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| ![](https://web.archive.org/web/20100324100727im_/http://math.rice.edu/~lanius/images/bluwld.gif) Mathematics of Cartography
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Great!
Interactive Map Site
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Mathematics Topics-Coordinate System
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Coordinate systems
Numeric methods of representing locations on the earth's surface.
Latitude and Longitude
The most commonly used coordinate system today is latitude and longitude- angle
measures, expressed in degrees, minutes, and seconds.
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Equator and Prime Meridian
The Equator and the Prime Meridian are the reference lines used to measure latitude and longitude. The equator which lies halfway between the poles is a natural reference for latitude. A line through Greenwich, England, just outside London, is the Prime Meridian.
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| ![](https://web.archive.org/web/20100324100727im_/http://math.rice.edu/~lanius/images/glb.gif)
Latitude- Parallels that run east-west.
Longitude- Meridians that run north-south.
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Latitude runs from 0? at the
equator to 90?N or 90?S at the poles.
These lines
of latitude, called parallels, run in an east-west direction.
Lines of longitude, called meridians, run in a
north-south direction intersecting at both poles.
Longitude runs
from 0? at the prime meridian to 180? east
or west, halfway around the globe.
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| More on Degrees, Minutes, and Seconds
On the globe, one degree of latitude
equals approximately 70 miles.
One minute is just over a mile, and one
second is around 100 feet. Length of a degree of
longitude varies, from 69 miles at the equator
to 0 at the poles. Because meridians converge
at the poles, degrees of longitude tend to 0.
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| Longitude and Time
Since the earth rotates 360 degrees every 24 hours, or 15 degrees every hour, it's divided into 24 time zones- 15 degrees of longitude each. When it is noon at Greenwich, it is 10:00 A.M. 30 degrees W., 6:00 A.M. 90 degrees W., and midnight at 180 degrees on the opposite side of the earth.
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Historical Note
The planet gave no clear direction on selecting the Prime Meridian, as it did with the equator lying half-way between the poles as the 0 degree of latitude. As late as 1881, there were 14 different prime meridians still being used on topographic survey maps alone.
The International Meridian Conference of 1884
adopted the
Prime Meridian line
passing through the Greenwich Observatory near London, England. Take a trip down the
Prime Meridian
and explore the countries that lie on it.
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Email any comments to lanius@math.rice.edu
Copyright December 1996-2004 Cynthia Lanius
URL http://math.rice.edu/~lanius/pres/map/mapcoo.html
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