1. Introduction to Geography
Arthur Getis, Judith Getis, & Jerome D. Fellmann

2. Maps
Chapter 2

3. Overview The Grid System Map Projections Scale Types of Maps
Remote Sensing
Geographic Information Systems

4. The Grid System
Poles
Equator
Latitude
Longitude

5. Latitude Angular distance north or south of the equator
Measured in degrees
0°-90° North or South
Each degree of latitude = 111 kilometers (69 miles)
Slightly longer near the poles
Slightly shorter near equator
Minutes (’) & seconds (”)

6. Latitude (Continued) Prime Meridian Other meridians
Passes through the Royal Observatory at Greenwich, England
Selected at an International Conference in 1884
Other meridians
True N-S lines connecting the poles
Farthest apart at equator

7. Longitude Angular distance east or west of the Prime Meridian
International Date Line generally follows the 180th meridian
Distance between lines decreases towards the poles
Time depends on longitude
Each time zone ≈ 15° of longitude

8. Other Grid Systems Universal Transverse Mercator
Township & Range system
Land Ordinance of 1785
First used in eastern Ohio
36 mi2 divided in 36 squares of 1 mi2 (640 acres)
Divided into quarter sections of 160 acres
See Figure 2.4

9. Map Projections
Transforming a globe surface to a flat surface always results in distortion
Properties of Map Projections
Area
Shape
Distance
Direction

10. Area
Equal-area or equivalent projections represent areas in correct proportion to the earth’s area
But, the shape of the area is distorted to achieve this
See Figure 2.5

11. Shape
No map can provide correct shape for large areas, but some can accurately portray shapes for small areas
Maps that have true shapes are known as conformal
A map cannot be both conformal and equivalent (equal-area)

12. Distance Distance relationships are almost always distorted on a map
Some maintain true distances along one direction or along certain lines
Equidistant projections show true distances in all directions, but only from one or two central points
See Figure 2.9
A map cannot be both equidistant and equal-area

13. Direction
Directions between all points cannot be shown without distortion
Azimuthal projections enable a map user to measure the distance from a single point to any other point
Azimuthal projections may also be equivalent, conformal, or equidistant

14. Types of Projections “Developable Surfaces” Globe properties
All meridians are equal in length
All meridians converge at the poles
Lines of latitude are parallel to the equator and to each other
Parallels decrease in length as one nears the poles
Meridians and parallels intersect at right angles
The scale on the surface of the globe is the same everywhere in all directions

15. Cylindrical Projections
Mercator Projection
A lot of distortion towards the poles
Shapes are fairly accurate, but areas are widely distorted
Rhumb lines

16. Conic Projections The cone is closest in form to ½ of a globe
Conic projections are widely used to depict hemispheres or smaller parts of the earth
See Figure 2.8a

17. Planar Projections Plane tangent to the surface
Planar projections are equidistant from the tangent point
Commonly used for polar areas
Gnomonic projections show all great circles as straight lines
See Figure 2.10

18. Other Projections Goode’s Homolosine Robinson
Ovals, hearts, trapezoids, stars, etc.

19. Scale
Ratio between the measurement of something on a map and the corresponding measurement on the earth
Represented in three ways
Verbally
Graphically
Representative fraction (RF)
1:25,000 or 1/25,000

20. Scale (continued) Large-scale maps show a small area
Very detailed
Small-scale maps show large areas
Very generalized

21. Types of Maps Topographic Surface areas in relatively high detail
Physical & human features
USGS quadrangles
NRCAN in Canada
Contour lines & intervals
Shaded relief

22. Types of Maps (continued)
Thematic Maps
Point symbols
Dot density
Proportional circles
Area symbols
Usually different colors or patterns
Choropleth maps
Line symbols
Non quantitative, such as roads
Quantitative, such as isolines
Flow-line maps

23. Remote Sensing Detecting the nature of an object from a distance
Aerial photography
Orthophotomaps
False-color images
Nonphotographic imagery
Thermal scanners
Radar
Satellites

24. Satellite Imagery Landsat SPOT First launched 1972
Multispectral scanners (MSS)
Thematic mapper (TM)
SPOT

25. Geographic Information Systems (GIS)
Five major components
Data input
Data management
Data manipulation
Analysis functions
Data output