Summary of Key Concepts
The word "map" sometimes has a very broad meaning. We talk of "concept maps," mental maps," and "mapping out my day." In the Mapping guide, however, we focus mainly on maps that are used to communicate about physical space. This narrower type of map is called a spatial or geographical map. Such a map might show friends how to get to one's home, or how the rooms are laid out. These maps reveal different ways to get to a destination, the towns a road passes through, and the distances between the towns. Other spatial maps tell of topography, the weather across the country, or the incidence of a disease, all as functions of location. The focus of Mapping is upon maps as tools of communication. The basic idea is that maps represent places and the locations of things.
Spatial maps are meant to communicate what is in a space, and where each thing is. The map-reader expects a correspondence between what is shown on the map, and what is seen in that part of the real world represented by the map. If the neighborhood map shows a school and two candy shops, we expect to find a school and two candy shops when we visit the neighborhood. There should also be a correspondence between the relative positions of things shown in the map and the positions of those things in the real world. If the map shows one candy store across from the school and the other a block to the east, then that is where we should find them on the actual street.
Correspondence in mapping is somewhat of a one-way street. We expect the things shown in a map to be present in the real world. However, we don't expect everything in the real world to be present in the map. Potholes are an unpleasant part of a driver's trip, but we don't expect them to be shown on a map - unless of course we are members of the road crew sent to repair the potholes. Maps only show the things that the map-maker wants to emphasize; i.e., that are part of the information that the designer of the map wants to communicate.
In order to depict real-world things the map-maker uses symbols. The symbols may range from a drawing of the thing, to an icon, to something as abstract as a geometrical form. In the initial maps of their rooms, children usually draw pictures of the bed, dresser, desk, television, and so forth. Later they develop more abstract ways to represent these things. As the symbol system becomes more abstract, the need for a legend or key becomes more apparent. The key connects each symbol with its meaning.
Maps are drawn from one or more points of view or perspectives. In their earliest maps, children may use multiple points of view. In children's first maps of their bedrooms the bed is frequently drawn from the top, or bird's eye view, while the dresser and walls are drawn from a side view. As they gain experience, children become more consistent in their use of perspective.
When using a map to find the way to a destination, the map must be oriented to the space it represents. There are two main ways to orient a map to a space. If the direction of North is known and the map shows North by an arrow or compass rose, then turn the map so the arrow indicating North points in the northward direction in real space. To use the second method of orientation, identify where you are on the map. Then align the map so that the direction from your location to a landmark on the map is the same as the direction from you to the same landmark in the real world. A landmark could be anything shown on the map, and also observable from where you are.
Most published maps are drawn to a scale. This means that a particular distance on a map represents a specified distance in the world; for example, one inch stands for one mile. Thus if it is one mile from 100th Street to 120th Street, then the map is drawn so that the map distance from 100th Street to 120th Street is one inch. The scale expresses the fixed ratio or proportion between map distance and real distance. By appropriate choice of scale, a map-maker can fit a whole country, a state, a city, a building, a classroom, or a desk top on an 8 ½" x 11" piece of paper. If the scale is reasonable, the map can be made to fill most of the available paper.
The set of lines on graph paper is called a grid. A grid is useful in making a map to scale. Initial classroom maps may use a scale in which one grid square represents one floor tile. The grid can also provide a way of finding specific locations on a map. Letters and numbers can identify the horizontal and vertical rows and columns, respectively. Then, each square on the map is assigned a letter and a number, based on the row and column that intersect there; e.g., the intersection of row G and column 8 would be called G8. In math, this method of identifying a location in space is called a coordinate system.
