Cartography Mapping the World. Cartography The art (science) of map making.
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Transcript of Cartography Mapping the World. Cartography The art (science) of map making.
Cartography
Mapping the World
Cartography
The art (science) of map making
Cartographer
One who makes or studies maps
Main Goal of Maps
To communicate information
MapDefined as: a graphic representation of the real world
symbolizes the features or conditions of these locations
Always abstraction of reality3D to 2 D???
Latitude & Longitude
The Map Coordinate System
Direction on a Map: Map Coordinate System
Latitude/longitudepinpointing a unique location on the Earth’s surface
All maps show same latitude and longitude for a particular point on the Earth’s surface
LatitudeDistance in degrees north and south of the equatorMeasured by parallels
Imaginary lines that circle the world from east to west parallel of the equator
Equator = 0°latitude
North Pole and South Pole = Points of latitude90°N and 90°S (1/4 of 360°)
90°N
LongitudeDistance in degrees east and west of the prime meridianMeasured by meridiansMeridians get closer together the further away from the equatorUsed for defining 24 time zones
Prime Meridian
Starting line for longitudinal systemPasses through Greenwich, England0° longitude180° is furthest meridian (360/2)
International Date Line
Coordinate SystemDegrees divided into minutes and seconds
5°20‘45“ 5 degrees, 20 minutes, 45 seconds
Latitude1° = 111 km
LongitudeNo set number of km1° = 4 minutes of time15 ° = 1 hour
Read latitude number FIRST, then longitude!!!
Finding Latitude in the NORTHERN HEMISPHERE
Angle of Polaris (North Star) = angle of latitude
Practice with PolarisWhat is the angle of Polaris at the following points?
ABCDE
What happens to the altitude of Polaris as you move from
A to DB to C
Finding Polaris
Practice with PolarisIf Polaris is 40° above the horizon, what is your
LatitudeLongitude
If you can’t see Polaris above the horizon, where are you?
Great Circles
Great circlesPlane passes through the center of the sphere
Small circlePlane does not pass through center of sphere
EquatorGreat circle
Each meridianHalf a great circle
Great Circle RouteShortest distance between two points on a sphereUsed for airplane travel
Time Zones
Earth’s 24 Time Zones
Why 24?24 hours to rotate on its axis
15° (longitude) each
Time zones adjustedLocal areas same Large areas divided
US has 6 time zones
International Date Line180° meridian (longitude)Traveling west, advance a dayTraveling east, lose a day
Sun
Mon
Parts of a Map
Scales, Legends & Symbols
Map Scalescompares distance on a map with actual distance of section of the Earth’s surface the smaller the map representation (piece of land), the larger the scale
Large Scale
-less area
-more detail
Small Scale
-more area
-less detail
Large vs Small Scale
Bigger the number = small ratio = smaller the scale because more area is covered
A C
B
Types of ScalesVerbal –
Word statement “1 centimeter = 50 kilometers”
Graphic – line is divided into equal parts and marked off into units of equal length
Numerical (fractional)– a fraction/ratio is used to show what part of true distance the map distance really represents 1/ 100 = any distance is one hundredth of the true distance1 : 100 = 1 unit of length on the map = 100 times the same unit on the map
LegendExplain what the symbols on a map represents
Topographic MapShow changes in elevation of the Earth’s surface, as well as, other features
Mountains, rivers, forests, bridges
Contours LinesConnect points of equal elevation
Fields & IsolinesField
Region in which a similar quantity can be measured at every point or location
IsolineLines that connect points of equal field value
Contour IntervalDifference between contour lines
4400-4000 = 400 ft
Index contour = elevation written
Reading Topographic Maps
The RulesMap scaleContour intervalDirection of stream flowSteepest sectionBenchmarkDepressionIslandsHighest elevation
X = Benchmark – scientifically determined elevation
“V” contour lines point to origin of river (point “up” stream)
Water flows down hill
V points up hill
Closed depressionGentle slopeSteep slope
Topographic Profile
Shows the shape of the land along one part of the map
ReliefDifference in elevation
Between any two pointsHighest elevation & lowest elevation
Relief Map
indicates elevation Shading, colors
topographic mapSpecial type of relief map
Calculating GradientsChange in the steepness of the slopeChange in elevation ÷ distance
Making Maps
Problem…
Earth is a sphere!Something (shape, distance or direction) is ALWAYS distorted
Accuracy
Depends on the size of the areaSmaller area, more accurate
Convert 3D to 2D with Map Projections
Map ProjectionsRepresentation of curved Earth shown on a flat surfaceMost accurate where paper touches globe3 basic types
Cylindrical (Mercator)Planar (Gnomonic)Conic
Mercator
Cylindrical projectionShows the whole world on a continuous map (except polar regions)Parallel latitude and longitude linesMost accurate around the equator
Or wherever paper cylinder touches globe
Distorted distances and shapesHigh latitudes are inaccurate
Conic ProjectionProject points and lines from a globe onto a coneCone touches globe at a particular line of latitudeOnly used for small areasMost accurate projection - nearly correct in all respects Useful in making
Topographic mapsRoad mapsWeather maps
Gnomonic Project points and lines from a globe onto a piece of paper touching the globe at a single pointshows shortest route between two points on the Earthuseful for planning airplane flights and ocean tripsproblem – directions and distances are distorted
Great Circles
Great circlesPlane passes through the center of the sphere
Small circlePlane does not pass through center of sphere
EquatorGreat circle
Each meridianHalf a great circle
Great Circle RouteShortest distance between two points on a sphereUsed for airplane travel
Special Projections
RobinsonGoode’s
Robinson ProjectionCombines the good parts of several other map projectionsMinimal distortion of most of the Earth's land masses
Antarctica & northernmost landmasses are still greatly distorted
Commonly considered the best map Commonly considered the best map representation of the size and shape of the representation of the size and shape of the Earth's landformsEarth's landforms
Goode’s oceans interrupted to show the continentstrue shape to continents
Remote Sensing
Collecting data about the Earth from far above the Earth’s surface
The Electromagnetic SpectrumArrangement of electromagnetic radiation according to wavelengthsAll travel at the speed of light in a vacuum
300 000 km/s
WavelengthDistance between two successive peaksGamma shortestRadio longest
FrequencyNumber of waves that pass a point per secondGamma = highestRadio = lowest
SatellitesLandsatTopex/poseidon
Global Positioning System (GPS)Sea Beam
Remote Sensing Techniques
Landsat Satellites
Receives reflected wavelengths of energy emitted by Earth’s surface
VisibleIR (infrared)
Used forEarth’s features (rivers, forests…)Movement of Earth’s platesEarthquakesPollution
Topex/Poseidon Satellite
Uses radar to map features on the ocean floor
Tidal currentsGlobal ocean currents
Uses echo to determine distance
Time from sent signal to received signal
The Geographic Positioning System (GPS)Radio-navigation system of 24+ satellitesHigh frequency microwaves Determine exact position on the Earth
Precise latitude & longitude
Other uses includeDetect earthquakesCreate mapsAirplane/ship navigationTrack wildlife
GPS satellites triangulate points on the Earth’s surface.
Using remote sensing satellites in space, the GPS system can locate points to within inches of its actual location.
Sea BeamUses sonar from a ship to map the ocean-floor features