![]() While the Earth appears to be round when viewed from the vantage point of space, it is actually closer to an ellipsoid. When combined with other positioning data in the National Spatial Reference System, processed CORS data can provide latitude, longitude, and height positions accurate to within a few centimeters. NOS’s National Geodetic Survey manages a network of stationary global positioning satellite receivers called Continuously Operating Reference Stations (CORS). A constellation of over 30 global positioning satellites orbit the Earth, transmitting signals to receivers on land. We still look to the sky to determine our position, but the equipment is a bit more sophisticated. This process was more complex in the southern hemisphere, where the North Star is not visible. If the North Star was 60 degrees above the horizon, the observer was at 60 degrees latitude (north). The calculations were simple, so measuring latitude at sea was reliable hundreds of years before accurate longitude measurements could be calculated during a voyage. By calculating the angle between the horizon and a celestial object (usually the sun or the North Star), navigators could determine their approximate latitude using basic tools. Latitude and longitude have been used in astronomy and navigation since ancient times. No matter where you are on Earth, latitude lines are the same distance apart. Unlike longitude lines, which get closer to each other at the poles, latitude lines are parallel. A second of latitude covers only about 30.7 meters. One degree of latitude can be further divided into 60 minutes, and one minute can be further divided into 60 seconds. They mark the boundaries of the Arctic and Antarctic regions.Įach degree of latitude covers about 111 kilometers on the Earth’s surface. The Arctic Circle and the Antarctic Circle are at roughly 66 degrees north and south, respectively. The Tropic of Cancer, at roughly 23 degrees north, and the Tropic of Capricorn, at roughly 23 degrees south, are the boundaries of what we consider the tropics. They’re based on the sun’s position during Earth’s orbit, and they help us understand climate, weather, and ocean currents. Satellite data replaced human observations in the 1980s, but the data from the observatories is still being used. Another observatory was built in Ukiah, California, joining international stations at locations along the 39th parallel north. Coast and Geodetic Survey (later incorporated into NOS) built an observatory near his home in Gaithersburg, Maryland, and began collecting latitude measurements as part of a global project to monitor the wobble of the Earth on its polar axis. ![]() ![]() Did you know that the National Ocean Service (NOS) has been monitoring latitude since 1899? A scientist with the U.S.
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