Eartha
From Wikipedia, the free encyclopedia
Eartha, the world's largest rotating and revolving globe, is located within the headquarters of the DeLorme mapping corporation in Yarmouth, Maine. The globe weighs approximately 5,600 pounds (2,500 kg), and has a diameter of over 41 feet (12.5 m). This gives it a scale of 1:1,000,000, on which one inch represents 16 miles, one millimetre represents one kilometre. As with most globes, it is mounted at a 23.5 degree angle, the same axial tilt as the Earth itself; thus the equator is diagonal to the floor. It uses a cantilever mount with two motors, and simulates one day's revolution and rotation every minute.
The globe was completed on July 23, 1998, and it uses a composite database built from satellite imagery, shaded relief, colored bathymetry, and information about road networks and urban areas. The database used to generate the surface images was approximately 140 gigabytes.
Eartha is contained in an atrium with several glass walls that allow it to be seen from outside of the building; it is readily visible from U.S. Route 1. At night, the globe is illuminated.
The atrium containing Eartha is open to the public during business hours. There is an adjacent gift shop that carries various DeLorme and geography related products. The mounting equipment is in a large pit below floor level and is visible to visitors, but the stairway down is chained off to prevent public access. There are two balconies which allow visitors to more easily view the higher parts of the globe. Some offices within the building also have views overlooking Eartha.
Eartha is constructed around a truss structure which is called Omni-Span, and which consists of over 6000 pieces of aluminum tubing. This is covered by a skin of 792 map panels, each covering 8 degrees of latitude and 10 degrees of longitude, and attached to the trusses with a custom-designed system of hidden bolts.
Eartha was originally designed to be 42 feet in diameter. In 1999, surveyors hired by the Guinness Book of World Records measured the globe at 41 feet and 1.5 inches; while this is noted on the DeLorme web site (as of 2007-09-05), they also list the globe as 41.5 feet in diameter. David DeLorme, CEO of the DeLorme mapping company, is credited with the design. The previous record holder is the Globe of Peace located in Apecchio, Pesaro, Italy.
