Index map of high-altitude photography

                           UNITED STATES
                    DEPARTMENT OF THE INTERIOR
                         GEOLOGICAL SURVEY
                     Water Resources Division
                        Washington 25, D.C.

In reply refer to:                          June 3, 1955
                                            Code No. 4051 0001


To:       District Supervisors and Staff Scientists
            of Ground Water Branch

From:     Chief, Ground Water Branch, Washington, D.C.

Subject:  Index map of high-altitude photography

Enclosed is a copy of the index map for the United States, showing
the availability of high-altitude photography and related
compilation materials.  The photography is flown at altitudes
between 20,000 and 32,500 feet.  The resulting scale of the
photographs is from 1:40,000 to 1:65,000.

The material furnished by the Army Map Service is received for the
Geological Survey by either the Special Maps Branch (SMB) or the
Map Information Office (MIO).  The high-altitude material received
is (1) the film negatives, (2) the photo indices showing location
of each exposure, (3) the dia-positives (the glass plates on which
the photography is printed for use in the Multiplex, Kelah, or
other stereo plotters), (4) stereo manuscripts (the maps prepared
form the diapositives) at scale of 1:20,000 to 1:62,500, with a
200-foot contour interval.*  These stereo manuscripts are
constructed on the universal transverse mercator grid system and
do not show geographic quadrangle maps.

This high-altitude material makes it relatively inexpensive for
the Special Maps Branch to supply a base map for any area for
which the high-altitude photography is available.  These base maps
are compiled by photographing the original stereo manuscripts at
the desired scale and mosaicking the resulting negatives to a UTM
grid upon which a regular polyconic projection has been drawn.
The joins between pieces of manuscript are checked and verified.
From the mosaicked negatives, prints can be made in blue, black,
or brown, on either paper, stable plastics, or metal-backed paper.

Paper prints of the high-altitude photographs also may be
purchased from the Topographic Division at their standard price of
approximately .35 per print (lower price on large orders).

In order to show the current material available, this index map
will be reprinted at intervals (about every month or two).  The
number of copies of these future maps will be limited.  Therefore,
if you wish to receive the subsequent copies of this index, please
make written request to this office.

                                  (s) A. N. Sayre

Attachment (Map)

Distribution:  A, B, GS, FGO
     Because of the limited number of maps available, a copy is
not being sent to those district offices in states where
photography is neither accomplished nor planned.  Copies will be
furnished when photography is planned for those areas.

*  Information just received indicates that some manuscripts have
100 foot contours.