Transcript The Round Earth to Flat Map

Geography: Methods and Materials
Lecture 1: True Maps, False Impressions
Describe basic characteristics of maps,
 Describe various ways landscapes are portrayed

I. The Nature of Maps
A.
Map : two dimensional representation of the spatial distribution
B.
Basic attributes of maps, making them indispensable:
of selected phenomena ...


C.
Their ability to show distance, direction, size, and shape in two dimensional
spatial relationships
They depict graphically what is where and are helpful in providing clues as to
why such a distribution occurs.
Basic fault of a map?


D.
No map can be perfectly accurate, why?
Maps are trying to portray the impossible – taking a curved surface and
drawing it on a flat piece of paper
The matter of scale


Gives relationship between length measured on map & corresponding distance
on the ground, essential for being able to measure distance, determine area,
and compare sizes.
Scale can never be perfectly accurate (Earth’s curved surface)
o
Smaller area being mapped, the more accurate the scale…
Location
 Location
a) Absolute location (grid system)
latitude / parallel lines
longitude / meridians
b) Relative location
I. The Nature of Maps
E. Scale types

1.
Several ways to portray scale, but only 3 widely used:
Graphic scale:
a.
b.
2.
Word scale:
a.
3.
uses a line marked out in graduated distances
Remains correct when reproduced in other sizes
also called verbal scale; uses words to give the ratio of map scale
to actual distance
Fractional scale:
a.
b.
c.
Uses a ratio or fraction, called a representative fraction, to
express the comparison of map distance with ground distance
Scale 1/63,360 is commonly used; 1 in = 1 mile
Can use any units for the ratio
I. The Nature of Maps
F. Large and small scale
1.
The concepts of large and small are
comparative, not absolute, it all depends on the
frame of reference.
2. Large-scale map – has a relatively large
representative fraction; denominator is small
3. Small-scale map – has a small representative
fraction, the denominator is large
a.
Portrays large portion of Earth’s surface, but gives
limited detail.
II. The Role of Globes
A. Globes have several advantages:
1.
2.
3.
Can maintain correct geometric relationships
of meridian to parallel, of equator to pole, of
continents to oceans,
Can show comparative distances, comparative
sizes & accurate directions,
Can represent without distortion the spatial
relationships of features on Earth’s surface.
Globe properties

Parallels of latitude



Meridians of longitude


•
parallel to each other
decrease in length closer to the poles
converge at the poles
equal length (1/2 equator)
Both: intersect at right angles
World from Space
III. Map Projections
A.
B.
C.
D.
Process of transferring the spherical earth onto a
2-dimensional surface.
Estimate size and shape of earth in 3 dimensions
Properties of map projections:
 equal area (area)
 conformal (shape)
 equidistant (distance)
 azimuthal (direction)
Types of map projections:
 cylindrical
 conic
 azimuthal (planar)
III. Map Projections
E.
1.
Major problem: Equivalency vs. Conformality
Central problem in choosing a projection?
a)
Impossible to perfectly portray size & shape so compromise
between Equivalency & Conformality
1)
2)
b)
Can only approximate Equivalency & Conformality in maps of of
very small areas (large scale maps)
1)
2.
Map making is art of compromise (Robinson projection)
Equivalent projection: equal area:
a)
3.
Equivalence: property of map projection that maintains equal area
relationship
Conformality: property of map projection that maintains proper
angular relationships
Disadvantage: small scale maps display disfigured shapes
Conformal projection: equal shape:
a)
Disadvantage: distort size – larger sizes in high latitudes
III. Map Projections
Mercator projection
Transverse Mercator
Albers conic (equal area)
Azimuthal
Peters projection (equal area)
Robinson projection
Projections: Implications

Projection should suit the application:
Direction important? Conformal
• Comparing areas? Equivalent
•
IV. Automated Cartography
A. Computer technology has provided several
great benefits to cartography:
•
•
•
Improved speed and data handling ability,
Reduced time involved in map production,
Ability for cartographer to examine
alternative maps layout.
Global Positioning System
A. Satellite system for determining accurate
positions on Earth’ surface. 24 satellites
transmit position information (clocks)
•
•
Most GIS accurate to about 30 feet
Used in earthquake prediction, ocean floor
mapping, volcano monitoring, and mapping
projects.
VII. Geographic Information Systems
GIS is an abbreviation for
Geographic Information System,
which are...
automated systems for the capture, storage,
retrieval, analysis, and display of spatial data,
or
computer mapping & analysis of geographic
data
 Links tabular data to maps

GIS involves working with layers of spatial
data superimposed on one another
What Are the Components
of a GIS?
•
•
•
•
•
Hardware
Software
Data
Methods
People
VIII. Remote Sensing
A.
Study of the Earth’s surface from a distance
1.
recording instruments operating from high altitude
a)
Different kinds of remote sensing
1)
Aerial photos, color & infrared sensing, thermal infrared sensing,
microwave, SPOT
B.
Aerial Photographs
1.
First form of remote sensing
Aerial photograph: photo taken from elevated
platform such as balloon, rocket, airplane, satellite
2.
a)
Either oblique or vertical
1)
2)
Oblique: Angle less than 90 degrees
Vertical: camera angle perpendicular
a)
photogrammetry
VIII. Remote Sensing
C.
Orthophoto Maps
1.
Multicolored distortion free photographic
maps produced from computerized
rectification of aerial imagery.
a)
b)
Landscape in detail
Precise measurement of distance, shows subtle
topographic detail
D. Color infrared
1.
Color – visible light region of EM spectrum
a)
b)
Evaluate health of crops & trees
Landsat – satellites image Earth every 9 days