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Concept of type and subtype

by Joaquin Jose del Cerro Murciano last modified 2010-09-06 16:14

Before seeing how to create a new geometry is necessary to understand the type and subtype concept. Depending on the geometric characteristics, a geometry will be of one type or other. Some types defined on gvSIG are:

  • Point: for geometries of point type.
  • Curve: for geometries of line type.
  • Surface: for geometries of polygon type.
  • Arc: for geometries of arc type.
  • etc.

All the types gvSIG supports currently are in TYPES in code form. If at any time somebody needs to create a new geometry that don't use any type on the list, he must contact with the gvSIG's team to assign a new code to the type, because it must be unique.

The type only refers to the type of the geomatic object, but it doesn't specify if geometry is on 2 or 3 dimensions, or if it supports M coordinate or not. For that, it's created the subtype concept, to indicate the geometry dimension. The gvSIG's subtypes are in SUBTYPES and it's the same than the types: if somebody wants to add a new subtype must contact with gvSIG's team to provide you a new code. In the next list we show several subtypes supported on gvSIG:

  • GEOM2D: 2-dimensional geometries.
  • GEOM2DZ: 2-dimensional geometries and value for coordenate Z.
  • GEOM3D: 3-dimensional geometries.
  • GEOM2DM: 2-dimensional geometries and M coordenate.
  • GEOM3DM: 3-dimensional geometries and M coordenate.

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