Various types of socio-economic data are the basis for mapping. Qualitative data are represented by point, line and area symbols. Area on a small scale map by points, roads, railways and coastline by lines, and political units, forests etc., by area symbols are shown on the maps. These are not always drawn to scale. The qualitative maps thus prepared are general reference, pictorial and thematic maps. Certain techniques used to depict the terrain and climatic data are also applicable for socio-economic data. Mono dot, multiple dots, dots and circles, spheres, graphs, (simple, semilog) flow charts, bars, ray diagram, isochrones, pyramidal graph, and block piles are used. The cartographer faces problems of representation in the case of discrete and continuous geographical variables. The distribution of various phenomena is done because of the possibilities of converting continuous data into discrete and vice versa. Choropleth, Dasymetric and Isarithmic maps are likewise prepared. Pictorial maps are very good illustrative materials for class room purposes.
Thematic Mapping
General purpose maps are relevant to all specialists as well as the common man but thematic maps like the soil map are useful for a specific purpose. By and large thematic mapping is essentially a function of small scale cartography. Simple thematic map are those of a single feature and complex thematic maps are the association of two or more phenomena. Cartography being the study of spatial distribution, combinations and interdependencies between nature and society and of their changes through time, it can have as many branches as there are disciplines. Recently, space cartography has emerged with emphasis on the lunar surface. Thematic cartography caters to the needs of a variety of specialists. It becomes a possible tools of scientific research, in any discipline that is concerned with measurement and spatial processes. Its development depends on the cooperation between the cartographer and the subject specialists.
Atlas Mapping
Atlas cartography presents unique problems. An Atlas is like a book and each map is a chapter or a part of a chapter. The specialized atlases contain thematic maps of both qualitative and quantitative natures. Depending upon the nature and amount of data to be represented, atlas maps are drawn on a variety of scales. Some maps show physical while others cultural data. Some give only generalized information. The design contents and the size of the maps vary with the shape of the area and the amount of data to be represented.
Map Reproduction
Most maps are reproduced for multiple copies. Reproduction processes are duplicating and printing. Widely used duplicating processes are stencil duplication or mimeographing, direct contact positive and direct contact negative. These processes give only a limited number of copies. The printing processes that are used are letter press or relief press, photogravure or intaglio process and lithography or planographic process. A few recent developments such as 'scribing' appear to be a short cut between the original drawing and the photographic negative. The extreme dimensional stability of the base and the relatively greater accuracy by scribing, combine to make maps clear and concise. It is a more rapid process than the conventional drafting.
Cataloguing and Storing
Maps are more diversified in nature than books. Cataloguing and classification are therefore different. Catalogues incorporate the details of a person or an organization responsible for it, cartographer, publisher, copyright holder, title, scale, edition, size, place and date of publication. In cataloguing a modern map, the order of importance should be
1. place delineated
2. subject (purpose)
3. date
4. author
It is desirable to follow a rational system of classification. It is based on the size and use of maps. The maps are classified into atlases, wall maps, topographical, weather, aeronautical and navigational charts. The atlases are divided into general, regional and thematic. Classification is only a part of the problem of map collection. Proper care is necessary from the very beginning. Map mounting is a very simple operation. Dry map mounting is used in the U.S. Filing cabinet, and racks are necessary to store topographical maps and wall maps. Since the finished maps are the result of the mutual interests of map makers and map users, the type and quality of the map has to be decided by their cooperation. The cartographer should try to meet the needs of the map user. It is the job of the salesman to create awareness and availability of the required maps. Each new awareness creates demand and each new demand creates new cartographic products. Thus the cartographer serves the people.
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