CS 128/ES 228 - Lecture 3a 1

Map Types

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Two Related Hierarchies Data Information Knowledge

Input Process Output

Question: When do we process the Data into Information or Knowledge?

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Early Processing Compute your answers early and

then reveal them when asked. Commonly done for systems such as

search engines

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Late Processing Store only your data; compute

answers as needed

MapQuest does this, as requests can’t be known in advance

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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)

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About the Output GIS’s have two main types of output

Reports Maps

As always, these can be combined

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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

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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

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A Spectrum

How “processed” is the data?

Not at all Some Lots

Image Maps Line Maps Cartograms

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Image maps Composed of images of the area under

study (usually aerial photos)

Often pieced together to make “mosaics”

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Advantages of image maps

What you see is what is there (assuming the photo is current)

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Problems with Image Maps Interpretation

Details can be tricky – perspective is unusual

Distortion Especially near

edges and seams No annotation

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Line Maps Reality is replaced

by “reality-based” renderings

“Raw” data is replaced by a representation of that data

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Advantages of Line Maps Can concentrate

on information “of interest”

“Easy” to understand

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Disadvantages of Line Maps Data is not as

accurate due to: Incompleteness Representation

(especially scaling) Deliberate

“editorial” changes (see Exaggeration from previous lecture)

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Cartograms

Similar to line maps, but geographic data is deliberately distorted to make some other point

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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

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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

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Map Forms

Historically, maps have been static, e.g. on sheets of paper

Computer technology has rendered maps dynamic, i.e. interactive

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Two “dynamic” maps

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Question To what degree do Quake and other

first person “shoot ‘em up” games provide “dynamic maps”?

What about the “maze” screen saver?

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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