Representations of Locations and Patterns Locations Latitudes Longitudes
- Slides: 42
Representations of Locations and Patterns Locations, Latitudes, Longitudes, The Geographic Grid, Time Zones, Map Projections
Representations of Locations and Patterns • Being able to convey (or communicate) where things are, is essential to describing and analyzing aspects of Physical Geography. • A Map is essentially a communication device • Communicates spatial data/information through “graphic symbols” – a language of location (Appendix B in Text)
Emergence of Cartography – the art and science of mapmaking – increasingly an automated, computerized process Ø However, Maps and Mapmaking have evolved over the years, becoming increasingly more complex, sophisticated, automated, and ubiquitous Ø The challenge has always been to represent locations and patterns on earth accurately and efficiently
Maps have been in existence since time immemorial – simple maps of relative locations A Very Early Map Town Plan from Catal Hyük, Anatolia, Turkey, 6200 B. C. Reconstruction of Drawing
Early Maps � Clay tablets from Ga-Sur 2500 B. C. Interpretation of drawing
Early World Maps � The world according to Herodotus 450 BC
Early World Map � � Reconstruction of world map according to Dicaearchus (300 B. C. ) Early attempt to make locations more precise – Absolute Location
The first Lines of Parallels and Meridians Eratosthenes c 276 - 195 B. C.
Earth’s Dimensions : An Oblate Spheroid or Ellipsoid (Newton, 1687)
What does this suggest about the degree of “sphericity” of Earth? The flattening of the polar regions and the bulging of the equatorial region are too minor to be visible from space.
LATITUDE AND LONGITUDE Lines of Parallel equate to Latitude is measured from the Equator (00) to the Poles (900 N/S) Lines of Meridians equate to Longitude is measured from the Prime Meridian (00) to the International Date Line (1800 E/W) Both Latitudes and Longitudes are measured in angular distance from the center of the earth
Together, the Lines of Latitude and Longitude constitute the Geographic Grid Latitude ranges from 00 to 900 N/S Longitude ranges from 00 to 1800 E/W
Locating Los Angeles, California
Measuring Latitudes (a) Lines of Latitude – measured in angular degrees (°) from the center of the earth, North and South of the Equator Each Degree subdivided into Minutes (′), and Seconds (″) (b) Lines of Latitude – parallel and evenly spaced (hence, Parallels of Latitude)
Special Parallels and Global Latitudinal Zones Special Parallels: Equator (0◦), Tropic of Cancer (23 ½° N), Tropic of Capricorn (23 ½° S), Arctic Circle (66 ½° N), and Antarctic Circle (66 ½° S) → Latitudinal Zones
Measuring Longitudes Lines of longitude or meridians – non-parallel circular arcs that converge at the poles – measured in angular degrees (°) from the center of the earth, East and West of the Prime Meridian There are 180° of longitude on either side of the Prime Meridian – which is 0°, and starts at the Royal Observatory at Greenwich, London
Measuring Latitude/Longitude Distances � A degree of latitude represents a constant distance on the ground – approx. 69 miles or 111 km – from the equator to the poles � At the equator, a degree of longitude measures about 69 miles (111 km), at 40° N or S, 53 miles (85 km), and at the poles, 0 miles (0 km) � Sextants and Chronometers – used to measure latitudes and longitudes – now increasingly GPS
Great Circles & Small Circles Equator is a Great Circle: dividing the earth into two equal halves
Earth’s Rotation and Time: • Before 1884, “Local Time” based on Solar Noon • Now, we have Time Zones – Why? • In 1884, International Meridian Conference in Washington, D. C. established: a) Prime Meridian (through Greenwich) – GMT and Universal Time Coordinated (UTC) ↔ In 1972 became legal official time in all countries b) Time Zones – 24 Zones, 15 Degrees or 1 Hour apart, 7. 5 Degrees East & West of the Central Meridian of the respective zones
International Standard Time Zones
International Standard Time Zones
New World/North American Time Zones
Ø International Date Line: IDL Established in the 1880 s, and it follows the 180° meridian, with adjustments ü The International Date Line lies directly opposite the prime meridian, having a longitude of 180° ü Crossing the line traveling east, we turn our calendar back a full day (i. e. , gain a day); Traveling west, we move our calendar forward one day (i. e. , lose a day)
Latest Adjustment: Samoa & Cook Islands
Map Projections The challenge is to transfer a spherical grid (or the Geographic Grid) onto a flat surface
Visualizing the transfer of a spherical grid (or the Geographic Grid) onto a flat surface
Projections – Going from a Sphere to Flat Maps v Created by transferring points on the earth onto a flat surface. Like having a light in the center of the earth, shining through its surface, onto a projection screen (or, projection surface) v Projections now developed mathematically, using computer algorithms v There are three basic types of map projection: (Based on the presumed positioning of projection surface) 1. Cylindrical 2. Planar (or Polar or Zenithal) 3. Conic (or Conical)
Cylindrical Projection Cylindrical projection surface wrapped around the Earth; point of contact is equator Point of contact at equator
Cylindrical Projection: Mercator – A Conformal Projection Note increasing distance between lines of latitude…. why? Watch Video: http: //www. youtube. com/watch? v=AI 36 MWAH 54 s
Why Mercator? NAVIGATION! � In a Mercator projection, lines of longitude are straight vertical lines equidistance apart at all latitudes – so horizontal distances are stretched above and below the equator – more toward the poles � Mathematically stretches vertical distances by the same proportion as the horizontal distances so that shape and direction are preserved � Preserves what sailors in the 16 th century needed – shapes and directions; they were willing to accept size distortion � Any straight line drawn between two points on a Mercator Projection represents a “rhumb line” – it shows true compass direction
True Compass Heading: Rhumb Line in Mercator Projection was the navigation map of choice for sailing ships: good direction, even though longer route
Planar/Polar Projection Planar – (Polar, Zenithal) – projection surface is a ‘flat’ surface against the Earth at a particular latitude or longitude
Polar/Planar Projection centered on the North Pole
Polar Navigation? : GNOMONIC! ◦ Great circles are represented by straight lines, making it very useful in plotting Great Circle Routes between selected destinations � Gnomonic Maps are the navigational maps for the “Air Age” Gnomonic projections can be either “Conformal” or “Equal Area”, but not both
Conic Projection Conic (or Conical) – projection surface is a cone, placed on or through the surface of the Earth – Where the projection surface touches the earth is the “Standard Parallel (or Line)”
Conic Conformal Projection A better choice for mapping mid-latitude regions such as the United States is a conic projection. Locations near the line(s) where the cone is tangent to the Earth, the standard parallel(s), will be relatively free of distortion
Typology based on Projection Challenges q Distortion – It is impossible to flatten a spherical object without some distortion in its basic attributes or properties q Map Projections try to preserve one or more of the following properties: § Area – relative representation of area size on map (for small areas). Projections that preserve ‘area’ are “Equal Area” projections. § Shape – when meridians (longitude) and parallels (latitude) are made to intersect at right angles, shape is preserved locally. Projections that preserve “shape” for small sections are “Conformal. ” § Direction – or “azimuthality” – maintain cardinal directions (N, S, E, W). Projections that preserve “direction” are “Azimuthal. ” § Distance – variation in distance or scale on the same map ought to be minimized. Projections that preserve “distance” are “Equidistant. ” ü CONFORMAL vs. EQUAL AREA: Projections can be either conformal or equal area – but not both!
Compromise Projections The Robinson Projection is among the compromise projections that uses tabular coordinates rather than mathematical formulas to make earth features look the "right" size and shape. A better balance of size and shape results in a more accurate picture of high-latitude lands like Russia and Canada. Greenland is also truer to size but compressed. It was adopted by the NGS in 1988. https: //www. youtube. com/watch? v=wlf. LW 1 j 05 Dg
Compromise Projections Watch Video: – Interrupted Case
Transverse Mercator Projection Orthographic Projection https: //www. youtube. com/watch? v=v 5 f. SBQRb. PR 0
Registration & Alignment Problems When using multiple maps of the same area, using different projections Computer algorithms now adjust for these problems in GIS applications.
- Practice latitude and longitude
- Earth coordinate system
- Tema de medidas
- The lines of longitudes run from_________ to________ pole.
- Horse latitudes doldrums
- Horse latitudes
- Why is it called horse latitudes
- Horizontal lines on earth
- Lower latitude
- Single cell model of atmospheric circulation
- Horse latitudes doldrums
- Horse latitudes doldrums
- Elizabeth mulroney
- Wind notes
- Describe latitude
- Associations and correlations in data mining
- A day in pompeii vimeo
- Cultural representations and signifying practices
- Maps and plans grade 12
- Mathematical literacy grade 11 questions and answers
- Maps, plans and other representations of the physical world
- Elevation map grade 12 maths lit
- Functions and their representations
- Dating serves several important functions that include
- On single image scale-up using sparse-representations
- Nonlinguistic representation
- Marzano nonlinguistic representation
- Unit 1: media representations mark scheme
- Representations of a line
- Efficient estimation of word representation in vector space
- Distributed representations of words
- Isa written representations
- Pictorial flowchart
- Efficient estimation of word representation in vector space
- Connecting representations
- Multiple representations
- Multiple representations
- Representations of three dimensional figures
- Representations of functions as power series
- Character table of c3v
- 574 in expanded form
- Economics
- Multiple representations of polar coordinates