Remove Conversion sub-types

[desruisseaux]

GeoAPI defines some sub-types of ISO 19111 Conversion type:

• Projection
  • ConicProjection
  • CylindricalProjection
  • PlanarProjection

Those types were introduced at user requests for helping to identify map projection properties. They are not part of ISO 19111. However above list of types is only one classification among other possibilities (another possible classification would be whether the projection is conformal, equal-area, etc.).

We propose to deprecate in GeoAPI 3.1, and remove in GeoAPI 4.0, those non-standard types. We are not aware of any use in GeoAPI implementations (PROJ-JNI, Apache SIS…). If we want to provide this information, a better alternative may be to take inspiration from existing studies. For example:

• Compatibility Study between ISO 18026 CD, Spatial Reference Model (SRM) and ISO 19111, Geographic information – Spatial referencing by coordinates

Above study suggests that at least one other standards uses a code list with the following elements:

• orthogonal
• not orthogonal
• orthonormal
• not orthonormal
• conformal
• not conformal

[desruisseaux]

Done in 43ce2af58248931a53ec9f8bb58e83fcb2d8c876 followed by 1dd682e1b3950d7024b17f6639673b896f701441. The merges on the 3.1 branch keep those interfaces as deprecated.