For instance, in geometry, we use x (horizontal) and y (vertical) coordinates to define points on a two-dimensional plane. Coordinate systems are frameworks that are used to define unique positions. Just as all maps have a map scale, all maps have locations, too. Therefore, understanding map scale and its impact on how the earth and its features are represented is critical for map-making and GIS. Though some say that online maps and GIS are “scaleless” because we can zoom in and out at will, it is more accurate to say that GIS and related mapping technology are multiscale. Determining the thresholds for small- or large-scale maps is a judgment call.Īll maps possess a scale, whether it is formally expressed or not. Furthermore, while the large-scale map shows more detail and less area, the small-scale map shows more but less detail. ![]() For instance, a map with an RF of 1:1,000 is considered a large-scale map when compared to a map with an RF of 1:1,000,000 (i.e., 1:1,000 > 1:1,000,000). Map scales can also be described as “small” or “large.” Such descriptions are usually made about representative fractions and the amount of detail represented on a map. Such units could be inches, centimeters, or even pencil lengths it does not matter. One unit on the map represents 10,000 units on the ground. For example, consider a map with an RF of 1:10,000. In other words, any unit of measure can be used to interpret the map scale. One of the benefits of using a representative fraction to describe scale is unit neutral. The numerator, always set to one (i.e., 1), denotes map distance, and the denominator denotes ground or “real-world” distance. The representative fraction (RF) describes scale as a simple ratio. “ Travel Atlas” is licensed under the Creative Commons Attribution 1.0 Universal Public Domain. Scale bars are usually used on reference maps and allow map users to approximate distances between locations and features on a map and get an overall idea of the map’s scale. Map scale can also be portrayed graphically with a scale bar. For example, it is common to see “one inch represents one kilometer” or something similar written on a map to give map users an idea of its scale. Map scale can be represented by text, a graphic, or some combination of the two. Map scale refers to the factor of reduction of the world so it fits on a map. Nonetheless, all maps reduce or shrink the world and its geographic features of interest by some factor. What exactly is meant by “manageable” is open to discussion and depends on the purpose and needs of the map at hand. One of the most significant challenges behind mapping the world and its resident features, patterns, and processes is reducing it to a manageable size. Moreover, map projections are concerned with moving from the three-dimensional world to the two dimensions of a flat map or display. Coordinate systems help us define the positions of features on the earth’s surface. Map scale is concerned with reducing geographical features of interest to manageable proportions. The essential cartographic considerations are map scale, coordinate systems, and map projections. Several other formal and informal mapping conventions and characteristics can be identified, many of which are taken for granted. Though this may not always be the case, many map users expect the north to be oriented or coincide with the top edge of a map or viewing device like a computer monitor. For example, one of the most recognized mapping conventions is that “north is up” on most maps. Mapping or cartographic conventions refer to the accepted rules, norms, and practices behind making maps. Mapping conventions facilitate the delivery of information in such a manner by recognizing and managing the expectations of map users. For a map to be of value, it must convey information effectively and efficiently. The central purpose is to provide relevant and valuable information to the map user. Understanding and meeting the expectations of map viewers is a challenging but necessary task because such expectations provide a starting point for creating any map. However, it is essential to note that such expectations also change with increased exposure to maps. ![]() Such expectations are formed and learned from previous experience by working with maps. 2.3 Datums, Coordinate Systems, and Map ProjectionsĪll map users and viewers have certain expectations about what is contained on a map.
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