Review Sheet for Exam 2 in Computer Mapping

This is a general list of items to know for Exam 2.
Disclaimer:  This list is not intended to be a complete itemization of all questions on this exam.  
However, knowing this material will serve as a good starting point in preparation for study.

Be able to identify, know the meaning of, or otherwise give examples of the following:

Map Projections
The age-old question . . .
·  Which is better?
·  The pros and cons of each?
·  View: Perspective / Orthographic?
Map Projections
Transforming the sphere to a plane
·  Ever peel an orange in one piece?
·  What exactly is a projection?
·  How many projections are there?
What aspects of reality do you most want to preserve in a map projection?
·  Area (equivalence)
·  Shape (conformality)
·  Distance
·  Direction
Projection Surfaces
How are map projections constructed?
Onto what surfaces are globes projected?
·  Cylinder
·  Plane
·  Cone (What is a Standard Parallel?)
The Mercator Projection
What is the history and controversy
surrounding this famous projection?
How does one choose a projection?
In this class you won’t be asked to create one but, in general . . .
·  For distribution maps, use equal area.
·  For navigation maps, use azimuthal.
·  For showing shapes, use conformal.
·  For small areas (large scale), pick one.
·  For large areas (small scale), it’s tricky.
Land-Partitioning Systems
How do we carve up Earth’s surface?
·  Metes and bounds (unsystematic)
 US Public Land Survey (systematic)
Types of Projections to Know:
Mercator
Sinusoidal
Azimuthal
Goode Interrupted Homolosine
What is meant by a Compromise Projection?
Robinson

Scale and Generalization Concepts
What is Scale?
·  Ratio between distance on a map and the actual distance in reality.
·  Scale determines resolution:
-- The smallest identifiable object on a map is directly tied to scale.
-- Resolution changes with scale and detail can be lost.
-- High resolution computer maps necessitate more storage space for more detail.
-- Scale chosen determines attributes and entities that will be emphasized.
What are the 3 Types of Scale?
·  Verbal (word)
-- “one inch equals one mile”
·  Graphic (linear or bar)
-- A visually read line segment.
-- But one must take care with precision.
·  Representative Fraction (RF)
-- 1:63,360
-- What is “special” about this scale?

Sample Scale Questions
Q:  If the RF on a map is 1:24,000 then what is the verbal scale in inches/feet?
A:  One inch equals 2,000 feet.

Q:  If the graphic scale of a map shows, by measurement, that one inch on the map equals two miles in the real world, then what is the RF?
A:  1:126,720

Large vs. Small Scale: it's all relative.
Instead, “larger” vs. “smaller” scales?
·  Be careful of confusion here.
Regarding scale, in general:
·  Small-scale maps show little detail but over a relatively large area.
·  Large-scale maps show lots of detail over a relatively small area.
1/24,000           Larger scale than 1:63,360, but it displays a smaller area, too.
1/100,000,000  Very small scale when compared to 1:63,360, yet can display whole Earth, though with little real detail.

Terrain Representation
Flat Earth?  No way!
How can maps show relief?
· Spot heights (bench marks)
· Water surfaces
· Contour lines - Interpolation
· Color tints
· Hill shading
· Physiographic diagram
· Block diagram
Terrain Representation
· Making a mountain out of a mole hill?
· How do you show 3-D landscape?
· Computer maps crude, but progressing.
· Early attempts?
Early attempts at Terrain Representation
· Mole hills ("sugar loafs")
· Hachures ("wooly worms")
Topographic Maps (pp. 130-136)
· Many useful purposes; such as?
Concept of contour lines.
Hypsometric tints: pros and cons?
--Relief shading
--Physiographic diagrams
--Inclined traces
Erwin Raisz
Profile diagrams
--unexaggerated vs. exaggerated
 

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