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Making Maps with GIS
Key Terms

area qualitative map: A type of map that shows the existence of a geographic class within areas on the map. Colors, patterns, and shades are generally used. Examples are geology, soils, and land-use maps.

border: The area between the neat line and the edge of the medium or display area on which a map is being displayed. Occasionally, information can be placed within the border, but this area is usually left blank.

cartographic convention: The accepted cartographic practice. For example, water is usually cyan or light blue on a world map.

cartographic elements: The primitive component part out of which a map is assembled, such as the neat line, legend, scale, titles, figure, and so on.

choropleth map: A map that shows numerical data (but not simply "counts") for a group of regions by (1) grouping the data into classes, and (2) shading each class on the map.

clarity: The property of visual representation using the absolute minimum amount of symbolism necessary for the map user to understand map content without error.

color balance: The achievement of visual harmony between colors on a map, primarily by avoiding colors that show simultaneous contrast when adjacent to each other.

contour interval: The vertical difference in measurement units such as meters or feet between successive contour lines on a contour map.

contour map: An isoline map of topographic elevations.

credits: A cartographic element in which the sources, authorship, and ownership of the map and the map attributes are cited, often including a date or reference.

design loop: The iterative process in which a GIS map is created, examined for design, improved, and then replotted from the modified map definition until the user is satisfied that a good design has been reached.

dot map: A map type that uses a dot symbol to show the presence of a feature, relying on a visual scatter to show spatial pattern. Most often used where point features are the GIS data, but dots can be scattered at random throughout areas.

figure: The part of a map that is both referenced in the map coordinate system rather than the page layout coordinates and that is the center of the map reader’s attention. The figure is contrasted against the ground, or background. For example, on a map of New York State, the state is the figure, and surrounding states, though shown and labeled, are part of the ground and may be toned down.

flow map: A linear network map that shows, usually by proportionally varying the width of the lines in the network, the amount of traffic or flow within the network.

fonts: A consistent design for the display of the full set of English or other language characters, including special characters such as punctuation and numbers.

graduated symbol map: A map type that varies the size of a common geometric symbol to show the amount of an attribute at points or at centroids of areas. For example, cities could be shown with circles of area proportional to population, or census tracts could have a proportional circle divided as a pie chart at a representative point inside the tract.

gridded fishnet map: A map of a three-dimensional surface showing a set of profiles, often parallel to the x, the y, or the viewer’s axis so that the surface appears three-dimensional, as a raised fishnet viewed in perspective.

ground: The part of the body of the map that is not featured in the figure. This area can include neighboring areas, oceans, and so on. The ground should fall lower than the figure in the visual hierarchy.

harmony: The property by which the elements of a map work together to create a balanced aesthetic whole.

HSI: A system for color, specified as values for hue, saturation, and intensity, respectively.

hue: A color as defined by the wavelength of the light reflected or emitted from the map surface.

hypsometric map: A map of topography involving a color sequence filling the spaces between successive contours, usually varying from green through yellow to brown.

image map: A map that in two dimensions shares many of the characteristics of a map, that is, cartographic geometry, some symbols, a scale and projection, and so on, but is a continuous image taken from an air photo, a satellite image, or a scanner. A scanned paper map used as a backdrop in a GIS becomes an image map.

inset: A map within a map, either at a smaller scale to show relative location, or a larger scale to show detail. An inset may have its own set of cartographic elements, such as a scale and graticule.

intensity: The amount of light emitted or reflected per unit area. A map that has high intensity appears bright.

isoline map: A map containing continuous lines joining all points of identical value.

label: Any text cartographic element that adds information to the symbol for a feature, such as the height number label on a contour line.

label placement rules: The set of rules that cartographers use when adding map text, place names, and labels to features. Some rules are generic to the map as a whole, while others relate to point, line, and area features specifically. Well-designed maps follow the label placement rules and use them to resolve conflicts between the labels, as labels should never be plotted over each other.

legend: The map element that allows the map user to translate graphic map symbols into ideas, usually by the use of text.

line thickness: The thickness, in millimeters, inches, or other units, of a line as it appears on a map.

map: A graphic depiction of all or part of a geographic realm where the real-world features have been replaced with symbols in their correct spatial location at a reduced scale.

map design: The set of choices relating to how a map’s elements are laid out, how symbols such as colors are selected, and how the map is produced as a finished tangible product. The process of applying cartographic knowledge and experience to improve the effectiveness of a map.

map title: Text that identifies the coverage and content of a map. This is usually a major map element and can be worded to show the map theme or the map’s content.

map type: One of the set of cartographic methods or representation techniques used by cartographers to make maps of particular types of data. Data, by their attributes and dimensions, usually determine which map types are suitable in a map context.

neat line: A solid bounding line forming the frame for the visually active part of a map.

network map: A map that shows as its theme primarily connections within a network, such as roads, subway lines, pipelines, or airport connections.

orthophoto map: An image map that is an air photo, corrected for topographic and other effects. A specific type of mapping program, at 1:12,000, by the USGS.

page coordinates: The set of coordinate reference values used to place the map elements on the map and within the map’s own geometry rather than the geometry of the ground that the map represents. Often, page coordinates are in inches or millimeters from the lower left corner of a standard-size sheet of paper, such as A4 or 8-1/2 by 11 inches.

permanent map: A map designed for use as a permanent end product in the GIS process.

picture symbol map: A map type that uses a simplified picture or geometric diagram at a point to show a feature type. For example, on a reference map airports could be shown with a small airplane stick diagram, or picnic areas by a picnic table diagram.

place name: A text cartographic element that links a place name to a feature by placing it close to the symbol to which it corresponds, such as a city name as text next to a filled circle.

realistic perspective map: A map of a three-dimensional surface showing a colored or shaded image draped over a topographic surface and viewed in perspective.

reference map: A highly generalized map type designed to show general spatial properties of features. Examples are world maps, road maps, atlas maps, and sketch maps. Sometimes used in navigation, often with a limited set of symbols and few data. A cartographic base reference map is often the base layer or framework in a GIS.

RGB: The system of specifying colors by their red, green, and blue saturations.

saturation: The amount of color applied per unit area. Perceptually, saturated colors appear rich or solid, whereas low-saturation colors look washed out or pastel-like.

scale: The part of the map display that shows the scale of the map figure as either an expression of values (the representative fraction as a number) or as a graphic, usually a line on the map labeled with an equivalent and whole-number length on the ground, such as 1 kilometer or 1 mile.

simulated hill-shaded map: A map in which an apparent shading effect of raised topography is produced by computer (or manually) so that the land surface appears differentially illuminated, as it would in low sun angles naturally.

simultaneous contrast: The tendency for colors at the opposite ends of the primary scale to perceptually "jump" when placed together; for example, red and green.

stepped statistical surface: A map type in which the outlines of areas are "raised" to a height proportional to a numerical value and viewed in apparent perspective. The areas then appear as columns, with a column height proportional to value.

symbol: An abstract graphic representation of a geographic feature for representation on a map. For example, the feature could be a canal, the symbol a blue line of a given thickness.

symbolization: The full set of methods used to convert cartographic information into a visual representation.

temporary map: A map designed for use as an intermediate product in the GIS process and not usually subjected to the normal map design sequence.

topographic map: A map type showing a limited set of features but including at the minimum information about elevations or landforms. Examples: contour maps. Topographic maps are common for navigation and for use as reference maps.

visual center: A location on a rectangular map, about 5% of the height above the geometric center, to which the eye is drawn perceptually.

visual hierarchy: The perceptual organization of cartographic elements such that they appear visually to lie in a set of layers of increasing importance as they approach the viewer.

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