The attached file isn't of a type recognized by my iPhone 13 or by my Windows 10 computer. Could you send a CSV, in PNEZD format, file? Thanks.
@field-dog It is a comma delimited text file. Open with Excel or Word. I just opened it up on my tablet with Google chrome.
Really, really good exercise for learning.
If we use Q-Cogo's Helmert transformation (what the math behind the others is, I have no clue) with its calculated scale factor and again with a scale factor = 1, we get this:
and this:
Why do transformed points 531 and 543 match their observed coordinates when the Scale Factor <> 1 but do not match their observed coordinates when the Scale Factor = 1? It's because a scale factor <> 1 preserves distances in the transformed file while a Scale Factor = 1 preserves distances in the input file.
In this case, the calculated distance from 531 to 543 is 1,073.743 ft while the calculated distance from 2 to 6 is 1,073.147 ft. It seems reasonable to conclude that the input file contains ground coordinates and the observed points are State Plane coordinates.
When the Scale Factor = 1, the underlying mathematics of the Helmert transformation has been told that there is no scale difference between the two systems. If there really is a scale difference, the output coordinates of the control points will not match their input values.
Thus, Scale Factor = 1 may have a different meaning in different contexts.
In this case, where the purpose of the transformation is to aid in locating monuments, it makes no difference.
But the lesson is, know what the input is and know what the desired output is to be.
