An attempt to understand computing and computers
Antikythera mechanism
Astrolebe vs GPS
GPS replaced astrolabe
Astrolabe
This helped to
check the location of the stars.
altitude of objects over the horizon
While devices from different regions and time periods could vary widely—depending on their intended purpose and who made them, they could be as small as a coffee saucer or as large as a trash can lid, and made out of anything from wood to brass—they shared a similar structure.
Because the geography of the sky changes with your latitude, astrolabes commonly came with a series of plates associated with different latitudes of large cities. And though they could have been made out of a variety of materials, the majority that remain intact today are made of brass, very ornate, and are often associated with the educated elite, says Gingerich.
The Parts of an Astrolabe (also read: https://www.skyatnightmagazine.com/top-astronomy-kit/astrolabe)
Mater
The mater (Latin for mother) is the main body of the astrolabe. The edge of the mater is called the limb, on which are the degree scale and scale of hours are engraved. The hollowed-out part of the mater is called the womb and contains the latitude plates.
Plate
To an observer on the Earth it appears that our planet is at the centre of an immense sphere with the stars and other heavenly bodies located on its inside surface. Called the celestial sphere, it appears to rotate around the Earth.
The celestial sphere is mapped on the plate of an astrolabe using a mathematical technique called stereographic projection. This technique allows the 3-dimensional sphere to be represented on the 2-dimensional flat plate. Each latitude needs its own projection, and so most astrolabes come with a variety of plates for particular latitudes. usually stacked one on top of the other, within the astrolabe.
stereographic projection
GPS
The origins of GPS technology date back to World War II, when the U.S. and British navies deployed navigation systems that used ground-based radio signals. But the idea really got off the ground when the Soviet Union launched Sputnik — the world's first artificial satellite — in 1957.
Just days after Sputnik's launch, American scientists noticed that they could pinpoint the satellite's location based on the Doppler shift of its radio signals — a measure of how the wavelengths seemed to stretch out or contract depending on the satellite's movements.
This got the researchers thinking about creating a space-based navigation system. In the late 1950s, they began developing and testing satellite navigation technology, and the U.S. Navy deployed the operational Transit satellite system in the 1960s.
GPS relies on very accurate atomic clocks carried on the satellites. Each satellite emits signals that enable receivers to determine their location and time, according to the FAA.
The receiver on Earth computes the time difference between the time of signal reception and the time it was sent by the satellite to compute the distance between the receiver and the satellite. The receiver needs signals from at least four satellites to be able to compute an accurate position.
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