Google says Earth's radius is 6371km.
One NASA web site sasy it is 6371.00 km. https://mobile.arc.nasa.gov/public/iexplore/missions/pages/solarsystem/earthfacts.html
WGS84 has it are 6378.1370 at equator and 6356.7523 to the north pole.
Wikipedia:
https://en.wikipedia.org/wiki/World_Geodetic_System#1984_version
It has a photo that depicts WGS84 with the non-round Earth, as well as a theoretical route Earth. They get the 6371 by a weighted average of both
with equatorial diameter representing 66% of it and the polar one 33%.
Anyone have an explanation on why equatorial is given twice the weight
as polar? Is that due to shape of Earth, or because it is felt
calculations are more likely for latitudes below roughly 45 (aka USA) ?
And from a NASA or any space business purposes, it it correct to state
that the ellipsoid nature of planet causes precession, and that since precession makes for real changes in orbit each day, that they need to
factor this in? Or would they use a round Earth model and apply a
precession "constant" ?
I think Marjory Taylor Green should be elected President of USA, she'd
have no problem declaring the Earth to be flat. Think about how much
simpler all distance calculations would be :-) (ok, Orbit become quite complex around an object shaped like a coin since circular orbits would
in act be highly elliptical, but NASA has scientists who can do the math
, right?
(All this because I am trying to match what Garmin's software calculates
as distance from some 2000 track points and I get to about 318.5km
instead of 319 :-)
Google says Earth's radius is 6371km.
One NASA web site sasy it is 6371.00 km. https://mobile.arc.nasa.gov/public/iexplore/missions/pages/solarsystem/earthfacts.html
WGS84 has it are 6378.1370 at equator and 6356.7523 to the north pole.
Wikipedia:
https://en.wikipedia.org/wiki/World_Geodetic_System#1984_version
It has a photo that depicts WGS84 with the non-round Earth, as well as a theoretical route Earth. They get the 6371 by a weighted average of both
with equatorial diameter representing 66% of it and the polar one 33%.
Anyone have an explanation on why equatorial is given twice the weight
as polar? Is that due to shape of Earth, or because it is felt
calculations are more likely for latitudes below roughly 45 (aka USA) ?
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