This article comes from ESRI help document
Cartography can be described as the graphic principles supporting the art, science, and techniques used in making maps or charts. It was developed in a time before the computer and geographic information system (GIS) technology. Throughout its development, which continues, many critical principles have been established to advance cartography, such as Jacques Bertin’s visual variables for symbology: size, value, texture, color, orientation, and form. He defined these variables to assist someone in representing one symbol differently from another. Other advancements have been developed through studies of human psychology and visual perception. Traditionally, maps have been created to serve two main functions. The first function has been to store information. Creating a map has been a way to record information for future reference. The second function has been to provide a picture to relay spatial information to a user. The purpose for designing a map is critical to its design. When designing a map, a mapmaker needs to know the answers to some fundamental questions, such as: What is being mapped? Who is the audience? How is this map being presented, on its own or as part of a report? What medium will be used to display this map?
Generally, maps can be in two formats. One is a general reference map such as a United States Geological Survey (USGS) topographic map or a city map. In this form, the map is providing information to convey where things are in relation to each other. The second is a thematic map, where the map is used to convey information about a particular theme or multiple themes, such as land use, population, or health statistics.
Basic mapping principles
There are many types of maps, each with general and possibly specific requirements. While a skilled cartographer is usually required to make maps with specific or special requirements, anyone can make good, general, and informative maps by considering the following simple guidelines. These guidelines have been organized into seven areas that you can use as a checklist for creating or improving your maps:
- Purpose—Typically, a map does not have more than one purpose. Trying to communicate too much in one map—having more than one purpose for the map—tends to blur the message and confuse the map reader. Using two or more maps, each focused on a single message, is always a better strategy.
- Audience—Who will be reading your map? Are you designing a map for a few readers or for a large audience of hundreds or millions of people? It’s better to target your map to the person least prepared to understand your map’s message.
- Size, scale, and media—The physical size of a map relative to the geographic extent shown on the map will dictate the scale of the map and determine how you will represent the actual size and number of features shown on the map. Data is often collected at a particular scale. However, if you’re not displaying the data at that scale, be sure your data fits. For example, roads typically collected for 1:24,000 mapping will be far more detailed than needed for a smaller scale map (such as 1:2,000,000), so be sure to reduce the number of roads drawn on your map. As you can see below, the road data displayed in the map on the right is clearer than the map on the left—sometimes less is better.
- Media also plays an important role, because a map printed on newsprint will not show fine details clearly, whereas one printed on high-quality paper will. In addition, the details on a digital map could vary depending on the viewing program. For example, a static map used on a Web page would be designed to encompass less information than one designed for browsing using a program such as ArcReader.
- Focus—Refers to where the designer wants the map reader to first focus. Typically, cool colors (blues, greens, and light gray) are used for background information, and warm colors (red, yellow, black) are used to capture the reader’s attention.
- Integrity—You may want to cross validate some of your information, such as the names or spelling of some features. If the data was produced by another organization, it is customary to give that organization credit on the map.
- Balance—How does your map look on the page or screen? Are the parts of the map properly aligned? The body of the map should be the dominant element. Try to avoid large open spaces. Be flexible in where you place elements (that is, not all titles need to go at the top). Should some components on the map be contained within a border? In the graphics below, the first example displays a map layout with unnecessary open spaces, whereas the second graphic makes better use of space within the layout.
- Completeness—A map generally should contain some basic elements, such as a title, legend, scale bar, and north arrow; however, there are exceptions. For example, if a graticule exists, it is not necessary to place a north arrow. Basically, place all the information you think your readers need to fully understand the map.
Before publishing your map, it is always a good idea to have someone else look it over, especially for spelling and overall appearance.
- Map body—The primary mapped area. You can display more than one image of your primary mapped area within your document. For example, you may want to portray change by showing several images with differing but related information, such as population maps of various years. Your map may also contain a locator map (a smaller-scale map used to help the reader understand where the main area of interest is located), an inset map (used to give more detailed information of an area within the main map that may not easily be understood), or an index map (often used to show where in a series of maps one map exists). All are used to assist in communicating your information to others. In ArcMap, each of these mapped areas is referred to as a data frame.
- Title—Used to tell the reader what the map represents. This is often placed on a map layout as text.
- Legend—Lists the symbology used within the map and what it represents. This can be created using the Legend wizard in the layout and edited further once created.
- Scale—Provides readers with the information they need to determine distance. A map scale is a ratio where one unit on the map represents some multiple of that value in the real world. It can be numeric (1:10,000), graphic (a scale bar), or verbal (1 inch equals 10,000 inches). Maps are often referred to as large or small scale. This size reference refers to the ratio (or fraction). For example, a 1:100 scale map is larger than a 1:10,000 map, because 1/100 (0.01) is a larger value than 1/10,000 (0.00001). A smaller-scale map displays a larger area but with less detail. The graphic below on the left displays the details you might see in a small-scale map, and the graphic below on the right displays the details you might see in a large-scale map.
- The scale is inserted in the map layout view.
- Projection—A mathematical formula that transforms feature locations from the earth’s curved surface to a map’s flat surface. Projections can cause distortions in distance, area, shape, and direction; all projections have some distortion. Therefore, the projection type is often placed on the map to help readers determine the accuracy of the measurement information they get from the map. Learn more about projections
- Direction—Shown using a north arrow. A map may show true north and magnetic north. This element is inserted in the map layout view.
- Data source—The bibliographic information for the data used to develop the map.
Other map components include (but are not limited to) dates, pictures, graticules or grids, reports, tables, additional text, neatlines, and authorship. View a diagram of map elements
Mapping and GIS
So how are mapping and GIS related? For starters, GIS has its roots in mapping—both involve maps and attributes, and both use geographic data involving map scales, projections, and coordinate systems. There are three basic users for both mapping and GIS—the viewer, the maker, and the designer. Before outlining their roles, it must be stated that these users can overlap—a viewer may be the maker or a maker be the designer—or they can all be the same person.
- Viewer—This person, who can be described as the end user, is generally the reason for the existence of the map or data. The viewer is the person using a Web mapping program to determine the route from his or her home to the museum, the oil company executive who needs to locate potential drilling sites, a person planning a mountain hike, or a newspaper reader who is making the association between a new industrial site and his or her home.
- Designer—The designer can be involved at the beginning, end, and throughout the GIS or mapping product creation process. This person determines what data to use, what tools to use, how to acquire the data, and so on. The designer can be the person who creates the output by defining what questions will be answered and how data is going to be displayed on the map. The map designer could also be the person specifying which symbols to use to represent roads or the project developer who is writing the contract proposal for an environmental assessment using GIS.
- Maker—This is the person working with the data by editing, creating, acquiring, querying, or analyzing it. The maker is the person who is merging the road dataset, digitizing the rivers, editing the parcels, attaching the address locations, buffering the protected lands, analyzing the population projections, importing the elevation models, or identifying the new school locations.
How else are mapping and GIS related? GIS is used for display, analysis, storage, and retrieval. The mapping output is used to display and store information. From this, a person can retrieve information and use that information in analysis. Mapping and GIS are becoming closer to one another through technological advancements. For example, a map is no longer a static product, and visualization is not dependent on a printable medium. Viewers have been given the ability to interact with the display. Basically, the cartographic principles of mapping can be thought of as the rule for output, and GIS can be considered the tool to bring information together.