A comment by Diane E. Lane about
Regarding Tom Berg's item J.: The USGS, specifically the National Mapping Division, has defined accuracy standards for such lines as contacts. A contact is to be shown as a solid line if it is located within a distance represented by 1 mm at the scale of the map. If not, it is dashed and defined as approximately located or dashed and defined as inferred (no data to establish contact but contact must be present), indefinite (insufficient data to establish contact with certainty), or gradational (continuous change from one lithology or rock type to another, contact arbitrary). Concealed contacts are shown as dotted lines. The same accuracy standard applies to such features as folds and faults. For a scalable database it would seem necessary to state the accuracy explicitly at a given scale. In actual practice, I (as a map editor) don't see many maps where the author has tried to distinguish between approximate and inferred contacts. Even then, exactly what that means to the author is not necessarily stated in the map explanation.
(This page is the only comment that has been posted so far.)Further discussion of accuracy of location of contacts and other features (this page):
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