#
**Theory**

##
*How does X-Plane's local coordinate system relate
to
real world coordinates?*

The entire X-Plane environment runs in a local coordinate
system
that contains a 3x2 degree chunk of the earth's surface, with you
somewhere
near the middle. As you travel, X-Plane adds whole degrees of scenery
in
front of your and drops them behind you.
X, Y, and Z in the local coordinate system are defined as
follows:

- X relates to Longitude - Positive is east (approximately)
- Y relates to Altitude - Positive is up (approximately)
- Z relates to Latitude - Positive is south (approximately)

I say approximately because X-Plane models a round world, so unless
you're
at the equator the latitude lines are curved, and the earth's surface
is
curved.
Units are in meters. The XYZ space mapped by X-Plane is an area
3 degrees
of longitude wide and 2 degrees of latitude high, approximately
centered
on the aircraft. The origin is the center of the space; zero Y is
approximately
sea level. The space is oriented such that X, Y, and Z exactly line up
with east, up, and south at the center of the 3x2 space.

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