cs 128/es 228 - lecture 3a1 map types. cs 128/es 228 - lecture 3a2 two related hierarchies data...
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CS 128/ES 228 - Lecture 3a 1
Map Types
CS 128/ES 228 - Lecture 3a 2
Two Related Hierarchies Data Information Knowledge
Input Process Output
Question: When do we process the Data into Information or Knowledge?
CS 128/ES 228 - Lecture 3a 3
Early Processing Compute your answers early and
then reveal them when asked. Commonly done for systems such as
search engines
CS 128/ES 228 - Lecture 3a 4
Late Processing Store only your data; compute
answers as needed
MapQuest does this, as requests can’t be known in advance
CS 128/ES 228 - Lecture 3a 5
Hybrid Do some processing early, do some
late It is usually hard to detect that this is
happening “Caching” is one (not so good) example
of this approach.• (Not so good because caching isn’t really
processing, per se)
CS 128/ES 228 - Lecture 3a 6
About the Output GIS’s have two main types of output
Reports Maps
As always, these can be combined
CS 128/ES 228 - Lecture 3a 7
Reports A Geographic Information System is, at its
core, a database. Good database software always has a
report generator. Ergo, one can produce reports from a GIS
On the theory that we already know how to write well, reports are relatively uninteresting to us as students – however vital they may be to real world concerns
CS 128/ES 228 - Lecture 3a 8
Maps (and map types) The cartographer must make certain
fundamental decisions about what to include on the map.
Choices include Selection – what data to include Simplification – what data to combine Symbolization – how to show that data
CS 128/ES 228 - Lecture 3a 9
A Spectrum
How “processed” is the data?
Not at all Some Lots
Image Maps Line Maps Cartograms
CS 128/ES 228 - Lecture 3a 10
Image maps Composed of images of the area under
study (usually aerial photos)
Often pieced together to make “mosaics”
CS 128/ES 228 - Lecture 3a 11
Advantages of image maps
What you see is what is there (assuming the photo is current)
CS 128/ES 228 - Lecture 3a 12
Problems with Image Maps Interpretation
Details can be tricky – perspective is unusual
Distortion Especially near
edges and seams No annotation
CS 128/ES 228 - Lecture 3a 13
Line Maps Reality is replaced
by “reality-based” renderings
“Raw” data is replaced by a representation of that data
CS 128/ES 228 - Lecture 3a 14
Advantages of Line Maps Can concentrate
on information “of interest”
“Easy” to understand
CS 128/ES 228 - Lecture 3a 15
Disadvantages of Line Maps Data is not as
accurate due to: Incompleteness Representation
(especially scaling) Deliberate
“editorial” changes (see Exaggeration from previous lecture)
CS 128/ES 228 - Lecture 3a 16
Cartograms
Similar to line maps, but geographic data is deliberately distorted to make some other point
CS 128/ES 228 - Lecture 3a 17
Utility of Cartograms Strengths
Highlight exactly what is desired
Strong visual imagery
Weaknesses
Not useful outside initially intended domain
Relatively difficult to produce
Lots of information is lost
CS 128/ES 228 - Lecture 3a 18
Other types It is not uncommon to combine
some of these types
Cartographically Enhanced Image Maps are particularly common For example, the map we use in lab
CS 128/ES 228 - Lecture 3a 19
Map Forms
Historically, maps have been static, e.g. on sheets of paper
Computer technology has rendered maps dynamic, i.e. interactive
CS 128/ES 228 - Lecture 3a 20
Two “dynamic” maps
CS 128/ES 228 - Lecture 3a 21
Question To what degree do Quake and other
first person “shoot ‘em up” games provide “dynamic maps”?
What about the “maze” screen saver?
CS 128/ES 228 - Lecture 3a 22
Conclusions Many types of maps with varying
degrees of “reality” attached
There are tradeoffs between completeness of information and ease of user processing
The ultimate arbiter is the user
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