latitude and longitude

PSC 121 Prince George’s Community College Barbara GagePSC 121 Prince George’s Community College Barbara Gage

Latitude and Latitude and LongitudeLongitude


Coordinate SystemsCoordinate Systems

When you are When you are locating a point on a locating a point on a flat surface you can flat surface you can use Cartesian use Cartesian coordinates of x and coordinates of x and y.y.

The point 2, 3 is The point 2, 3 is plotted on the plotted on the graph.graph.

x-axis

y-a

xis


Coordinate SystemsCoordinate Systems On a body such On a body such

as the Earth or as the Earth or our moon, we our moon, we can pinpoint can pinpoint the location of the location of any city or any city or landmark using landmark using two values, the two values, the latitude and latitude and longitude. longitude. These are polar These are polar coordinates.coordinates.


On the Earth there On the Earth there are two additional are two additional sets of reference sets of reference points.points.

The The EquatorEquator divides the Earth divides the Earth into the into the Northern Northern HemisphereHemisphere and and the the Southern Southern HemisphereHemisphere..

http://nationalatlas.gov/articles/mapping/IMAGES/latlong2.gif


The The Prime MeridianPrime Meridian divides the Earth divides the Earth into the into the Western Western HemisphereHemisphere and and the the Eastern Eastern HemisphereHemisphere..

http://www.arcticice.org/images/long.gif


LatitudeLatitude LatitudeLatitude is defined as is defined as

the elevation of the the elevation of the location point above location point above (or below) the (or below) the equator.equator.

The measurement is The measurement is expressed in expressed in degrees, minutes, degrees, minutes, and seconds.and seconds.

The equator is at 0° The equator is at 0° and the poles are at and the poles are at 90°.90°.

http://webhelp.esri.com/arcgisdesktop/9.2/published_images/LatLong%20from%20Globe%20Center.gif


LatitudeLatitude

If the location point If the location point is north of the is north of the equator an N or + equator an N or + is added to the is added to the degrees.degrees.

If the point is to the If the point is to the south of the south of the equator an S or – is equator an S or – is added to the value.added to the value.

52°N or +52°

24°S or -24°


LatitudeLatitude On the Earth we designate lines of equal On the Earth we designate lines of equal

latitude as latitude as parallelsparallels..

http://www.lakelandsd.com/tutorial/latitude2.jpg


LongitudeLongitude

LongitudeLongitude is is defined as the defined as the measurement of measurement of the location point the location point east or west of the east or west of the Prime MeridianPrime Meridian

The value is also The value is also expressed in expressed in degrees, minutes, degrees, minutes, and seconds.and seconds.

Note: There are 60 minutes in a degree and 60 seconds in a minute.


LongitudeLongitude

If the point is If the point is located to the west located to the west of the Prime of the Prime Meridian we add a Meridian we add a W to the value.W to the value.

If the point is If the point is located east of the located east of the Prime Meridian we Prime Meridian we add an E after the add an E after the valuevalue

30°W

80°E


LongitudeLongitude On the Earth we On the Earth we

designate lines of designate lines of equal longitude as equal longitude as meridiansmeridians..

The Prime Meridian The Prime Meridian has a value of 0° and has a value of 0° and no E or W. The no E or W. The longitude values longitude values increase up to 180° in increase up to 180° in both directions.both directions.

http://www.lakelandsd.com/tutorial/latitude2.jpg


Longitude and TimeLongitude and Time

Local noon poses a problem for Local noon poses a problem for travelers because it is noon at travelers because it is noon at different times in different locations. different times in different locations. That means that timetables are That means that timetables are useless.useless.

To solve this problem time has been To solve this problem time has been gauged from the Prime Meridian also gauged from the Prime Meridian also called the Greenwich Meridian (since called the Greenwich Meridian (since it passes through the Royal it passes through the Royal Observatory in Greenwich, England).Observatory in Greenwich, England).


Longitude and TimeLongitude and Time If you place meridians 15° apart starting with the If you place meridians 15° apart starting with the

Prime Meridian, you will divide the Earth into 24 Prime Meridian, you will divide the Earth into 24 zones. These correspond to the 24 hours in a day.zones. These correspond to the 24 hours in a day.

http://www.mapsofworld.com/time-zone-map/maps/world-time-zone.jpg


Longitude and TimeLongitude and Time As you travel around the world to the east, As you travel around the world to the east,

you gain an hour in time for each zone you you gain an hour in time for each zone you cross. If you travel to the west you lose an cross. If you travel to the west you lose an hour.hour.

http://www.astro.ufl.edu/~oliver/ast3722/lectures/CoordsNtime/timezon2.gif


But…But… If you traveled around the world to the If you traveled around the world to the

east fast enough you would be a day east fast enough you would be a day older in a short time!older in a short time!

If you traveled west you could go back If you traveled west you could go back in the past!in the past!

To solve this problem it was agreed To solve this problem it was agreed that the 180° meridian would signal that the 180° meridian would signal the change of date point.the change of date point.

Travel east and the date goes back Travel east and the date goes back one day; travel west and you advance one day; travel west and you advance a day when crossing this meridian.a day when crossing this meridian.


But…But… To keep all of a To keep all of a

country in the country in the same time zone, same time zone, the International the International Date Line does not Date Line does not follow the 180° follow the 180° meridian exactly.meridian exactly.

Other time zones Other time zones make the same make the same accommodations accommodations for country or state for country or state boundaries.boundaries.

latitude and longitude

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