What is a map?

What are maps & what are they used for? CS 128/ES 228 - Lecture 2a 1 Early mental maps are egocentric CS 128/ES 228 - Lecture 2a 2 Where would you like to live? CS 128/ES 228 - Lecture 2a

3 The geocentric map concept Based on: four cardinal directions angles and distances Directions to campus 1. It is easiest to approach campus from Route 17

(now called I-86). Take exit 24 (marked "Allegany - St. Bonaventure University"). At the end of the ramp, turn south (left if coming from Rt. 17 West, right if from Rt. 17 East). Drive about 1/2 mile to a "tee". 2. At the tee, turn left onto Route 417. Drive just over 2 miles, through the village of Allegany and across a high bridge over railroad tracks. Campus is visible to the right. 3. Immediately at the end of the bridge take the

first right onto College Road (if you get to the traffic light, you've gone slightly too far. Turn around and return to College Road). Take the second left into a the parking lot marked at the bottom of the map. CS 128/ES 228 - Lecture 2a 4 What is a map? Art is a lie which makes us realize the truth. P. Picasso

So is a map. P. Muehrcke (Map Use. 2nd ed. 1986) A map is a spatial model, an attempt to depict selected aspects of a geographic region on a flat plane. T. Georgian CS 128/ES 228 - Lecture 2a 5

Warning!!! Map and reality are not, cannot be identical. No aspect of map use is so obvious yet so often overlooked. Most map reading mistakes occur because the user forgets this vital fact and expects a one-to-one correspondence between map and reality. P. Muehrcke Map Use (p. 19) CS 128/ES 228 - Lecture 2a 6 How does a map differ from reality?

Size Dimensionality Amount of detail Symbolic presentation

Static vs. dynamic ??? CS 128/ES 228 - Lecture 2a 7 What about aerial photographs? Arent they equivalent

to reality? CS 128/ES 228 - Lecture 2a 8 Cartography: the art & science of creating maps CS 128/ES 228 - Lecture 2a 9 4 steps of cartography: 1. Selection

3. Exaggeration 2. Simplification 4. Symbolization For my part of this course, learn outlines!! See textbook, Box 2.3 (p. 27) for a different list CS 128/ES 228 - Lecture 2a 10

1. Selection Depends on: Purpose Data availability Size and scale of map CS 128/ES 228 - Lecture 2a 11

Selection: scale One of the most important choices determines what can or cannot be included in the map (Wheres SBU?) CS 128/ES 228 - Lecture 2a

12 Representing a maps scale Scale line ex. Scale ratio ex. 1:24,000

Verbal scale ex. 1 inch equals 2000 feet (often used with mixed units) Coverage ex. 7 minute topographic quadrangle CS 128/ES 228 - Lecture 2a 13

Large and small scales Large scale: Scale ratio is a large fraction a given feature looks large Small scale: Scale ratio is a small fraction

a given feature looks small CS 128/ES 228 - Lecture 2a 14 The dilemma of scale Small scale maps lack detail Large scale maps lack range (coverage) The dilemma can be alleviated somewhat by:

- locator maps-- - inset maps CS 128/ES 228 - Lecture 2a 15 Inset maps Great invention, but: User must deal with multiple scales

Rule: the inset always ends just short of the point of interest CS 128/ES 228 - Lecture 2a 16 Selection: coverage State maps minimize details in adjacent

states Topographic maps omit detail in urban areas CS 128/ES 228 - Lecture 2a 17 Selection: time frame

Maps are essentially snapshots Two rules: 1. Every map should be dated!! 2. Dont trust the dates CS 128/ES 228 - Lecture 2a 18 2. Simplification

Begins with choice of scale Other issues: Reduced dimensionality of line or area features Smoothing lines and boundaries Aggregation CS 128/ES 228 - Lecture 2a 19 Reduced dimensionality CS 128/ES 228 - Lecture 2a

20 Smoothing lines and boundaries The blues lines are from a digitized U.S.G.S. 7 min. topographic map. Note how the channel of Fourmile Creek been smoothed. CS 128/ES 228 - Lecture 2a 21 Aggregation Like smoothing, but refers to scale of

spacing of objects Depends not only on scale but also on purpose of map CS 128/ES 228 - Lecture 2a 22 3. Exaggeration Why, given scale limitations, would

map makers make features or labels larger? Make symbols visible Separate features and symbols CS 128/ES 228 - Lecture 2a 23

3. Exaggeration Exaggeration also reflects a maps purpose Saul Steinbergs Mar. 29, 1976 cover of the New Yorker magazine http://www.totalmedia.com/images/Newyorker.jpg CS 128/ES 228 - Lecture 2a 24 4. Symbolization

1. Size, texture, and density CS 128/ES 228 - Lecture 2a 25 Issues of Symbolization 1. Size, texture, and density

Which symbols are emphasized on this map? Why? CS 128/ES 228 - Lecture 2a 26 Issues of Symbolization 1. Size, texture, and density http://blogjunky.blogspot.com/populationmap.gif

http://www.atsdr.cdc.gov/HEC/HSPH/v5n21.jpg CS 128/ES 228 - Lecture 2a 27 Issues of Symbolization 2. Use of color CS 128/ES 228 - Lecture 2a 28

Issues of Symbolization 3. Realistic vs. abstract CS 128/ES 228 - Lecture 2a 29 Symbolization What decisions does this map reveal about: Size, texture, and

density Use of color Realistic vs. abstract symbols CS 128/ES 228 - Lecture 2a 30

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