Tunnel Map of Ho Chi Minh City, Vietnam

Latitude, Longitude input fields allow you to load a specific point to find its antipode. Enter a latitude into the first field and a longitude into the second. Clicking a map will center it on the clicked location and the other map on its antipode. The left (or top) map's location will be loaded into the latitude and longitude fields. Entering return in the longitude field, or clicking , will geocode the coordinates.

Location input the value of a location, for which you want to find coordinates, into this field. Enter return, or click , to geocode it.

Load This button only appears if the latitude-longitude or location fields aren't empty. Clicking it will geocode/reverse geocode the fields, respectively.

Clear This button only appears if the latitude-longitude or location fields aren't all empty. Clicking it will clear these fields.

Location Menu allows the user to load antipodal location pairs from many different localities. This menu is only visible when the latitude, longitude and location fields are empty.

Primary displays the name or address of the location in center point of the left (or top) map.

Antipode displays the name or address of the primary location's antipode, which is the center point of the right (or bottom) map.

Sync Zoom Select this check box to allow the two maps to zoom together.

Display Crosshairs Select this check box to display crosshairs centered on each map.

Highlight Zoomed Area Select this check box to highlight the zoomed area of the other map (doesn't highlight when zoom levels are equal).

Swap Maps Swaps the two maps.

Displays the latitude-longitude coordinates of the cursor while over the left map.

Displays the latitude-longitude coordinates of the cursor while over the right map.

Displays the latitude-longitude coordinates of the center point of the left map.

Displays the latitude-longitude coordinates of the center point of the right map.

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 four US states that have antipodal points on land. They are the last two to join the Union, Alaska (Antarctica) and Hawaii (Botswana, Africa). There's also Colorado, near Lamar (Ile Amsterdam) and near Kit Carson (Ile Saint-Paul) and Montana has a tiny little bit, too.