A map is almost universally a two-dimensional representation of a piece of three-dimensional space. Only with the advent of modern computer graphics were three-dimensional maps made possible. Maps serve two map functions; they are a spatial database and a communication device. The science of making maps is called cartography.
Basic map characteristics tell the reader where an object is (location) and what the object is (its attributes). Maps are also simplified reductions and abstracions of selected real world areas that have attributes of scale, resolution, and are defined onto a projection that distorts the curved surface of the earth onto a flat surface. Different objects represented on the map are classifed and symbolized so that the map user can easily use the map as a database of geographic information.
Every map has a scale, determining how large objects on the map are in relation to their actual size. A larger scale shows more detail, thus requiring a larger map to show the same area (a smaller number after the colon means a larger scale: 1:10,000 is a larger scale than 1:25,000).
Representing surfaces 1) contours 2) hill shading (shade from the north-west)
Other kinds of maps 1) morphometric maps – slope – aspect – roughness 2) terrain unit map – mountains – valleys – plains 3) Mimetic/Pictographic
The spatial resolution of a map is the size of the smallest feature on the map that can be correctly represented without distorting its relative size. Maps with a high resolution have more more pixels (detail) per unit area. The accuracy of a map is a measure of how close a mapped value is to reality. And map precision describes how fine the measurements are (2,145 kilometers is more precise than 2,100 kilometers).
If the map covers a large area of the earth’s surface, it also has a map projection, a way of translating the three-dimensional real surface of the globe to a two-dimensional picture. The most commonly used is the Mercator Projection; other popular projections are polar and a variety of equal-area projections.
Types of Maps
General reference maps are usually small scale maps that depict very large areas. A good example is an atlas. Thematic maps are used for special purposes such as showing the distribution of certain selected types of demographic or scientific data on a map that follows a theme. This is the main type of map that is made using GIS applications and is the result of performing some type of analysis. Charts are maps that represent the world in a way that are useful for navigational purposes. Plans are used by governments and buiders to layout construction projects (blueprints).
Maps covering parts of the earth tend to be either political or geographical. The most important purpose of the political map is to show national borders, and the purpose of the geographical is to show features of [[physical geography]]. Geological maps show not only the physical surface, but characteristics of the underlying rock, fault lines, and subsurface structures.
Cartographic Design Principles
To be an effective means in the conveyance of geographic data, maps must be legible, provide visual contrast between elements, have good figure to ground organization, must have a basis for differentiating elements, have a closed form, present familiar elements in recognizable ways and have a good contour interval (for topographic maps). Differences in detail should be expressed by using different element sizes and through hierarchical organization. There are three different categories of organization in maps; seterogramic, extensional and subdivisional.
Hierarchical organization – this is how you structure your map — stuff that is most important needs to stand out three types: 1) Stereogramic (color; brighter stands out, more saturate and lighter) 2) Extensional; used to show a ranking of symbols (thickness) 3) Subdivisional (states nested in countrys, countys nested in states)
Map design involves an exploration of the purpose of the map which includes the substantive purpose (logical goal: whether the needed data are presented) and the affective purpose (emotional goal: how the map is processed by the reader). The reality of map design has to deal with awkwardly shaped areas, areas on the map with overly dense data, data availability, the end user viewing distance (example: is this the map a wall map or a book map?), conditions of use (example: is this map going to be used in moist environment?) and technical limitations such as the amount of time alloted to make the map, its cost, and the ability of software to do accomplish the map’s goals.
The planning process in map design is an involved process. The cartographer must draw a preliminary sketch, help guide the layout decisions (desktop GIS layout tools make layout experimentation much easier), evaluate design options, develop several prototypes for review, find out if the map is a self standing product or will be part of a set, consider the number of copies that will be needed, and determine if the map will be folded or bound.
The optimal visual ratio of a map is about 3:5.
Contextual items included in a good map are a title, legend, source citation, map data, scale information, and a north arrow. A good map shouldn’t need to have the word “map” in the title since this is self-evident. It should also minimize verbiage, have a prominent but not huge title usually placed at he top of the map (unless the map in bound at the top) and also have the date that the map was made (unless the map is bound in a book). Disclaimers are often a matter of policy in many organizations so this may also be a requirement.
The map legend does not need to list all the elements and features of the map, but only the ones that are needed to affect its purpose. In addition, a properly constructed legond doesn’t need to have the word “legend” in its title and it is not necessary to have a box around a well-constructed legend. All maps should have some indicator of scale but the scale should be no more complex than needed to serve the map’s purpose. Since most maps are by convention oriented with the top of the map facing either grid, geographic or (less often) magnetic north, a north arrow is not too important and not needed at all if a distinct map grid is present.
Framing the Data and Map
All maps contain both neatlines and borders. A neatline demarks the limit of the mapped area and frames the data. Borders provide a frame for the map graphic and are usually outside the neatline but may be overlay it (meaning that the neatline and border form the same line).
Contextual elements (such as title, scale, legond etc.) are positioned relative to the neatline. In reference maps (such as a road atlas) the contextual elements go outside of the neatline so that information is not lost. In thematic maps it is common to place contextual elements in the parts of the map that do not contain data relevant to the map’s theme.
Most maps are now digitally produced and the mapmaker has to deal with dithering, different output devices, and color mismatching between what is displayed on the screen vs. what the output is on the printer. Different colors and patterns can be used to convey the information, qualitative vs quantitative color use has to be dealt with, along with color use conventions (such as blue meaning water), and thematic maps have to deal with color progressions. The use of color is dictated by what the map is going to be used for, and the kind of data that is to be presented.
Design objectives for quantitative use of color:
- correctly match map to legend
- give the impression of a progression of magnitudes
- allow for comparison between maps
The cartographer needs to know something about color theory which deals with how the different colors of the electromagnetic spectrum function in concert with the human eye and brain in the conveyance of information. The dimension of color is defined by its hue (what the color is), color saturation (its intensity and purity), and value (how bright the color is).
- Most important thing in legibility
- Four approaches:
- Single hue (only one color)
- bipolar (two colors)
- complimentary hue
- mixing with true colors on either end and a mix in the middle progressions of several hues
- good for elevations
Complements: Red/green, blue/yellow
Quantitative use of color
- the magnitude message
- Darker is more
Categories of color progressions
- single hue: vary saturation and value
- two hues: neural volor in venter to two dark endpoint hes.
- Progression of sevral hues
- value progresion: Shades of gray
Single hue progresson
- hold hue constant
Two hue progression (Bipolar verson)
- Same principle as single hue progression but with two endpoint hues. The center legend body is white.
Comlementary hue version
- End point hues are complemenary colors. The center legend body is neutral
Several hues: Partial spectral hue progression
- construct a progression using a part of the ROY G BIV progression
Blended hue progression
- Use colors not in the spectrum
Sybolic connotation of color
- hot vs. cool
- wet vs. dry
- bright vs. dark
- stop vs. go
Number of step is a progression
- Depends on the distribution of the data and complexity of map pattern
- Similar in concept to color progressions
- Denser and bolder patterns indicate higher magnitude.
- Avoid use of long, straight lines.
Qualitative use of color
- Use differnt hues to depict differences in kind.
- Use differnt shades of the same hue to depict different varieties of the same
Placing text on color
- Reverse the color of the text
Color conventions: Water is blue. Green is vegetation. Brown is land. Yellow is indicator of dry.
There are two main types of symbolizing symbols; quantifying symbols that give a visual measure of the relative size/importance/number that a symbol represents and qualifying symbols which represent different classes of objects with distinct types of symbols.
Basic graphic elements: points, lines and polygons
Classes of symbols
- point emphasizing
- line emphasizing
- area emphasizing
The measurement level used in maps is either nominal (names), ordinal (ordering relationships), interval (the distance between objects) or ratio.
Dimensionality of data
- zero dimensional (point)
- one dimensional (line)
- two dimensional (polygon)
- three dimensonl (volume)
This can be done wih a single hue progession where the low values are light and the high values are dark.
Two hues: neutral color in center to two dark endpoint hues
- Progression of several hues (elevation maps)
- Value progression: shades of gray
Nominal symbols (qualitative)
- use different hues or shapes or orientations
Ordering symbols (quantitative)
- Size, saturation/value
- Bigger is more, more saturated is more
Mimetic pictograh vs. geometric symbols Symbolizing feaue attribute volumes
Statistical surface: Mathematically continuous distribution over an area.
- Measurement scale may be:
Functions: locative, nominative and ordinal Elements of text: size, color, style, form Style: Font (serif or sans-serif) Form: Bold, italic, case, underline
Don’t want to use more than two styles.
Form conventions: Use uppercase sparingly (water bodies, or widely spaced lettering). Lowercase is easier to read. Italics is used for water (gives the indication of flow).
Size conventions; no smaller than 5 points. Use the largest text that doesn’t crowd the map.
Use text size to set up hierarchies.
Use color to link text with features.
text is all on the land or all on the water. If you can see the curvature of gradicule then align the text to it.
If needed repeat the names of things is they are long (such as river)
- lettering the map
- function of text on maps
- locative function
- ordinal (hierarchy)
Elements of typography
- type style
- type form
- type size
- type color
- two major categories
- serif (bubbles and styles)
- sans serif (straight)
- two categories of serif type
- classic or old style (goudy)
- modern (century schoolbook)
- both Serif styles are often called Roman
San serif styles are sometimes called Gothic
Style conventions for text
- use at most two style
- one serif and one sans serif
- have some rational for their use
- case UPPER CASE
- lower case
- Proper Case
Slant or italic
- don’t use tos as models for sizing text
- never use text smaller than 5 pt.
- set up hierarchy ontext size
general rules for positioning text
- entirely on land or entirely on water
- align oriented text with the graticule when curvature of the graticule is
- all disoriented text should have a slight cure
- when text is disoriented and widely spaced use all capital letters
- interrupt lines and patterns for type
- never let text flip upside down
- lower left jstification (words to upper right(
- second choice – upper left
- third choice
5 2 1 4 3 6
- label above line when possible
- read as horizontally as possible
- don’t space pars of nammes too widel
- avoid complex curves
Because maps are abstract representations of the world they are not neutral documents and must be carefully interpreted.
- David Buisseret, ed., ”Monarchs, Ministers and Maps: The Emergence of Cartography as a Tool of Government in Early Modern Europe.” Chicago: University of Chicago Press, 1992, [ISBN 0226079872]
- Mark Monmorier, How to Lie with Maps, [ISBN 0226534219]