The actual size of USGS topographic map sheets varies depending upon geographic location and map scale. A typical map sheet from the popular topographic map series measures about 20 inches by 28 inches.
Although the USGS produces and distributes other kinds of published maps, this set of online map lists provides information only about USGS published topographic maps (and a very limited number of related maps). This online map-list site presents the same information originally published in the State Map Lists, which are distributed in paper form by the USGS Earth Science Information Centers. Please note that the data available for the State Topographic map list is current through March 2002.
1:24,000-scale maps are relatively detailed, generally covering an area a few miles wide by a few miles high. Maps at 1:250,000 scale are less detailed but cover the same area as 128 7.5-minute maps. A 1:2,000,000-scale map typically covers most of two or more States.
The online map lists provide two dates for most maps: the "currentness year" date and the "version year" date. Usually these dates differ by just a few years but in some cases the difference may be much greater.
The "version year" is the latest date printed under the map name on the lower right-hand corner of a map sheet. Since the number of dates and the format of dates shown on the lower right-hand corner vary from map to map, the date we have selected as the version year will differ from map to map; on some maps it will be a photoinspection date printed in red ink, on others it will be a large date printed in black or brown ink, and on still others it will be yet another kind of date. In all cases, though, it will be the most recent of the dates printed under the map name in the lower right-hand corner.
The version year is usually the same as the year when a map was printed.
The "currentness year" indicates when the information shown on the map was last collected or verified. For example, if the information shown on a map was collected through actual field surveys in 1968 but the map compiled from this information was not published until 1970, the currentness year for this map would be 1968; in this case the version year would probably be 1970. To consider another example, if a map was completed and published in 1974 and was compared with aerial photographs taken in 1995 and was found to be still accurate, the currentness year would be 1995 even though the version year would still be 1974.
In these online map lists, a footnote is used to identify currentness-year dates reflecting photo inspections of maps. These photo-inspected maps have not been modified and the printed editions (though marked with earlier version years in many cases) are still current.
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