Coordinates Input displays the latitude and longitude coordinates in degrees, minutes, seconds decimal, degrees minutes decimal and degrees decimal of the center point of the left map.
Antipodal Coordinates displays the latitude and longitude coordinates of the opposite point of the left map's center. This "opposite" point is displayed on the right map.
Locations displays the reverse geocoded location of the current latitude and longitude (approximation only) and its antipodal point on the other side of the earth. Click the arrow to geocode the locations.
Antipode Map Controls Select the "decouple" check box to allow the two maps to zoom independently of each other. Click the "geocode" arrow to geocode the current coordinates. Click the "swap maps" arrows to swap the left and right maps.
Load Location load a location by coordinates or location name. Enter the desired value and click the load arrow to the right of the appropriate field or hit the enter key. Latitude & longitude accept degrees decimal, degrees minutes decimal or degrees minutes and seconds decimal.
The antipode of a point on the surface of a sphere is the point on the other side of the sphere defined by a straight line running from the origin point, through the center of the sphere and intersecting the sphere on the other side. It is the furthest possible point on a sphere from the origin point on the same sphere.
Since most of Earth is covered in water and most of the Earth's land is in the northern hemisphere most points on land have antipodal points in water.
To dig the proverbial hole to China you'd have to start in South America. Opposite the continental US is the Indian Ocean. In fact, there are only two US states that have antipodal points on land. They are the last two to join the Union, Alaska (Antarctica) and Hawaii (Botswana, Africa). Well, okay, Montana has a tiny little bit, too.