N 51 59.420 E004 20.115 - Square second Delft, Netherlands
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naj16
N 51° 59.420 E 004° 20.115
31U E 591683 N 5760804
In Delft you can see just how big a square second is.
Waymark Code: WMH7BK
Location: Zuid-Holland, Netherlands
Date Posted: 06/03/2013
Views: 36
"If you want to to let people know where you are then you give them your coordinates using a system that has been in use for centuries: longitude and latitude. The surface of the earth is covered with two systems of lines: from the north to the south pole (meridians) and perpendicular to these, parallel to the equator (parallels). The meridian that runs through the Royal Observatory in Greenwich is called the zero meridian; together with the equator it forms a pair of axes, with the equator as x-axis and the zero meridian as y-axis.
The point where our axes meet is the origin of our coordinate system. Instead of x- and y-coordinates we use the terms longitude and latitude respectively and rather than positive and negative we say longitude east and longtude west, and latitude north and south. The unit that is chosen to express longitute and latitude is the degree; that makes sense because all lines are (parts of) circles. It is also useful to use degrees because the parallels get shorter the further away you get from the equator; at the poles they consist of just one point.
So, both axes are divided into degrees. The equator in two parts of 180 degrees each: west and east; the semicircle that completes the zero meridian into a circle around the earth is the meridian at 180° west and east. The zero meridian is divided in twice 90°: north and south.
The length of the zero meridian from equator to north pole is, by definition, 10.000 km (that was the original definition of the kilometre). This makes one degree correspond to roughly 111 km. This is quite a lot, so degrees are divided into 60 minutes and minutes are divided into 60 seconds. This is a remnant of the way the Babylonians used to write their numbers: in base 60. This makes one minute about 1850 meters, or a nautical mile; a second then corresponds to a little bit more than 30 meters.
Geografische Plaatsbepaling Delft
As the parallels get shorter, so do the degrees, minutes and seconds when measured along them. In Delft (the Netherlands), in the park Buitenhof, one can find a work of art from 1972 called Geografische Plaatsbepaling Delft (Geographic Location Delft) that shows how short a second has become at the corresponding latitude. It forms a rectangle that is bounded by two parallels and two meridians." Maths in the City
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