-------- Original Message --------
Subject:        RE: MAPS-L: New York State Topos?
Date:   Wed, 22 Mar 2006 11:56:22 -0500
From:   Zellmer, Linda R <[log in to unmask]>
To:     Maps, Air Photo & Geospatial Systems Forum <[log in to unmask]>


Hello,

There is information on USGS Topographic map dates at
http://erg.usgs.gov/maplists/howtoselectmaps.html, which gives the
following information on Topographic map dates. I hope this helps. Linda
Zellmer


Currentness Year and Version Year
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.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Linda Zellmer
Head, Geology Library
Geology Building, Room 601
1001 E. 10th Street
Bloomington, Indiana 47405-1405
Phone: (812) 855-2275 Fax: (812) 855-6614
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