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MAP SCALE
Scale varies across all maps
Pattern of scale distortion depends on map projection
Scale along line/point of SF = 1 (reference globe vs flat map) displayed in several ways:
Representative fraction, or simple scale1:100,000 or 1/100,000
Verbal statement – “One inch to 16 miles”
Bar Scale
Area Scale
REFERENCE SYSTEMS
Some common, familiar reference systems:
• Dewey Decimal system for libraries
• Street addresses used by postal service
• Road map grids used by Rand McNally, etc. on travel maps
• Zip Codes for area reference
• Area Codes used by phone company for area reference
COORDINATE SYSTEMS
Geographical coordinate system:
Older of two systems now in general use Uses latitude and longitude to locate positions on the uniformly curved surface of the earth Primary system – used for navigation and surveying
Rectangular/plane coordinate systems:
Used for locating positions on a flat map Evolved from cartesian coordinates applied to maps for for military purposes
COORDINATE SYSTEMS
Cartesian Coordinates:
Originally devised by armies for easier computation of artillery trajectories
Defined by origin and unit of distance – basically a graph
Depend on Euclidean geometry
COORDINATE SYSTEMS
Rectangular Coordinates:
o Based on Cartesian coordinate system
o Large scale maps typically use a conformal projection to maintain distance and direction calculations using rectangular coordinates
o False easting and northings are typically added to coordinate values to keep coordinates in the upper right hand quadrant of the ‘graph’ – positive values
o Most plane coordinate systems based on only these three conformal map projections: transverse Mercator, polar stereographic, Lambert’s conformal conic
o Not used for small scale maps – too much distortion
COORDINATE SYSTEMS
United States coordinate systems in common use:
• Universal Transverse Mercator Grid System
Topographic maps, satellite imagery, natural resourcedatabases, applications requiring precise positioning
Uses meter as basic unit of measure
Contains 60 narrow zones running N/S
SF constant only along NS meridian of each zone
Accurate overall to 1 part in 2500
COORDINATE SYSTEMS
United States coordinate systems in common use:
• Universal Polar Stereographic Grid System
Used to represent two circular polar zones not coveredby UTM system
SF is constant along parallels, which are circles inthis projection
Accurate overall to one part in 2500
COORDINATE SYSTEMS
United States coordinate systems in common use:
• State Plane Coordinate System
Devised in the 1930’s – plane rectangular coordinatesystem for each individual state
Based on transverse Mercator or Lambert’s conformalconic projections; line of constant SF depends onwhich projection used
Unit of measure is feet
Overall accuracy to one part in 10,000
COORDINATE SYSTEMS
United States coordinate systems in common use:
• Public Land Survey System
Basic unit is areal, not linear – acre
System is defined on the ground, not on a map grid
Currently covers ¾ of land in the 50 states
Baseline and meridian are defined on the ground andserve as origins
System defines township, range, section
Commonly used for legal descriptions of property
CARTOGRAPHIC DESIGN
Most design choices are compromises
Design as a process
Stage one – imagination, creativity, graphic ideation> decide on type of map, size and shape, basic layout, data to be represented, mapping technique, etc.
Stage two – specific graphic plan, most decisions made> kinds of symbolism, number of classes and class limits of data, color use, typographical relationships, line weights, etc. (often done on the fly using computers)
Stage three – detailed specifications> define all symbols and line weights, colors, lettering size, etc.
CARTOGRAPHIC DESIGN
• Design as a product
Does the map ‘look right’?
Should be clear, simple, uncomplicated, and elegant
Map should not look contrived
Map should be aesthetically pleasing, while at the same time being thought provoking
Does the map accurately and effectively communicate your message – the results of your data analysis?
WHO IS YOUR AUDIENCE?
CARTOGRAPHIC DESIGN
Basic Graphic Elements Point – position Line – direction and position Area – extent, direction, position
Primary Visual Variables Shape – regular/geometric or irregular/pictographic Size – length/height/area/volume – larger = more important Orientation – lines/elongated shapes – need reference Color (hue) – actual color (red, green, blue, etc.) Color (value) – tone or relative lightness/darkness
light = high value, dark = low value Color (chroma) – saturation/intensity/richness/purity
measured by how much gray is present
CARTOGRAPHIC DESIGN
From Robinson, Sixth Edition, page 320
The PrimaryVisual VariablesWith someExamples of theirSimple applicationTo the classes of symbols
CARTOGRAPHIC DESIGN
Types and symbols useful in quantitative mapping and their visual dimensions.
Courtesy JP Publications. From Dent, Fifth Edition, page 78.
CARTOGRAPHIC DESIGN
Secondary Visual Variables (pattern)
Arrangement – random or systematic shape and
configuration of component marks that make up a pattern
Texture – size and spacing of component marks that make
up a pattern
Orientation – direction arrangement of parallel rows of
marks or parallel lines that make up a pattern
CARTOGRAPHIC DESIGN
The Secondary Visual Variables with some examples of their simple application to the basicgraphic elements.
From Robinson, Sixth Edition, page 321
CARTOGRAPHIC DESIGN
Symbol Classes
Symbols should focus attention on what the symbol
represents, not what the symbol looks like
Point emphasizing symbols:
• Dots, triangles, pictographs
• Denote position, location of feature, intensity at a
place, representative location for spatial summary
• Examples: geographic coordinate location, radio
tower, spot height, centroid of area distribution,
conceptual volume (city population)
• Does not take up any geographical space
CARTOGRAPHIC DESIGN
Line Emphasizing Symbols
• Individual linear signs
• Depict rivers, roads, political boundaries
• Can also represent non-linear data such as
elevation/depth/volume – contour lines
• May or may not indicate actual geographical size of
features
CARTOGRAPHIC DESIGN
Area Emphasizing Symbols
• Indicate that region has some common attribute
• Examples include water, administrative jurisdiction,
soil type, other homogeneous measurable
characteristic
• Homogeneous nature depicted by even color or
uniform repetition of point or line symbols (pattern)
CARTOGRAPHIC DESIGN
Volume Emphasizing Symbols
• Represent vertical or intensity dimension of spatial
phenomenon through space
• Examples include terrain surfaces
• May be symbolized by color value (lightness)
variations, spot height data, profile or contour lines