**Namespace: **
FDF.Common.CoordinateSystems

**Assembly: **FDF.Common (in FDF.Common.dll)

# Syntax

Visual Basic (Declaration) |
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Public Enum CrsCoodinateReferenceSystemType |

C# |
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public enum CrsCoodinateReferenceSystemType |

C++ |
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public enum class CrsCoodinateReferenceSystemType |

J# |
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public enum CrsCoodinateReferenceSystemType |

JScript |
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public enum CrsCoodinateReferenceSystemType |

# Members

Description | |
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Compound | In historic geodetic practice, horizontal and vertical positions were determined independently. It is established practice to combine the horizontal coordinates of a point with a height or depth from a different coordinate reference system. This has resulted in coordinate reference systems that are horizontal (2D) and vertical (1D) in nature, as opposed to truly 3-dimensional. The coordinate reference system to which these 2D+1D coordinates are referenced combines the separate horizontal and vertical coordinate reference systems of the horizontal and vertical coordinates. Such a system is called a compound coordinate reference system (CCRS). It consists of a non-repeating sequence of two or more single coordinate reference systems. The coordinate order within a coordinate tuple for a compound CRS is the sequence of the component single CRSs and then the sequence of coordinates for the coordinate tuples for each of those component single CRSs. |

Engineering | A coordinate reference system that is used only in a contextually local sense. This sub-type is used to model two broad categories of local coordinate reference systems: a) earth-fixed systems, applied to engineering activities on or near the surface of the earth; b) coordinates on moving platforms such as road vehicles, vessels or aircraft. Earth-fixed Engineering CRSs are commonly based on a simple flat-earth approximation of the earth's surface, and the effect of earth curvature on feature geometry is ignored: calculations on coordinates use simple plane arithmetic without any corrections for earth curvature. The application of such Engineering CRSs to relatively small areas and "contextually local" is in this case equivalent to "spatially local". |

Geocentric | A coordinate reference system that deals with the earth's curvature by taking the 3D spatial view, which obviates the need to model the earth's curvature. The origin of a geocentric CRS is at the approximate centre of mass of the earth. |

Geographic2D | A coordinate reference system based on an ellipsoidal (including spherical) model of the earth. This provides an accurate representation of the geometry of geographic features for a large portion of the earth's surface. Used when positions of features are described on the surface of the ellipsoid through latitude and longitude coordinates |

Geographic3D | A coordinate reference system based on an ellipsoidal (including spherical) model of the earth. This provides an accurate representation of the geometry of geographic features for a large portion of the earth's surface. Used when positions are described on, above or below the ellipsoid and includes height above the ellipsoid. These ellipsoidal heights (h) cannot exist independently, but only as an inseparable part of a 3D coordinate tuple defined in a geographic 3D coordinate reference system. Thus ellipsoidal heights cannot be referenced to a vertical coordinate reference system. |

Projected | A coordinate reference system that is based on an approximation of the shape of the earth's surface by a plane. The distortion that is inherent to the approximation is carefully controlled and known. Distortion correction is commonly applied to calculated bearings and distances to produce values that are a close match to actual field values. A Projected CRS is derived from a Geographic 2D CRS. One geographic CRS may serve as the base for many projected CRSs. |

Vertical | A coordinate reference system which makes use of the direction of gravity to define the concepts of height (H) or depth. The relationship with gravity may be complex. |