# Which two widths are actually points

### Info sheet The graticule of the earth Graticule

Circles of latitude, longitude, determination of geographical location and orientation on earth

#### introduction

The graticule of the earth is an imaginary line network drawn across the globe. It consists of vertically intersecting circles of latitude and longitude and is used to determine the geographical location and orientation on earth.

#### Parallels (parallel circles)

The equator (translated "equalizer") divides the earth into the northern and southern hemispheres. 90 parallels of latitude run parallel to the equator in the direction of the poles. The distance between two circles of latitude is always 111 km. The distances between the equatorial plane and the circles of latitude are measured as angles in the center of the earth and given as degrees of latitude. Thus counting from the equator to the north pole from 0 ° to 90 ° N (northern latitude) and from the equator to the south pole from 0 ° to 90 ° S (southern latitude).
With a circumference of around 40,000 km, the equator is the longest parallel. It is also called the "great circle". Towards the poles, the circumference of the parallels decreases. The north and south poles (90 ° N and 90 ° S) are only points.

#### Circles of length

The longitudes are perpendicular to the circles of latitude and all intersect in the north and south poles. There are a total of 180 longitudinal circles. They are counted from the prime meridian (0 °). A meridian is half a longitude that runs from pole to pole. The prime meridian has passed through the old observatory in Greenwich, a small suburb of London, England, since an international determination in 1911. From the prime meridian one counts 180 ° to the east (0 ° to 180 ° east longitude) and to the west (0 ° to 180 ° west longitude). On the opposite globe, in the middle of the Pacific Ocean, at 180 ° E / W is the date line.
All meridians are around 20,000 km long. The name means "noon line" and is based on the fact that all places on the same meridian have noon at the same time.
Since the longitudinal circles converge (converge) at the pole, the distance between two longitudinal circles decreases with increasing width. At the equator, the distance is greatest at 111 km. Towards the pole it goes towards zero.

#### use

The graticule of the earth serves as a basis for cartographic images, as an orientation aid and for determining the geographical position of every place on earth. The names of the geographical coordinates come from ancient seafaring. At that time they referred to the north-south and east-west extension of the Mediterranean.
Today the geographic coordinates (latitude and longitude) are used in long-distance navigation on ships and in airplanes. Before that, navigation on ships took place e.g. B. by observing the coast (terrestrial navigation) or by observing the stars (astronomical navigation).

#### Location

When specifying the position of a place, i.e. specifying the geographical coordinates, you first name the latitude and then the longitude. So is z. B. Kiel at 54 ° N (north latitude) and 10 ° E (east longitude).
For a more precise specification of the coordinates, the specification in degrees, minutes and seconds is used. This so-called sexagesimal notation comes from seafaring, where one minute of latitude corresponds to a nautical mile (1852m), or one latitude second corresponds to the 60th part of it (about 31m). The minutes of longitude decrease with the cosine of the geographical latitude from the equator to the poles. 60 minutes correspond to 1 ° and 1 minute again to 60 seconds.
Example: 9 ° 30'30 '' N / 12 ° 45'15 '' W (spoken 9 degrees, 30 minutes, 30 seconds north latitude and 12 degrees, 45 minutes, 15 seconds west longitude) corresponds to the converted 9.51 ° N / 12.754 ° W.
The conversion is done as follows:
First the seconds are converted into minutes (x '' 1 '/ 60' '), then the minutes are converted into degrees (x' 1 ° / 60 '). Together with the number of degrees, the result is the decimal notation. For the above example, the equations 9 + (30 + 30/60) / 60 = 9.51 or 12 + (45 + 15/60) / 60 = 12.754 apply (both results are rounded).

Keywords:
Earth, graticule

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