It is helpful to examine mapping and examples of established soil series in nearby areas that have been recently surveyed. Unpublished soil surveys of scattered farms are another source of information about the area. The value of this information depends on the quality of the legend and consistency of mapping over long periods. Regardless of the quality of the legend, the scattered farm mapping should not be made a part of the modern soil survey without careful field checking. A soil survey is a study of the geography of soil.
Maps detail geographic information.
Aerial photographs, topographic maps, and other maps are useful references whether or not they are used as the mapping base. Each kind of map shows features that the others do not. Topographic maps are the best references for appraising relief for most areas. Maps and texts on geology for many areas have been published by the U.S. Geological Survey and by comparable State agencies. The publications are on various subjects, such as bedrock geology, surficial deposits, and water or mineral resources.