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Surface of earth of interest to geographers

Maps are a great tool to help understand and analyze the earth's surface

Today:

• describe basic characteristics of maps
  
• computers and new kinds of mapping

1. The Nature of Maps

Map: a two dimensional representation of the spatial distribution of selected phenomena; usually components of the human or physical landscape

A scaled drawing of a portion of a landscape, representing the area at reduced scale and showing only selected data

McKnight fig 2.1: Different kinds of maps

• 2.1a: Orthophoto map
  
• 2.1b: Historical Thematic Map (Nile)
• 2.1c: Road Reference Map (NYC)
• 2.1d: Geologic Thematic Map (Western US)

• Oddens' Bookmarks: The World of Maps and Mapping

1a. A Matter of Scale

Map scale

• the relationship between the map and the area portrayed
• size of an object on a map compared to the actual object on the ground

• Science Center: 1000 feet long on the ground, and 1 inch long on a map
• the map scale is: 1 inch = 1000 feet

• Google Maps
• Yahoo! Interactive Maps

Maps are almost always smaller than the portion of the Earth's surface they portray

Lewis Carroll "Sylvie and Bruno Concluded"

"What do you consider the largest map that would be really useful?"

"About six inches to the mile."

"Only six inches!" exclaimed Mein Herr. "We very soon got to six yards to the

mile. Then we tried a hundred yards to the mile. And then came the

grandest idea of all! We actually made a map of the country on a scale

of a mile to a mile!"

"Have you used it much?" I enquired.

"It has never been spread out, yet," said Mein Herr: "the farmers objected: they

said it would cover the whole country and shut out the sunlight! So we

now use the country itself, as its own map..."

Map Scale Types

• McKnight fig 2.3: map scale examples

Graphic scale: line or bar on map represents some set distance

• example

Word scales: describes the scale of the map in words

• example

Fractional scales: representative fraction: a proportion between map distance and Earth distance

• 1:100,000: representative fraction
  
• one unit on the map = 100,000 units on the ground

• Science Center: 1000 feet long on the ground, and 1 inch long on a map
• the map scale is: 1 inch = 1000 feet
• 12 inches in a foot, so [1000 x 12] = 12,000
• so the map scale is also 1 inch = 12,000 inches
• since the units (inches) are the same, drop them
• you get the representative fraction scale of the map: 1:12,000
• any 1 unit on the map (meters, yards, etc.) = 12,000 of the same units on the ground

Large and Small Scale Maps

McKnight fig 2.3: comparing map scales

Large scale / Small scale distinction is based on the representative fraction

• large scale maps have a relatively large representative fraction compared to small scale maps:
  • 1:1000 = .001 is larger scale
  • 1:10,000 = .0001 is smaller scale

• small scale maps: maps at 1:10,000,000 (or 'smaller') not much detail, generalized

• large scale maps: typically lots of detail; state size on a page or more detail

1b. Map Graticule

Necessary to have a means of locating phenomena on the earth and on maps

McKnight fig 1.17: latitude / longitude

1c. Map Projections

Globes have the least distortion from the actual earth

Problem: have to flatten out the Earth to get it on a flat surface

• known as the map projection process

• introduces all sorts of distortions

Image courtesy of Lilla Locurto and Bill Outcault

Inevitable distortions occur when you project a map

• McKnight fig 2.9: interrupted projection: rip the earth apart

Always some kind of distortion: of size, shapes, ...

McKnight fig 2.10: conformal vs equivalent map projections

• conformal: preserves shapes, but distorts sizes
• equivalent: preserves sizes, but distorts shapes

1d. Map Generalization: using judgement in the elimination of detail and reduction of the number of features on the original map

Mark Monmonier: "Reality is three-dimensional, rich in detail, and far too factual to allow a complete yet uncluttered two-dimensional graphic scale model. Indeed a map that did not generalize would be useless." (How to Lie With Maps)

• Google Maps
• Yahoo! Interactive Maps

1e. Map Content: reference vs. thematic

reference maps: general use (for many purposes), focus on and emphasize the location of things in the environment - many different purposes; like a general world atlas or encyclopedia

• McKnight fig 2.1: Reference road map

• U.S. Census Reference Maps

thematic maps: particular use or theme: focus on and emphasize the spatial patterns of one or several human or environmental phenomenon

• McKnight fig 2.1: Thematic geologic map

• U S Census Thematic Maps

1f. Map Symbolization

symbol: A thing representing something else because of relationship, association, convention, or resemblance.

Special Map Symbol: Isolines

• line symbols on maps which represent the spatial distribution of phenomena

• isoline: a line that joins points of equal value of something

• McKnight fig 2.12: topo map (contours): terrain surfaces
  

  
  

  Delorme Contour Map examples

  McKnight fig 2.13a: precipitation isolines (Africa)

  McKnight fig 2.13b: population isolines (S. America)

Basic characteristics of isolines

• always closed
  
• they never cross or touch or overlap
  
• they have a contour interval: ex) each contour is 20 feet difference in elevation
  
• the closer together: the steeper the gradient; the further apart, the gentler the gradient

2. Developments in Mapping: Computer aided Mapping

2a. Global Positioning System (GPS)

McKnight fig 2.16: 24 satellites around Earth, transmitting positioning information back to earth

GPS Orbits

2b. Remote Sensing

Remote sensing: any measurement or acquisition of information by a recording device that is not in physical contact with the Earth's surface

Aerial Photographs

• McKnight fig 2.18: oblique vs vertical: the angle of the remotely sensed image: from above, or from the side

• Clintonville OH Air Photo

Multispectral Remote Sensing

Increasingly: remote sensing (airplane, satellite) sensors gather energy (passively, or actively) from different parts of the electromagnetic spectrum

• McKnight fig 2.21: the electromagnetic spectrum

• example: Color and Color Infrared Sensing (Airplane and Satellite)

• McKnight fig 2.23: Color IR shot of Mississippi River Valley

• EarthShots

• NASA Remote Sensing

• EROS Imagery

• Remote Sensing Sites

• example: Thermal Infrared Sensing: sense the radiant temperature of objects

• example: Microwave Sensing

• example: Radar and Sonar Sensing

2c. Geographic Information Systems: GIS

Computer hardware and software for the capture, storage, retrieval, analysis, and display of spatial data

GIS is basically digital maps linked to digital databases

McKnight fig 2.29: layers which can be linked together in a coordinate system (lat/long)

• ArcView GIS Demo ???

Sum...

Six basic map attributes of all maps - paper or digital

• map scale
• map graticule
• map projection
• map generalization
• map content
• map symbolization

Developments in mapping

• Global Positioning Systems (GPS)
• Remote Sensing
• Geographic Information Systems (GIS)

Much more on all this stuff in Geography 222: The Power of Maps

• for us, maps will primarily be means to an end: understanding the earth

E-mail: jbkrygier@owu.edu

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