Enumeration ReferenceType

A cartesian reference that can be used as a model reference or world reference.

This reference can be used to specify any non geospatial 2D X/Y plane or 3D X/Y/Z volume.

An geocentric reference is an reference based on a geodetic datum. Coordinates are expressed in (x,y,z) with regard to the center of the ellipsoid on which the geodetic datum is based. See the developers guide for a more elaborate explanation on geocentric references.

A geodetic reference system is a reference based on a geodetic datum. (x,y,z) coordinates in these references correspond with longitude, latitude and height values, respectively. Longitude and latitude values should be expressed in degrees, height values in meters. The developers guide contains a paragraph explaining the basics of geodetic references.

An grid reference is an reference that contains the relation between (longitude,latitude, height) coordinates and cartesian (x, y, z) coordinates. (x, y) is a regional Easting-Northing pair while z is equal to the original height.

• The Easting coordinate (x) is positive for East and negative for West.
• The Northing coordinate (y) is positive for North and negative for South.

A topocentric reference is a geocentric reference that is defined by a geodetic datum and a lon-lat-height point that defines the origin of the topocentric coordinate system of this reference.

A topocentric coordinate system is a right-handed cartesian coordinate system with the following properties:

• Its origin is defined by a lon-lat-height point on the ellipsoid.
• The y-axis is directed northwards and aligned to intersect with the polar rotational axis of the ellipsoid.
• The x-axis if directed eastwards.
• The x-y plane is tangential to the ellipsoid at the origin.
• The z-axis is perpendicular to the ellipsoid at the origin, and points outwards. In other words, the z-axis is perpendicular to the x-y plane.

This reference is also referred as an ENU (East-North-Up) projection.