Geodetic Framework – software architecture

Software architecture

Software architecture also influences geo-spatial computations and is particularly relevant with coordinate operations of type: Transformation.  Examples include the recognition of the sign convention applied within a specific algorithm or the adoption of early versus late binding techniques.

The first problem can be highlighted with respect to the treatment of Position Vector transformation versus the Coordinate Frame rotation where the sign convention used on the rotation parameters are equal but opposite.  Are both conventions recognized by the application or is the user expected to reverse the signs are part of the transformation definition?  Furthermore, it is important to ensure that the Source and Target CRS’ are correctly identified so as not to reverse the coordinate operation.

The second issue highlights whether the coordinate transformation (operation type and parameters) are included within the definition of a 2D geographical CRS or whether the coordinate transformation operations are recognized as independent entities within the inventory.  When defined within the 2D geographical CRS definition this is known as early binding.  When the model can be assigned to a coordinate transformation operation (between source and target CRS) independent of the CRS definition it is known as late binding.  Both techniques have their pros and cons, but the late binding is slightly favored as it offers higher flexibility and reduces the number of early binding CRS’ defined within the inventory.


Return to Our Philosophy