Asterisks are placed between the sheet number and the edition number when necessary to ensure there are at least 11 units in the stock number. Normally found in the right margin, this graph indicates the conversion of different units of measure used on the map. The purpose of a map is to permit one to visualize an area of the earth's surface with pertinent features properly positioned. The map's legend contains the symbols most commonly used in a particular series or on that specific topographic map sheet. Therefore, the legend should be referred to each time a new map is used.
Every effort is made to design standard symbols that resemble the features they represent.
If this is not possible, symbols are selected that logically imply the features they portray. Ideally, all the features within an area would appear on a map in their true proportion, position, and shape. This, however, is not practical because many of the features would be unimportant and others would be unrecognizable because of their reduction in size. These symbols resemble, as closely as possible, the actual features themselves as viewed from above. They are positioned in such a manner that the center of the symbol remains in its true location.