Selection: The process of deciding what type and how much information to display on a map Map reading: The process of looking at the map to determine what is represented and how the cartographer represented it For a cartographer, the first step in compiling information about the world becomes something that can be represented on a map. Called selection – the process of deciding what type and how much information to present a card. The cartographer`s selection of features depends on the theme and purpose of the map. Once selected, the features are then generalized to a simplified form adapted to the scale of the map (see Scale and generalization for a set of generalization operators). Selected and generalized data can be manipulated by classification, the process of grouping or organizing characteristics into categories (for qualitative data) or classes (for quantitative data) (see Statistical Mapping). Reading maps is a creative and sometimes difficult task because much of what exists in the environment is not displayed on the map (see scale and generalization), and the features on the map may not occur in reality, but are interpretations of environmental features. Although the cartographer tries to translate reality into as clear a picture as possible of the environment on the map, it is up to the map reader to transform this image into a useful mental image of the environment. As a result, different users may derive different understandings from the same map (MacEachren, 1995). The first reading of the map must reveal the geographical area, the theme and the form of representation of the features or phenomena presented. Map margins are additional graphics and text that appear inside or outside the main map area and help explain or support the map (Figure 2). The map legend is used to confirm the meaning of familiar symbols and provide the logic behind unknown symbols. In addition, this information is sometimes found in explanatory labels on the map itself or in blocks of text (Brewer, 2015).
By definition, map reading and interpretation is the ability to understand the symbols and signs of the map and to derive important information such as settlement distribution and vegetation type. Features of interest must be displayed at the right scale for many mapping purposes (Robinson et al., 1995). Large-scale maps are used to map in detail a small area of soil with little generalization of features (see scale and generalization). When accurate measurements of distance, direction and area are required, only large-scale maps are sufficient. The distortion on a map at a scale of 1:250,000 or more is relatively negligible, so these large-scale maps can be thought of as geometrically accurate representations of the small expanse of land they cover. The crater lake map in Figure 3 has a scale of 1:100,000 and supports reliable reading for purposes such as navigation and path search, geocaching, orienteering, and other activities requiring precise position, distance, and bearing. A correct reading of the image map is supported by an understanding of the many factors that can affect the appearance of remote sensing images, including sensor viewing angle, spectral sensitivity, technical quality, spatial resolution and atmospheric conditions. In addition, card readers may need to understand how black-and-white, true-color, and color infrared images are interpreted, or how to identify variations in the appearance of features and patterns in images captured in the visible, near-infrared, thermal infrared, and microwave (radar) regions of the electromagnetic spectrum. Map maps are valuable tools to help readers better understand their surroundings, develop better mind maps, and ultimately make better decisions. The map allows the reader to visualize the environment as if it were less complicated. Such a simplified image has advantages, but also carries the risk of unrealistic viewing. Through successful map reading, the map and mental maps merge to match the reader`s spatial thinking to the reality of the environment.