what are maps & what are they used for?

CS 128/ES 228 - Lecture 2a 1

What are maps & what are they used for?

CS 128/ES 228 - Lecture 2a 2

Early mental maps are egocentric

CS 128/ES 228 - Lecture 2a 3

Where would you like to live?

CS 128/ES 228 - Lecture 2a 4

The geocentric map conceptBased on: four cardinal

directions

angles and distances

Directions to campus1. 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 5

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 6

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 7

How does a map differ from reality? Size

Dimensionality

Amount of detail

Symbolic presentation

Static vs. dynamic

???

CS 128/ES 228 - Lecture 2a 8

What about aerial photographs?Aren’t they equivalent

to reality?

CS 128/ES 228 - Lecture 2a 9

Cartography: the art & science of creating maps

CS 128/ES 228 - Lecture 2a 10

4 steps of cartography:

1. Selection

2. Simplification

3. Exaggeration

4. Symbolization

See textbook, Box 2.3 (p. 27) for a different list

For my part of this course, learn

outlines!!

CS 128/ES 228 - Lecture 2a 11

1. Selection

Depends on: Purpose

Data availability

Size and scale of map

CS 128/ES 228 - Lecture 2a 12

Selection: scale One of the

most important choices – determines what can or cannot be included in the map (Where’s SBU?)

CS 128/ES 228 - Lecture 2a 13

Representing a map’s scale

Scale ratio ex. 1:24,000

Verbal scale ex. 1 inch equals 2000 feet (often used with mixed units)

Coverage ex. 7 ½ minute topographic quadrangle

Scale line ex.

CS 128/ES 228 - Lecture 2a 14

Large and small scalesLarge 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 15

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 16

Inset maps

User must dealwith multiplescales

Rule: the insetalways ends justshort of the point of interest

Great invention, but:

CS 128/ES 228 - Lecture 2a 17

Selection: coverage State maps minimize

details in adjacent states

Topographic maps omit detail in urban areas

CS 128/ES 228 - Lecture 2a 18

Selection: time frame Maps are essentially

snapshots

Two rules:

1. Every map should be dated!!

2. Don’t trust the dates

CS 128/ES 228 - Lecture 2a 19

2. SimplificationBegins with choice of scale

Other issues: Reduced dimensionality of line or area features Smoothing lines and boundaries Aggregation

CS 128/ES 228 - Lecture 2a 20

Reduced dimensionality

CS 128/ES 228 - Lecture 2a 21

Smoothing lines and boundaries

The blues lines are from a digitized U.S.G.S. 7 ½ min. topographic map. Note how the channel of Fourmile Creek been smoothed.

CS 128/ES 228 - Lecture 2a 22

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 23

3. ExaggerationWhy, given scale

limitations, would map makers make features or labels larger?

Make symbols visible

Separate features and symbols

CS 128/ES 228 - Lecture 2a 24

3. ExaggerationExaggeration also reflects

a map’s purpose

Saul Steinberg’s Mar. 29, 1976 cover of the New Yorker

magazinehttp://www.totalmedia.com/images/Newyorker.jpg

CS 128/ES 228 - Lecture 2a 25

4. Symbolization1. Size, texture,

and density

CS 128/ES 228 - Lecture 2a 26

Issues of Symbolization1. Size, texture,

and density

Which symbols are emphasized on this map? Why?

CS 128/ES 228 - Lecture 2a 27

Issues of Symbolization1. Size, texture,

and density

http://www.atsdr.cdc.gov/HEC/HSPH/v5n21.jpg

http://blogjunky.blogspot.com/populationmap.gif

CS 128/ES 228 - Lecture 2a 28

Issues of Symbolization2. Use of color

CS 128/ES 228 - Lecture 2a 29

Issues of Symbolization3. Realistic vs. abstract

CS 128/ES 228 - Lecture 2a 30

SymbolizationWhat decisions does

this map reveal about:

Size, texture, and density

Use of color

Realistic vs. abstract symbols