# 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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