0000001 ‡b Degrees, Minutes, and Decimal seconds ‡q World Geodetic System 1984 (WGS-84) ‡r 6378137.0 ‡s 298.257223563
‡e Standard parallel or oblique line latitude   Use when 2nd indicator value is 1. Base content on subfield ‡a.
 
If subfield ‡a is Use for
Albers conical equal area, Equidistant conic, Equirectangular, Lambert conformal conic, Mercator, or Polar stereographic. Standard parallels (lines of constant latitude at which the surface of Earth and the place intersect)
Oblique Mercator. Oblique line latitudes (latitude of a point defining the line along which the projection is centered)


342 1 Lambert Conformal Conic ‡e 38.3 ‡e 39.45 ‡g -77 ‡h 37.8333 ‡i 800,000 ‡j 0
‡f Oblique line longitude   Longitudes of a point defining the line along which the Oblique Mercator projection is centered.
‡g Longitude of central meridian or projection center   Use when 2nd indicator value is 1. Base content on subfield ‡a.
 
If subfield ‡a is Use for
Albers conical equal area, Azimuthal equidistant, Equidistant conic, Equirectangular, Lambert conformal conic, Mercator, Miller cylindrical, Polyconic, Sinusoidal, Transverse Mercator or Van der Grinten. Longitude of the central meridian (the line of longitude at the center of a map projection)
General vertical near-sided projection, Gnomonic, Lambert azimuthal equal area, Orthographic, Robinson or Stereographic. Longitude of projection center (longitude of the point of projection for azimuthal projections)


342 1 Polyconic ‡g 0.9996 ‡h 0 ‡i 500,000 ‡j 0
‡h Latitude of projection center or projection origin   Use when 2nd indicator value is 1. Base content on subfield ‡a.
 
If subfield ‡a is Use for
General vertical near-sided projection, Gnomonic, Orthographic or Stereographic. Latitude of projection center (latitude of the point of projection for azimuthal projections)
Albers conical equal area, Azimuthal equidistant, Equidistant conic, Lambert conformal conic, Oblique Mercator, Polyconic or Transverse Mercator. Latitude of projection origin (latitude chosen as the origin of rectangular coordinates for a map projection)


342 2 Universal Transverse Mercator ‡p 13 ‡k 0.9996 ‡g -105.00 ‡h 0.00 ‡i 500,000 ‡j 0.0
‡i False easting   The value added to all x values in the rectangular coordinates for a map projection.
342 2 State Plane Coordinate System 27, Lambert Conformal Conic ‡p 0405 ‡g -69.0 ‡h 0.0 ‡i 500,000.0 ‡j 0.0
‡j False northing   The value added to all y values in the rectangular coordinates for a map projection.
342 1 Polyconic ‡g 0.9996 ‡h 0 ‡i 500,000 ‡j 0
‡k Scale factor   Use when the 1st indicator is 1. Base content on subfield ‡a.
 
If subfield ‡a is Use for
Mercator Equator (a multiplier for reducing a distance obtained from a map to the actual distance along the equator).
Oblique Mercator Center line (a multiplier for reducing a distance obtained from a map to the actual distance along the center line).
Transverse Mercator Central meridian (a multiplier for reducing a distance obtained from a map to the actual distance along the central meridian).
Polar stereographic The projection origin (a multiplier for reducing a distance obtained from a map to the actual distance at the projection origin).


342 1 2 Universal transverse Mercator ‡p 13 ‡k 0.9996 ‡g -105.00 ‡h 0.00 ‡i 500,000 ‡j 0.0
‡l Height of perspective point above surface   The height of the viewpoint above the Earth, expressed in meters, for the General vertical near-sided projection.
‡m Azimuthal angle   The angle measured clockwise from north and expressed in degrees when ‡a is Oblique Mercator.
‡n Azimuth measure point longitude or straight vertical longitude from pole   Base content on subfield ‡a.
 
If subfield ‡a is Use for
Oblique Mercator Azimuth measure point longitude (longitude of the map projection origin)
Polar stereographic Straight vertical longitude from pole (a longitude to be oriented straight up from the North or South Pole)


‡o Landsat number and path number  

The identification number of the Landsat satellite and the path number for the Space Oblique Mercator projection.

‡p Zone identifier   A zone identifier for the grid coordinate system identified in subfield ‡a.
342 2 State Plane Coordinate System 27, Lambert Conformal Conic ‡p 0405 ‡g -69.0 ‡h 0.0 ‡i 500,000.0 ‡j 0.0
‡q Ellipsoid name   An identification given to an established representation of the Earth's shape.
342 2 North American Datum of 1927 ‡q Clarke 1866 ‡r 6378206.4 ‡s 294.98
‡r Semi-major axis   The radius of the equatorial axis of the ellipsoid.
342 3 ‡v Missouri East State Plane NAD27 ‡q Clarke 1866 ‡r 6378206.4 M ‡s 294.97869821
‡s Denominator of flattening ratio   The denominator of the ratio of the difference between the equatorial and polar radii of the ellipsoid when the numerator is 1.
342 5 ‡s 294.98 ‡t 6378135 ‡u 298.26
‡t Vertical resolution   Base content on 2nd indicator value.
 
2nd indicator Use for
6 Altitude resolution (the minimum distance possible between two adjacent altitude values, expressed in altitude distance units of measure).
8 Depth resolution (the minimum distance possible between two adjacent depth values, expressed in depth distance units of measure).


342 6 ‡s 294.98 ‡t 6378135 ‡u 298.26
‡u Vertical encoding method   Base content on the 2nd indicator value.
 
2nd indicator Use for
6 Altitude encoding method.
8 Depth encoding method.


342 1 8 NGVD 1929 ‡t 0.01 ‡b feet ‡u Explicit depth coordinate included with horizontal coordinates
‡v Local planar, local or other projection or grid description   Base content on the 2nd indicator value.
 
2nd indicator Use for
1 Complete description for an undefined projection used for the data set. Include the name of the projection, the names of the parameters and values used for the data set, and the citation of the specification for the algorithms that describe the mathematical relationship between the Earth and the plane for the projection.
2 Complete description for an undefined grid system used for the data set. Include the name of the grid system, the names of the parameters and values used for the data set, and the citation of the specification for the algorithms that describe the mathematical relationship between the Earth and the coordinates of the grid system.
3 Description of a local planar system (any right-handed planar coordinate system of which the z-axis coincides with a plumb line through the origin that is aligned locally with the surface of the Earth).
4 Description of a local system (any coordinate system that is not aligned with the surface of the Earth and its orientation to the surface of the Earth).


‡w Local planar or local georeference information   Base content on the 2nd indicator value.
 
2nd indicator Use for
3 Local planar georeference information (a description of the information provided to register the local planar system to the Earth. For example, control points, satellite ephemeral data, inertial navigation data).
4 Local georeference information (a description of the information provided to register the local system to the Earth. For example control points, satellite ephemeral data, inertial navigation data).


‡2 Reference method used   Use when the 2nd indicator value is 7 for the geospatial reference method used in the data set.

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