Cartographic Sources

graphic, photographic, digital, and textual data used for the compilation of geographic maps. A distinction is made among astronomical and geodetic sources, including the results of astronomical, triangulation, polygono-metric, and leveling work to establish planimetric and altitudinal geodetic positions (represented primarily in digital form); photographic and surveying sources, including various kinds of surveying materials, such as aerial photographs, photographs produced by ground-based photogrammetric surveying, photographs taken from artificial earth satellites and spacecraft, photomaps, materials produced by topographical surveying methods, and various kinds of maps; and textual and tabular sources, including the results of geographic, economic-statistical, and other kinds of research and generalizations from it.

The recording of the content of cartographic sources in code (usually digital) on punched cards, punched tape, and similar carriers is becoming increasingly common; thus, the required information can be processed, stored, and retrieved by computers. Microfilm and microfiche are also coming into wide use.

Many countries have already begun to establish “banks” of geodetic, topographic, cartographic, and topical cartographic data. The banks are expected to replace most traditional cartographic sources by accumulating information in a form that makes possible the automatic processing, storage, and retrieval of particular data, as well as various combinations of data. The banks are an element in the overall system for the automation of cartographic processes.

In the compilation of a particular map the cartographic sources are tentatively divided into the following categories according to importance: (1) primary sources, from which the basic content of the map is taken; (2) supplementary sources, which aid in the precise determination of individual elements; and (3) auxiliary sources, which are used for general orientation and familiarization with the territory being mapped and with the types of maps and atlases that are similar to the ones being drafted or drawn.

Various criteria are used to evaluate cartographic sources. For example, when evaluating the quality of astronomical and geodetic sources, attention is devoted to their precision and the correspondence between the initial data and the system of coordinates being used in the map being drawn; when evaluating the suitability of aerial photographs, their stereo photogrammetric and photographic qualities and up-to-dateness are considered. The main criteria for the evaluation of general geographic maps are their scale, purpose, authorship, geometric precision, up-to-dateness, and completeness of content and quality of cartographic generalization, as well as the technical and economic feasibility of using the source. Another important criterion in evaluating general geographic and many topical maps—in many cases the decisive criterion—is their ideological and political orientation. The study and analysis of textual and tabular sources belong to special divisions of cartography (population, economic, historical, and soil cartography).