Mapmakers, also known as cartographers, create maps with particular purposes to ensure accuracy and clarity. Purposes include the representation of natural landforms for topographic maps, political boundaries and toponyms for political maps, and roadways and routes for road maps. Mapmakers also create specific maps to represent phenomenon such as population or climate. The purpose of the map dictates which elements of a region the mapmaker will graphically represent on the finished product. This, in turn, determines which specific information the mapmaker requires to complete the map.
A mapmaker usually represents a map on a flat surface. Even globes, which more closely align with the shape of the Earth, utilize certain conventions that do not precisely present scaled information. The projection is the way in which mapmakers modify or flatten cartographic information to ease the creation of the map. Mapmakers use different methods of projection depending on the purpose of the map. Dozens of types of projections exist, each possessed of different qualities. Mapmakers often use a flat, rectangular projection for road maps for the ease of the scaling of miles. Several commonly used projections include the Mercator projection, the Mill Cylindrical projection and the Gall-Peters projection. An orthographic projection represents a simulated sphere on a flat surface. This presents the most accurate information regarding the shapes and sizes of details of the planet's surface, but does not lend itself to scaled drawing, due to the visual distortion resulting from the perspective. An orthographic projection also limits the amount of the Earth's surface that displays.
Mapmakers use several different tools to gather information for their maps. Traditional tools include magnetic compasses, surveying instruments, telescopes and binoculars. By using ground level observations from these instruments, mapmakers gather the necessary data to plot points on the map. At the time of publication, mapmakers use global positioning and satellite photographer to gain information from above the earth. Since the development of aircraft, they have also used planes and helicopters to photograph landforms from the air.
While it is possible to plot accurate maps from aerial and satellite photographs, mapmakers also use methods such as triangulation and plane-table mapping to establish their maps. Mapmakers primarily use triangulation to determine a precise location of a person, area or object in relation to other known features. The mapmaker determines the distance and direction of at least three objects from a single location and draws lines through the objects to find an intersection. This intersection marks a precise single location. For plane-table drawings, the mapmaker starts from a single known location and uses observation to plot nearby points. At the time of publication, mapmakers also make use of Geographic Information Systems, or GIS, which is a network of computers, organizations and individuals working together to gather, analyze and display geographic information. This allows the mapmaker to synthesize information from a broad range of sources and allows the mapmaker to handle each aspect individually. This contrasts with older mapmaking traditions, wherein the map itself was both the display and the data.
