Shape File Specification

General Information

SURE will try to interpret all input shape types as 2D or 3D Polygons internally. Therefore it may have to do certain modifications to the input shapes to obtain correct Polygons.

This means all geometries of the following wkbGeometryTypes are internally stored as 2D or 3D Polygons:

  • wkbPolygon(ZM)
  • wkbMultiPolygon(ZM)
  • wkbLineString(ZM)
  • wkbMultiLineString(ZM)

General Specification

Shape Files that are passed to SURE must follow a certain specification that will be defined here:

  • Shape Files must contain exactly one layer, this one layer may contain multiple geometries of the types listed above
  • Shape Files may not contain curved geometries
  • Shape Files must be in the same coordinate system as the SURE project - if one or both of the coordinate systems is local, SURE will print a warning

Additionally SURE may have to do certain modifications before being able to work with a provided Shape File:

  • If the Shape File contains non-closed geometries, SURE will connect the last point with the first one - if this leads to an invalid polygon SURE will issue an error
  • If the Shape File contains geometries which have counter-clockwise outer rings, SURE will invert the winding order of the outer ring
  • If the Shape File contains geometries which have clockwise inner rings, SURE will invert their winding order
  • If the Shape File contains geometries that are tagged as curved geometries but only contain linear geometries and can thus be losslessly converted to linear geometries, SURE will do so

Area Shape Files

In order for SURE to work with Area Shape Files it may have to do additional modifications to the ones listed above: 

  • If the Area Shape File contains 3D geometries SURE will convert them to 2D geometries by ignoring the Z-component
  • If the Area Shape File contains geometries that touch or overlap, SURE will create the union of those geometries

Water Body Shape Files

Additional to the general rules for Shape Files Water Body Shape Files are expected to follow this set of rules: 

  • Water Body Shape Files must be 3D Shape Files - the Z-component is used exclusively for the interpolation during the creation of new points within the polygon
  • Water Body Shape Files projected onto the ground plane should be disjoint - if they touch or overlap, combining the Z-Values can lead to artifacts. In order to reduce the impact of these artifacts, assign corresponding height values to vertices of two polygons in the overlapping area.