THE GEOGRAPHIC GRID: LATITUDE AND LONGITUDE.

The geographic grid.

The Geographic grid is the system of coordinates that we use in order to locate any point in the Earth’s surface.

Both extremes of the Earth´s axis are connected to two fixed points: the poles

From these points we trace imaginary lines that cross with others to form a grid.

Parallels and meridians.

This system is based in two types of imaginary lines: parallels and meridians:

• Parallels: Imaginary lines that encircle the Earth, perpendicular to its axes.

The main line of latitude is the Equator which divides the Earth into two halves. Another important parallels are the Tropic of Cancer, located in the Northern Hemisphere and the Tropic of Capricorn, located in the Southern Hemisphere.

• Meridians: Imaginary semicircles traced from pole to pole.

The most important meridian is the meridian 0º or Greenwich meridian, which runs through Greenwich, near London.

Latitude and longitude.
We use this imaginary lines in order to establish the latitude and the longitude of a point located in the Earth’s surface.


Latitude: The distance, measured in degrees, from any given point to parallel oº or  the equator

The maximum  latitude is 90º and can be either north or south.

Longitude: The distance, measured in degrees, from any given point to meridian 0º or Greenwich

The maximum longitude is 180º and can be either  east or west.

Remember: every degree (º) can be divided into 60 minutes (') and every minute can be divided into 60 seconds (''), the same way than an a hour. For example, the geographic coordinantes of the IES Cervantes High School are: 40º 24' and 12" N and 3º 42' 8" W.

ACTIVITIES:

1. Indicate the latitude and the longitude of the letters that appear in the following map.

2. Write down the concepts that correspond to the definitions in the table.

UNIT 1. THE EATRH AND ITS REPRESENTATION

With an A	The envelope of gases surrounding the Earth.
With a C	A system of projection that translates the meridians and parallels onto a cone. It is the most appropriate way to represent the mod-latitudes, between the tropics and the polar circles.
With a C	A projection system that translate the parallels and meridians onto a cylinder. It is the best method to represent the low latitudes between the equator and the tropics.
With a D	The time each morning at which daylight first begins. Sunrise.
With an E	A line notionally drawn on the earth equidistant from the poles, dividing the earth into northern and southern hemispheres and constituting the parallel of latitude 0.
Contains an F	The different shapes that the surface of the Earth has adopted over millions of year, as a result of internal forces.
With a G	A coordinate system that allows us to find every location on the Earth by its latitude and longitude.
With a G	A scale that use a graduated ruler to indicate the equivalent to ground distance.
With a H	Half of the earth, usually as divided into northern and southern halves by the equator, or into western and eastern halves by an imaginary line passing through the poles.
Contains an I	The time of year when the Sun´s rays fall perpendicular to one of tropics. A 24-hour night takes place in one of the poles while the other has a 24-hours day.
Contains  a K	The darker stage of twilight, especially in the evening. To become or make dark or dusky.
With an L	The distance, measured in degrees, from any given point to parallel 0º or the equator.
With an L	A year, occurring once every four years, which has 366 days including 29 February as an intercalary day. It is due to the orbit movement.
With a M	A representation of the spherical surface of the Earth, or a part of it, on a flat surface.
With an M	Imaginary semicircles traced from pole to pole. We use them to measure the longitude.
With an N	A scale that use a fraction to indicate the equivalent to ground distance. The numerator designates the distance on the map, and the denominator tells us its equivalent on the ground.
With an O	The movement of the Earth around the sun.
With a P	A celestial body moving in an elliptical orbit around a star.
With a P	A projection system that translates the meridians and parallels onto a plane that touches the Earth on one of the poles. It is the most appropriate method to represent the polar areas.
With a P	Imaginary lines that encircle the Earth, perpendicular to its axis. We use them to measure the latitude.
With an R	The turning of the Earth around its imaginary axis.
With an S	The number or graphic that indicates the relation between a distance drawn on the map and the same distance on the ground.
With a T	Any of the 24 longitudinal divisions of the earth's surface in which a standard time is kept.
With a T	A type of map that represents in detail the physical and human aspects of the territory: relief, water, flora, communication routes, land use etc.
With a T	A type of map that represents a specific geographical aspect such as climate, relief, population, etc.
Contains a  U	A distance, measured in degrees, from any given point to meridian 0º or Greenwich.
Contains an X	The time of year when the Sun´s rays fall perpendicular to the equator. The Sun illuminates the North Pole and the South Pole for the same number of hours.
Contains a Y	A sun with planets, asteroids, comets, etc. in orbit around it.

You can find the solution here.