Georeferencing parameters and transformations explained#78
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To the introduction, subsections are added describing map coordinates, geographic coordinates and datum, reference point, orientation, and scale. These are all made more concise by deferring any mention of the CRS, convergence, grivation, etc. The Georeferencing dialog section is simplified a little due to having explanations of terms moved to the introductory sections. The details of georeferencing calculation in this version gloss over the need for a CRS and the added complexity of compensating for the projected grid. The plan is to flesh out the missing details and move the section to after the CRS is introduced.
The calculation of latitude and longitude from map coordinates had been described loosely, without reference to the CRS. This is now refined to mention grivation and combined scale factor. It is moved to follow the description of CRS. The subsection covering calculation of real world size from map size is removed, subsumed as part of the precise calculation of latitude and longitude. A few fixes to the wording are included.
Adding technical terms needed for further explanation of georeferencing. Many of these are initialisms explained in the page where used. A few are common abbreviations for specific versions of international technical standards.
The main change for this commit is to add a description of calculation of latitude/longitude in general terms, without reference to a specific CRS. Next, CRS is introduced, along with details of how a CRS is used to make the latitude/longitude more deterministic, having the benefit of a projected grid. This change also includes several changes for clarity.
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As requested in comments on Mapper #2190 and Mapper #2499 this adds to the Georeferencing help page. It describes the parameters, coordinate systems, and transformations between coordinates independent of the Georeferencing dialog.
Edits or comments are welcome.