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Inset maps are smaller maps that are included on the same page as the main map. They can show additional information related to the main map. Four types of inset maps are common: [6] A Locator map is of a significantly smaller scale than the main map, and is used to show the location of the main map within a larger context. They are especially ...
Tissot's indicatrices illustrate linear, angular, and areal distortions of maps: A map distorts distances (linear distortion) wherever the quotient between the lengths of an infinitesimally short line as projected onto the projection surface, and as it originally is on the Earth model, deviates from 1. The quotient is called the scale factor.
A conformal map has an isotropic scale factor. Conversely isotropic scale factors across the map imply a conformal projection. Isotropy of scale implies that small elements are stretched equally in all directions, that is the shape of a small element is preserved. This is the property of orthomorphism (from Greek 'right shape'). The ...
Inset maps may serve several purposes, such as showing the context of the main map in a larger area, showing more detail for a subset of the main map, showing a separated but related area, or showing related themes for the same region. A bar scale or other indication of scale translates between map measurements and real distances.
One problem is the variation of scale with latitude, and another is that straight lines on the map (rhumb lines), other than the meridians or the equator, do not correspond to great circles. The distinction between rhumb (sailing) distance and great circle (true) distance was clearly understood by Mercator.
During the first half of the 20th century, cartographers began to think seriously about how the features they drew depended on scale. Eduard Imhof, one of the most accomplished academic and professional cartographers at the time, published a study of city plans on maps at a variety of scales in 1937, itemizing several forms of generalization that occurred, including those later termed ...
In each zone the scale factor of the central meridian reduces the diameter of the transverse cylinder to produce a secant projection with two standard lines, or lines of true scale, about 180 km on each side of, and about parallel to, the central meridian (Arc cos 0.9996 = 1.62° at the Equator). The scale is less than 1 inside the standard ...
Generalization: All maps must be drawn at a smaller scale than reality, requiring that the information included on a map be a very small sample of the wealth of information about a place. Generalization is the process of adjusting the level of detail in geographic information to be appropriate for the scale and purpose of a map, through ...