Chapter 3

Models of the Earth

Section 1: Finding Locations on EarthThe Earth is divided into hemispheres, North & South and East & West. These hemispheres are

then further divided into other areas.

Latitude Distance in degrees North or South of the equator Uses parallels as lines East and West of the equator

A parallel is any line that completely circles the Earth and is parallel to the equator. They are the same distance throughout the Earth’s SurfaceLat. of the equator is Oo

North Pole is 90o N.South Pole is 90o S. 1o of Lat is 1/360 of circumference 40,000

3601o of Lat is approx 111km1o = 60 minutes (60’) = 111km 1 minute of lat = 1.85km1 second of lat = 0.031

LongitudeDistance in degrees East or West of the Prime Meridian

Measured in meridiansA meridian is a circle that runs north and south

Furthest you can go is 180o away (circle is 360o)Divided into degrees and minutes (1o = 60’)

Closer the lines get together the further from the equator you are

At the equator 1o is about as long as 1o of latitude (111km), but the distance gets smaller the closer you are to the poles. The equator is a meridian.

Riverhead Long Island, New York is approx: 40o 55’ 1”N 72o 39’ 43”W Greenport Long Island, New York is approx: 41o 6” 12”N 72o 21’3”WDisney World, Florida is approx: 28o 24’ 41” N 81o 31’ 58” W

Great Circles Great circles are straight lines that go all the way around the center of the earth. The equator is the only line of latitude that is a great circle. Meridians of longitude that cross over the north and south poles are also great circles. For every location on a great circle, it's antipodal location is also on the circle. Other than the equator itself, any great circle crosses the equator at two antipodal locations, 180° apart. Other than the equator and meridians of longitude that run due north and south, any great circle reaches its maximum latitudes at two locations that are 90° of longitude east and west of the two locations where the great circle crosses the equator.

Antipode – the location 180° on the other side of the world. Example 40 north’s antipode would be 40 south, and so on.

Prime Meridian - the longitudinal line that passes through Greenwich, England Oo Long (also passes through Spain, Algeria, Ghana, Burkina and Mali) It dates back to October 1884. At the behest of the President of the United States of America 41 delegates from 25 nations met in Washington, DC, USA for the International Meridian Conference

Finding DirectionMagnetic declination

Is the difference of the angle between true north and magnetic north. This number will change as you move around the earth. This is because a compass will point toward the magnetic north (also called the geomagnetic north) and we use polar north for direction without a compass

Global Positioning System GPSTells position (latitude and longitude), speed and time (based on the global network) If used by the military can be accurate to the centimeterFound in most cars and can also be hand held with an accuracy of 10 to 15 meters.Very accurate because it 3 satellites for triangulation for accuracy

Earth Observing SystemEOSEstablished in 1999Unlike maps that show images, this system maps the changes in air from the ground to the atmosphere in all areas, even the water, it shows the exchange of carbon, water and energy.http://www-airs.jpl.nasa.gov/Technology/HistoricalContext/

Section 2 Mapping Earth's Surface Cartography- the science of making maps

Cartographer – Mapmakers

Uses data collected from various sources.Map - a way of looking at the earth; shows earth as flat - it is not therefore there is distortion

One Type of such a map is:Remote Sensing – using satellites or airplanes to gather information without being there

Map projection

A map is flat so it is hard to show depth, they accomplish this by using a technique called map projection.

Map Projection: A way of showing the curved earth as flat; there is still some distortion, either in distance or direction or both.

The three most popular map projections used today:

Cylindrical or Mercator projection It shows the whole world except extreme Polar Regions; shows true direction; polar region is exaggerated! Uses straight lines; looks like a grid. Used for sea navigation.

Azimuthal or Gnomonic projection It shows that a straight line between two points is the shortest

distance; direction and distance are not perfect. Looks like wedges - from the poles down. Used for air travel. Distorts both direction and distance.

Conic or polyconic projection Are a cone of a small area covered by these maps make them nearly correct in all aspects. Used by the U.S.G.S. (United States Geologic Survey). Lines of lat. and long have slight curves. When more than one conic map is used it is called Polyconic.

Reading Maps

Direction on a Map

You first need to figure out what compass direction you are looking at.

Most maps drawn by the United States Geological Survey (USGS) has North on top of the page. However, if north is not up on top they need a way of showing you direction by using a compass rose.

Compass Rose - usually a picture showing where North, East, South, West are located. Some maps may use only a single arrow to do this. Some use an elaborate pointed symbol.

SymbolsA legend is a list of symbols and their meanings. They include urban, city or other areas.

Symbols are standardized colors: ScalesMaps most also include a way to measure distances. They accomplish by using a scale.

Graphic - is printed and looks like a ruler

Fractional using ratios 1/100 - map size is one-hundredth real size 1: 100

Verbal - statement 1 Centimeter represents 50 kilometers

IsogramsIs a line of equal value. All points on the line are the same value. This can be

used for many different types of maps used in different sciences.

Section 3 Topographic Maps

Advantages of Topographic Maps•Uses natural features and constructed features to represent an area. They are made by using both aerial photos and survey points. •They show elevation.•They are very detailed maps about the surface of an area, it will cover all areas, size, shape, elevation.•Uses isolines to show outlines of land forms.

Benchmark - exact elevation on a brass or Al Plate- Done by U.S.G.S. to the nearest foot- Labeled BM on maps

Elevation of Topographic MapsRelief - the ability of a map to show land forms

1. Elevation - mountains, hills – High Points2. Depressions - kettle holes, valleys – Low Points

Contour lines:• Give exact elevation (depression) above sea level (below) and

show general shape of the land•Everywhere on the contour line is the same exact elevation•Can show areas of valleys, ridges, mountains, etc.Contour interval

Is the difference in elevation between two consecutive contour lines.Depression contours 1. Gives depression measurements2. Drawn with lines on inside of contour intervals

Landforms on Topographic MapsAny point on a contour line is exactly the elevation of the contour lineAny point between contour lines is an estimate in between the two contour linesNo contour lines - (few) very little change in elevationA lot of contour lines - very steep change in elevationClosed circles show tops of hillsA ridge is an oval contour lineRivers - Contour lines always point upstream from where the river is flowing

Topographic Map Symbols Contour lines are brown

Roads, buildings, railroads & works built by man are black Water is blue Woodland areas is green Highways are red Developed areas are pink

Profile- It is to make a side view of the area on a topographic map. It is also a cross sectional view of the area. This is important to be able to see what the features of the area are.

Gradient = Change in elevation (Ft)(Slope) distance (miles)

Other types of MapsGeologic - Shows the soils in and distribution of geologic features

Soil Maps - show information about area. Used by Natural Recourse Conservation Services (NRCS)