Querying through the EPSG database, I can see the tables
epsg_coordoperation where transforms and conversions between different CRS are stored, and
epsg_coordoperationmethod which stores the mathematical methods used by the transformations. Correct me whether I'm wrong.
To make an example, looking through the details of the conversion form ED50 to WGS84 over Sicily (http://www.epsg-registry.org/, --> retrieve by code --> 1143), I can see that the transformation involves simple shifts on the 3 cartesian axis. Operation is ED50 to WGS84, operation method is Geocentric Translation.
My statements which I would like to be either confirmed or corrected are:
- coordinate operations are always meant to reach a target CRS;
- coordinate transformations involve a change of datum, e.g. [geocentric<-->geocentric] or [projected<-->projected], etc.
- ..as coordinate conversions do, but regarding a [projected<-->geographic] error-free translation;
- one could apply arbitrary operation methods to a georeferenced dataset, say a simple arbitrary shift on one or more dimensions in the most simple case, given that the requirementes are met.
Considering only the operation methods, does applying method X to CRS A always take to a different CRS? But which one? E.g. a Lambert Conic Conformal (2SP) - EPSG:9802 - projects ellipsoidal coordinated to a projected XY map, but to which CRS? Or again, a shift on an ED50-based image may take to a WGS84-based image, but only if the shifts are the ones defined in the correct operation (--> Parameter values).
Bob wants to reproject a coverage from a source to a target CRS. Are there cases in which he would prefer to specify its own path of CRS transform concatenation instead of the default method offered by foo library?
Thanks in advance for any effort.