Maps provide pictures of areas and regions that can tell us many things through correct interpretation. The Earth is approximately a sphere, and locations on its surface are commonly described using latitude and longitude, which are angular distances measured from the center. The Earth is most accurately described as an oblate spheroid, flattened at the poles and bulging at the equator. Observation of changes in the altitude of Polaris as one moves north or south provides evidence that the Earth is spherical.
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Introduction to MapsIntroduction to Maps
Maps are an extremely useful tool forMaps are an extremely useful tool for
many science and non-sciencemany science and non-science
disciplines.disciplines.
They provide “pictures” ofThey provide “pictures” of
areas/regions/land surfaces!areas/regions/land surfaces!
Correct interpretation can tell you MANYCorrect interpretation can tell you MANY
things!things!
– MINGOMINGO!!
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Location on EarthLocation on Earth
The earth is a sphere, soThe earth is a sphere, so
how do we describe where ahow do we describe where a
point is on its surface?point is on its surface?
The most common way toThe most common way to
locate points on the surfacelocate points on the surface
is by basic, geographicis by basic, geographic
coordinates: latitude andcoordinates: latitude and
longitude.longitude.
These coordinates valuesThese coordinates values
are measured in degrees,are measured in degrees,
and represent angularand represent angular
distances calculated from thedistances calculated from the
center of the Earth.center of the Earth.
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Shape of the EarthShape of the Earth
Earth is mostEarth is most
accuratelyaccurately
described as andescribed as an
oblate spheroidoblate spheroid
(almost a sphere).(almost a sphere).
Flattened at theFlattened at the
polespoles
1.1. Bulges at theBulges at the
equatorequator
NPSP
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Determining Earth’s ShapeDetermining Earth’s Shape
1.1. Observation of the North Star, Polaris.Observation of the North Star, Polaris.
– Altitude is theAltitude is the heightheight, measured in, measured in degreesdegrees
above the horizon of the observer.above the horizon of the observer.
– The altitude of Polaris changes as anThe altitude of Polaris changes as an
observer moves north or south (in theobserver moves north or south (in the
Northern hemisphere); this is because EarthNorthern hemisphere); this is because Earth
isis sphericalspherical and its surface isand its surface is curvedcurved..
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LatitudeLatitude Altitude ofAltitude of
PolarisPolaris
00oo
00oo
9090oo
9090oo
6565oo
6565oo
d. Summary: The altitude of Polaris (above the
horizon) is equal to the latitude of the observer on
the globe.
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Locating the North Star -Locating the North Star - of course youof course you
would need to be in thewould need to be in the NorthernNorthern hemisphere!hemisphere!
•The North Star is located at the end of the handle of the Little Dipper.
•The North Star always points in the direction of True North. For this reason
it has been used as and aid to navigation for many centuries.
8. Finding LocationsFinding Locations
on the Earthon the Earth
There are three main reference points:There are three main reference points:
EquatorEquator
NorthNorth andand South Geographic PolesSouth Geographic Poles
9. Latitude (parallels)Latitude (parallels)
Describe positionsDescribe positions NorthNorth andand SouthSouth of theof the
equator. Parallels runequator. Parallels run easteast toto westwest around thearound the
world.world.
Parallels are measure inParallels are measure in degreesdegrees fromfrom 00 toto 9090..
Those that are above the equator are labeledThose that are above the equator are labeled
NorthNorth; those below are labeled; those below are labeled SouthSouth..
Each degree of latitude consists of 60 equalEach degree of latitude consists of 60 equal
parts calledparts called minutesminutes..
o Each minute is divided intoEach minute is divided into 60 seconds60 seconds
Example: 38Example: 38oo
53’ 51”53’ 51”
12. Longitude (meridians)Longitude (meridians)
Describes positionsDescribes positions EastEast andand WestWest of the Primeof the Prime
Meridian. Meridians runMeridian. Meridians run northnorth andand southsouth around thearound the
world.world.
The 0The 0oo
meridian is called themeridian is called the Prime MeridianPrime Meridian and runsand runs
directly throughdirectly through Greenwich, EnglandGreenwich, England..
LocationsLocations easteast of Prime Meridian have longitudesof Prime Meridian have longitudes
betweenbetween 0 and 1800 and 180oo
EE. Locations west of the Prime. Locations west of the Prime
Meridian have longitudes betweenMeridian have longitudes between 0 and 1800 and 180oo
WW..
Longitude can also be broken down intoLongitude can also be broken down into minutesminutes andand
secondsseconds..
14. Great Circles & Finding DirectionGreat Circles & Finding Direction
Great circles are used in navigation, generally byGreat circles are used in navigation, generally by
pilotspilots. A great circle is any circle that. A great circle is any circle that dividesdivides
the globe in halvesthe globe in halves..
Geomagnetic PolesGeomagnetic Poles – points on Earth directly– points on Earth directly
above imaginary magnetsabove imaginary magnets
Magnetic declinationMagnetic declination – angle between direction– angle between direction
of geographic poles and the compass needleof geographic poles and the compass needle
True NorthTrue North – the direction of the geographic North– the direction of the geographic North
PolePole
15. Mapping the Earth’s SurfaceMapping the Earth’s Surface
CartographyCartography – science of map making– science of map making
MapsMaps – flat representations of Earth– flat representations of Earth
The best representation of earth is aThe best representation of earth is a globeglobe..
No matter what type of map is made, someNo matter what type of map is made, some
portion is always distorted.portion is always distorted. CartographersCartographers
work to minimize the effects of thesework to minimize the effects of these
distortions.distortions.
16. Reading a MapReading a Map
LegendLegend - list of symbols and their meanings- list of symbols and their meanings
ScaleScale – indicates the relationship (a ratio)– indicates the relationship (a ratio)
between the distances on the map and thebetween the distances on the map and the
actual distanceactual distance
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D. Position Characteristics –D. Position Characteristics – How can theHow can the
characteristics of a position be measured and described?characteristics of a position be measured and described?
1)1) Isolines –Isolines – lineslines
on a f ield mapon a f ield map
t hatt hat connectconnect
point s ofpoint s of equalequal
value.value.
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Examples of isolines:Examples of isolines:
a)a) Contour LinesContour Lines (Topogr aphic) – lines t hat(Topogr aphic) – lines t hat
connect point s of equalconnect point s of equal ElevationElevation..
b)b) IsobarsIsobars – lines t hat connect point s of equal– lines t hat connect point s of equal
pressurepressure. Found on a. Found on a weather mapweather map..
c)c) IsothermsIsotherms – lines t hat connect point s of– lines t hat connect point s of
equalequal temperaturetemperature. Found on a. Found on a weatherweather
mapmap..
d)d) IsosurfaceIsosurface – A model that represents field– A model that represents field
characteristics in 3-D.characteristics in 3-D.
20. Features of Topographic MapsFeatures of Topographic Maps
ElevationElevation – height above sea level– height above sea level
Sea levelSea level – point between the highest and lowest tide– point between the highest and lowest tide
levels (elevation at sea level = 0)levels (elevation at sea level = 0)
Contour linesContour lines – used to show elevation and connect– used to show elevation and connect
all points on the map with equal elevationall points on the map with equal elevation
Contour intervalContour interval – difference in elevation between– difference in elevation between
one contour line and the nextone contour line and the next
ReliefRelief – difference in elevation between the highest– difference in elevation between the highest
and lowest pointsand lowest points
Index contourIndex contour – every 5– every 5thth
line is BOLD and itsline is BOLD and its
elevation is labeledelevation is labeled
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Contour Lines:
Connect all points on
a map that have the
same elevation above
sea level.
22. Topographic MapsTopographic Maps
Colors on topographic maps:Colors on topographic maps:
– Blue:Blue: Water (rivers, lakes, streams, etc.)Water (rivers, lakes, streams, etc.)
– Green:Green: VegetationVegetation
– Red:Red: Contour LinesContour Lines
23. Topographic MapsTopographic Maps
There are many symbols used on theThere are many symbols used on the
map. These are explained in themap. These are explained in the
legendlegend..
24. Topographic MapsTopographic Maps
Contour lines spaced close together indicate aContour lines spaced close together indicate a steepsteep
slope.slope.
Contour lines spaced far apart indicate aContour lines spaced far apart indicate a gentlegentle
slopeslope..
Contour lines that form a closed loop indicate aContour lines that form a closed loop indicate a hillhill..
Contour lines that form a circle with dashed linesContour lines that form a circle with dashed lines
indicate a depressionindicate a depression..
V-shaped contour lines indicate aV-shaped contour lines indicate a valleyvalley and the “V”and the “V”
will pointwill point downstreamdownstream. (Rivers flow DOWNHILL). (Rivers flow DOWNHILL)
26. Topographic MapsTopographic Maps
Advanced TechnologyAdvanced Technology: Gives us the: Gives us the
ability to measure and analyze theability to measure and analyze the
physical properties of Earth with muchphysical properties of Earth with much
greater precision.greater precision.
– Examples:Examples: GPSGPS andand Weather satellitesWeather satellites..
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Features of Topographic Maps
Relationship between 3D and 2D representation
3D view
2D view
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Contour lines
Relationship between topographic features and contour lines
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Topographic Profile
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The RESULT – a 3-D pictureThe RESULT – a 3-D picture
