Latitude and Longitude

1 / 23

# Latitude and Longitude - PowerPoint PPT Presentation

Latitude and Longitude. Finding Your Location on a Sphere. Coordinate Systems. When you are locating a point on a flat surface you can use Cartesian coordinates of x and y. The point 2, 3 is plotted on the graph. y-axis. x-axis. Coordinate Systems.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Latitude and Longitude' - conor

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Latitude and Longitude

Finding Your Location on a Sphere

PSC 121 Prince George’s Community College Barbara Gage

Coordinate Systems
• When you are locating a point on a flat surface you can use Cartesian coordinates of x and y.
• The point 2, 3 is plotted on the graph.

y-axis

x-axis

Coordinate Systems
• When you are locating a point in a 3-dimensional system you can use Cartesian coordinates of x, y, and z.
• The image shows the point 3, 2, 2 plotted.
Coordinate Systems
• When you are working with a curved surface such as a sphere, you need to use a different system, one based on angles (polar coordinates) measured from reference points.
• One of our reference points is the center of the Earth.

http://brownsharpie.courtneygibbons.org/wp-content/comics/2006/10/polarcoordinate.jpg

Coordinate Systems
• On a body such as the Earth or our moon, we can pinpoint the location of any city or landmark using two values, the latitude and longitude. These are polar coordinates.
• The Equator divides the Earth into the Northern Hemisphere and the Southern Hemisphere.

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

The Prime Meridian divides the Earth into the Western Hemisphere and the Eastern Hemisphere.

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

Latitude
• Latitude is defined as the elevation of the location point above (or below) the equator.
• The measurement is expressed in degrees, minutes, and seconds.
• The equator is at 0° and the poles are at 90°.

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

Latitude
• If the location point is north of the equator an N or + is added to the degrees.
• If the point is to the south of the equator an S or – is added to the value.

52°N or +52°

24°S or -24°

Latitude
• On the Earth we designate lines of equal latitude as parallels.

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

Longitude
• Longitude is defined as the measurement of the location point east or west of the Prime Meridian
• The value is also expressed in degrees, minutes, and seconds.

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

Longitude
• If the point is located to the west of the Prime Meridian we add a W to the value.
• If the point is located east of the Prime Meridian we add an E after the value

30°W

80°E

Longitude
• On the Earth we designate lines of equal longitude as meridians.
• The Prime Meridian has a value of 0° and no E or W. The longitude values increase up to 180° in both directions.

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

• As we explore and chart new planets, the way longitude is recorded has changed. Instead of 0-180° E and W, longitude measures start at the prime meridian and continue eastward all the way around the planet. New longitudes values run from 0-360°.
Longitude and Time
• When the Sun crosses the meridian that pinpoints your location we say that the time is “local noon”. Shadows are shortest at this time.

Longitude and Time
• Local noon poses a problem for travelers because it is noon at different times in different locations. That means that timetables are useless.
• To solve this problem time has been gauged from the Prime Meridian also called the Greenwich Meridian (since it passes through the Royal Observatory in Greenwich, England).
Longitude and Time
• If you place meridians 15° apart starting with the Prime Meridian, you will divide the Earth into 24 zones. These correspond to the 24 hours in a day.

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

Longitude and Time
• As you travel around the world to the east, you gain an hour in time for each zone you cross. If you travel to the west you lose an hour.

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

But…
• If you traveled around the world to the east fast enough you would be a day older in a short time!
• If you traveled west you could go back in the past!
• To solve this problem it was agreed that the 180° meridian would signal the change of date point.
• Travel east and the date goes back one day; travel west and you advance a day when crossing this meridian.
But…
• To keep all of a country in the same time zone, the International Date Line does not follow the 180° meridian exactly.
• Other time zones make the same accommodations for country or state boundaries.