Advances in Mapping
Recent developments in mapping have redefined cartography, personal computers and GPS equipment, remote-sensing satellites, and the Internet have changed the ways map data are collected, manipulated, shared, and used.
The cartographic applications of remote sensing are nearly limitless, what with mapping and charting from space using satellites, space telescopes, and spacecraft in combination with many-layered softwere such as geographic information systems (GIS) and numerous databases. The surface of Earth is now pictured daily by numberous remote-sensing satellites, producing vast archives of mappable data that are received, analyzed, and maintained by cartographers, scintists, and technicians around the world.
Today most natural processes and the effects of many human activities can be rendered into map from as well, revealing Earth's secrets and giving a good picture of where the planet has been and where it is headed.
- What is Landsat?
Landsat is a series of unmanned scientific satellites equipped with cameras, ning in 1972. With a primary mission natural resources and monitoring atmospheric and oceanic conditions, landsat collects surface images in bands of 115 miles square and has the capability to rephotograph each area every 18 days. Overall, the landsat system provides low- and mediumresolution mapping.
Newer Landsat satellites have more data-gathering equipment, including a thematic mapper with resolution in seven spectral bands, or wavelengths of light.
In 1985 Landsat become private but was transferred back to govermment control in 1992. Landsat 8 was launched in february 2013, and has higher resolution instruments than earlier models.
- How does GPS work?
GPS-global positioning system-is a space-age version of triangulation, Originally developed for military use, GPS has three components; stations around the world, and receivers installed in locations ranging from naval destroyers to private golf carts.
In the U.S. GPS system, two dozen Navstar satellites orbit the planet every 12 hours, following six different orbits. There additional satellites orbit as backup. The satellites contain atomic clocks that send precise times with each signal. The control stations monitor the satellites, using remotecontrolled on-board thrusters to manage their positions.
When a GPS user on land or sea calls for location information, signals pass from orbiting satellites to that user's receiver.The length of time taken by the transmissions-usually a fraction of a second-helps determine distance to a point on an imaginary sphere, and the user's latitude and longitude can be calculated by using the mathematics of triangulation. Three satellites would suffice, but more provide redundancy and compensate for inaccuracies.
GPS Signals are broadcast on two different frequencies, one for military use and one for civilian use. Civilian augmentation can provide precise location to within 0.4 of an inch.
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