This spatial system is used to specify location, shape and orientation (LSO) of a feature or observation on or near the surface of earth based on a projected horizontal coordinate system and a vertical coordinate system.

A  projected horizontal coordinate system is a planar two dimensional approximation of the earth's surface. Unlike geographic horizontal coordinate systems, a planar coordinate system has constant length, angles, and areas across the two dimensions. I.e. calculations are done by simple geometrical computations.

Redbex allows you to define (almost) any projected coordinate system. The specification includes the definition of the Projection (the mathematical operation to project objects on the Earth's surface to a planar coordinate system), the linear unit for measuring distances and areas and the vertical coordinate system to be used for elevation values. See Table 1 for a summary of settings used to define a projected system.

In a projected system the LSO of a real world object can be approximated by geometries based on coordinates X and Y together with a reference to the used projected system. Additionally to this geometry an elevation value can be stored. This value is expressed in the vertical coordinate system that is used by this projected system.

Operations on geometries stored with a reference to a projected system use simple geometric computation to work out the result.  Note that - unless stated otherwise - the elevation is not used in operations done on geodetic geometries, i.e. all calculations are done as if the elevation was zero.

Additionally to the shape and the elevation value the Application Server allows to specify a height and a depth of a geometry. These values define the height above the given elevation value and the depth below the given elevation value and can be used for an approximation of the real world 3D shape. E.g. if the geometry describes position and shape of a house, the height extent can be used to specify the height of the house the depth value can be used to define the depth of the houses foundations. The Application Server does usually not use this information in any geometric calculations. Presentations might however use this information in 3D models.

In Redbex Projected systems are defined globally. Newly installed Application Server Databases include some some predefined projected systems. Some of these predefined systems may be protected and cannot be modified or deleted.

Table 1: Settings for a projected system