bocops
commented
3 years ago Nothing in that statement claims that it refers to WGS84 - and if it did, I would question the correctness of using the exact semi-major axis value but not the semi-minor axis value for a calculation that tries to roughly approximate lengths not only along the equator but also perpendicular to it.
Considering that
- these values don't differ in the first four digits, and would have the same fifth digit after rounding,
- the approximated lengths given in the table are rounded to four or less significant digits in all cases but one anyway,
- there's a much bigger error than any of that as soon as you step away from the equator a bit,
- there actually is an NB stating that this is just an approximation based on some assumption,
I'd say that, by all means, let's split the difference and call it 111320m, or 111257m if we use the average between semi-major and semi-minor, or 111194m if we base our calculation on what Wikipedia claims is the "mean radius" of Earth... or let's stop pretending that any of these values is really "better" than the others and that not using it is a sign of abundant sloppiness.
in the voice of an expert who cares more about all the things you are implementing than you do
Just BTW, this is borderline insulting and IMO uncalled for.
fulldecent
The document/specification/notes refer to the Earth as having a circumference of 111321 meters per degree of latitude.
However, elsewhere it is specified that plus codes are predicated over the WSG 84 standard.
The WSG 84 geoid sets the semi major axis at 6 378 137.0 m. (Sorry, can't find actual reference for this // https://en.wikipedia.org/wiki/World_Geodetic_System)
That means one degree is 6378137.0 2 π / 360 ≈ 111319.49.
Of no consequence. But still, all standards should be written consistently and in the voice of an expert who cares more about all the things you are implementing than you do.