Geographic coordinate system facts for kids
A geographical coordinate system is a coordinate system. This means that every place can be specified by a set of numbers, called coordinates.
Think of it as a special grid drawn over the Earth, helping us locate everything from your house to the highest mountain peak.
Contents
Latitude and Longitude
The system uses two main lines: latitude and longitude.
- Latitude: These lines run horizontally. They measure how far north or south a place is from the Equator. The Equator is the imaginary line that circles the Earth exactly halfway between the North and South Poles. Latitude is measured in degrees (°), minutes ('), and seconds ("). The Equator is 0° latitude. The North Pole is 90° North, and the South Pole is 90° South. So, the further you go from the Equator, the higher your latitude number gets.
- Longitude: These lines run vertically. They measure how far east or west a place is from the Prime Meridian. The Prime Meridian is an imaginary line that runs from the North Pole to the South Pole, passing through Greenwich, England. Longitude is also measured in degrees (°), minutes ('), and seconds ("). The Prime Meridian is 0° longitude. Lines of longitude go up to 180° East and 180° West. These two lines meet at the International Date Line, which is mostly, but not exactly, the same as 180° longitude.
Understanding degrees, minutes, and seconds
Each degree of latitude and longitude is further divided into 60 minutes, and each minute is further divided into 60 seconds. This gives us a very precise way to locate places. For example, the coordinates 34°15'12" N, 118°14'30" W pinpoint a location in Los Angeles, California. The "N" and "W" tell us it's North of the Equator and West of the Prime Meridian.
Why is this important?
Geographic coordinate systems are super important for many reasons:
- Navigation: Ships, airplanes, and even self-driving cars use these coordinates to navigate across the globe. Imagine trying to sail across the ocean without knowing your exact location!
- Mapping: Cartographers (mapmakers) use these coordinates to create accurate maps. They help us understand where countries, cities, mountains, and rivers are located.
- Science: Scientists use geographic coordinates to track weather patterns, monitor animal migrations, and study changes in the Earth's environment. They can pinpoint exactly where a volcano erupted or where a specific type of plant grows.
- Emergency Services: Emergency responders use coordinates to quickly locate people in need of help. If someone is lost in the wilderness, their location can be pinpointed using GPS (Global Positioning System), which relies on these coordinates.
- Land surveying: Surveyors use these coordinates to accurately measure and map land boundaries. This is crucial for building houses, roads, and other structures.
History
The invention of a geographic coordinate system is generally credited to Eratosthenes of Cyrene, who composed his now-lost Geography at the Library of Alexandria in the 3rd century BC. A century later, Hipparchus of Nicaea improved on this system by determining latitude from stellar measurements rather than solar altitude and determining longitude by timings of lunar eclipses, rather than dead reckoning. In the 1st or 2nd century, Marinus of Tyre compiled an extensive gazetteer and mathematically-plotted world map using coordinates measured east from a prime meridian at the westernmost known land, designated the Fortunate Isles, off the coast of western Africa around the Canary or Cape Verde Islands, and measured north or south of the island of Rhodes off Asia Minor. Ptolemy credited him with the full adoption of longitude and latitude, rather than measuring latitude in terms of the length of the midsummer day.
Ptolemy's 2nd-century Geography used the same prime meridian but measured latitude from the Equator instead. After their work was translated into Arabic in the 9th century, Al-Khwārizmī's Book of the Description of the Earth corrected Marinus' and Ptolemy's errors regarding the length of the Mediterranean Sea, causing medieval Arabic cartography to use a prime meridian around 10° east of Ptolemy's line. Mathematical cartography resumed in Europe following Maximus Planudes' recovery of Ptolemy's text a little before 1300; the text was translated into Latin at Florence by Jacobus Angelus around 1407.
In 1884, the United States hosted the International Meridian Conference, attended by representatives from twenty-five nations. Twenty-two of them agreed to adopt the longitude of the Royal Observatory in Greenwich, England as the zero-reference line. The Dominican Republic voted against the motion, while France and Brazil abstained. France adopted Greenwich Mean Time in place of local determinations by the Paris Observatory in 1911.
Different Coordinate Systems
While latitude and longitude are the most common, there are other coordinate systems used for specific purposes. These systems might use different reference points or projections to represent the Earth's curved surface on a flat map. Some examples include:
- UTM (Universal Transverse Mercator): This system divides the Earth into 60 zones, each with its own coordinate system. It's often used for mapping and surveying large areas.
- State Plane Coordinate Systems: These systems are specific to individual states or regions and are designed to minimize distortion in maps.
- Geographic Information Systems (GIS): GIS uses coordinate systems to store and manage geographic data, allowing us to analyze and visualize information about the Earth.
Fun facts
- The International Date Line isn't a straight line! It zigzags to avoid splitting countries in half.
- The Earth is not perfectly spherical; it's slightly flattened at the poles and bulging at the equator. This affects the accuracy of coordinate systems.
- GPS satellites orbit the Earth and constantly send signals that allow GPS receivers to determine their precise location using latitude and longitude.
- Many online map services, like Google Maps, use geographic coordinate systems to display locations and provide directions.
- The development of accurate clocks was crucial to the development of accurate longitude measurements. Before accurate clocks, determining longitude at sea was a major challenge.
See also
In Spanish: Coordenadas geográficas para niños
