General geographic maps are used as sources for all thematic maps. They serve as the basis for drawing thematic content. Topographic, survey-topographic, and survey maps are reliable and trustworthy sources, which are created according to state instructions, in a standard system of symbols with certain, strictly fixed accuracy requirements.
The entire territory of Russia is covered by topographic maps at a scale of 1:25,000 or less. Some territories have maps on a larger scale. Other countries, comparatively small in area, have maps on a much larger scale, for example, the entire territory of Great Britain is mapped at a scale of 1:2,500. The whole planet is covered by international maps at scales of 1:1,000,000 (about 1,000 sheets) and 1:2,500,000 (262 sheets).
The importance of general geographic maps is not limited to their use for linking thematic content. ”They provide geographic reliability of mapping, playing the role of a framework, in relation to which the mapping and subsequent linking of thematic content of the map being made, as well as the mutual coordination of maps of different topics.
Thematic cartographic materials – the main source for thematic maps. They include:
- results of field thematic surveys (large-scale plans, charts, sketches. route and stationary surveys, etc.)
- thematic maps of various scales and purposes
- special materials (land use schemes, forest management plans, etc.).
Large scale thematic maps always serve as sources for small scale maps, but it is especially important that maps of one subject are often used for drawing maps of related subjects. For example, vegetation and geomorphological maps are used for soil mapping, geological and tectonic maps for geomorphological maps, settlement maps are used for transport maps, etc. And for synthetic zoning and territory assessment maps a series of maps of different topics is often used as a source. Modern abundance of thematic materials puts the task of optimizing their selection in the creation of any map, and this requires the cartographer to have deep geographical knowledge.
A special type of sources are cadastre maps and plans. They document the location, qualitative and quantitative characteristics of phenomena and natural resources, give their economic or socio-economic evaluation, contain recommendations for rational use and protection of natural resources. These are maps of cadastre of land, urban, minerals, forest, water, fishery, etc.