Air Photos in the Map Collection
The air photos of Georgia, held by the University of Georgia Libraries,
Map Collection, are from several federal or state agencies. The
majority of the holdings, and most of the online air photos, are
from the U.S. Department of Agriculture or the U.S. Geological Survey.
The Map Collection currently holds aerial photography produced by
(items italicized are currently online in this
database):
U.S. Department of Agriculture
The early photos covering Georgia were originally done for agencies
of the U.S. Department of Agriculture (USDA). In 1933, several farm
programs started requiring accurate measurements of farms. Up to
that point precise measurements of land was done by field surveying,
much as it had been done for hundreds of years. Millions of acres
of agriculture land across the country needed to be measured and
mapped so a quicker and cheaper way was devised. In 1935, USDA began
to use rectified-to-scale aerial photography to measure agricultural
land.
Two USDA agencies are responsible for most of the USDA air photos
held by the Map Collection. One agency has changed names, starting
as Agricultural Adjustment Administration, but was more commonly
known as the Agricultural Stabilization and Conservation Service
(ASCS), and was responsible for many of the crop and conservation
programs. The other agency was the Bureau of Soils, or Soil Conservation
Service (SCS), which was responsible for the soil-mapping program.
The USDA developed a photogrammetric system to measure all the agriculture
land in the United States based on a standardized aerial photography
program. In this program, which was based in part on a similar project
done for the Tennessee Valley Authority (TVA), an air photo survey
was done of each agricultural county in the country at regular intervals.
Each county survey had to meet an established photogrammetric standard
and was done under contact by private companies. Once produced,
the county survey was used by the agencies and county agents to
manage crop programs and to map land.
The standard ASCS air photo survey of an agricultural county produced
a photo set flown to photogrammetric standards. In general terms
the sets have the following characteristics:
- A standard photo scale of 1:20,000 across the entire photo.
- Photos overlap each other and the county boundary so stereoscopic
views of the entire county is provided.
- Flight lines run north and south. Flight lines, photo numbers,
and the coverage area of individual photos are different from
year to year in each county set.
- Each photo has standard information printed at the top of the
north edge of the photo. The standard information on the photo
includes: date, a county identifier, flight line number, and photo
number. Each county in the U.S. was given a two or three letter
code as identification, such as: CDR. With the introduction of
the FIPS code in the 1970's, the letter code was changed to a
five number code, for example: 13001. Thus a code at the top of
a photo of (2-23-40, CDR 2 42) indicates the photo was taken February
23, 1940; the county is Appling County, Georgia; the flight line
is 2; and the photo number is 42.
- A photo mosaic index was made of the county photo set. The photo
mosaics specified for USDA are the assembling of all the photographs
in the set in such a way that they form a continuous photographic
representation of the county and so the flight line and photo
numbers of each photo can be seen. The mosaic appears to be a
photo of the entire county created by layering individual photos
on top of each other so that the top, right corner of each photo
can always be seen.
- Photography was scheduled during the leafless period and during
hours of low shadows. In Georgia, this was in the winter months
and within 2-3 hours of 12pm.
- The photographs had to be shot on a clear day, free of clouds.
To achieve this, it was likely that the photographs were scheduled
on different days which resulted in some sets of photographs spanning
over two years. For example, you may see photos taken during December
of one year in a group with photos taken during January of the
next year.
- Black and White (or Panchromatic) film was the typical format
used for these photographs.
- The USDA photography was shot by county. In a few cases, the
county set covers only the agricultural part of a county (in the
case of Fulton county) or covers two counties.
- The standard set of stereo air photos changed very little over
the years between 1935 and 1985. The major changes that can be
seen in the Map Collection's holdings are:
- A change in the size of a photo image from 6 inches by 9
inches to 9 inches by 9 inches around 1939.
- A change in the standard scale from 1:20,000 to 1:40,000
in the mid-1970's.
- Changes in the contact print types over time.
- In many cases, especially for the early years, the contact prints
in the Map Collection have a higher quality than the prints that
are currently available from the National
Archives. This is due to the collection being primarily second
generation prints taken from original negatives. Unfortunately,
those negatives are no longer in existence and the images in the
National Archives are on microfilm.
The Map Collection acquired USDA photography by requesting, for many
years, the donation of any surplus photography of Georgia from the Department
of Agriculture. The Map Collection also acquired indexes and photography
from other donors. USDA photography is arranged in the Map Room by Georgia
County. Since it was originally done for the federal government it can
be freely used and is without copyright restrictions.
The USDA photos done before 1955 have been transferred to the National
Archives. Photos produced after 1955 by the USDA can currently be
acquired from the Aerial
Photography Field Office of the Farm Service Agency.
U.S. Geological Survey
The USGS began to rely heavily on aerial photographs in topographical
surveying after World War II. Photography was done to strict photogrammetric
standards and was produced in sets, much like that done for USDA,
but based on topographic quadrangles, rather than counties. In the
1970’s The State of Georgia and the USGS entered into a cooperative
program to complete the 1:24,000 scale topographic quadrangle map
series for Georgia. As part of that program a large number of quadrangles
in Georgia were flown, and that photography is held by the Map Collection.
Since the late 1980’s, the USGS has had responsibility for
the production of a standardized set of cloud-free aerial photographs
covering the conterminous U.S. over five-to-seven year cycles. The
program began in 1987 and continues under The National Aerial Photography
Program (NAPP). The Map Collection holds a set of the 1988, 1:40,000
USGS photography for Georgia.
The quadrangle photography produced by the USGS was done under standards
comparable to the USDA photography. In general terms the sets have
the following characteristics:
- Photo scales can vary from 1:19,000 to 1:77,000, but most around
1:20,000 scale.
- Photos overlap each other and the quadrangle boundary so stereoscopic
views of the entire quadrangle are provided.
- Flight lines run north and south. Flight lines, photo numbers,
and the coverage area of individual photos are different from
year to year in each set.
- Each photo usually has standard information printed at the top,
north edge of the photo. The information can vary according to
the mission.
- A photo mosaic index was made of the quadrangle photo set. The
photo mosaics are a layering of the photographs in a set in such
a way that they form a continuous photographic representation
of the quadrangle and so that the flight line and photo numbers
of each photo can be seen.
- The photos were scheduled according to the needs of the particular
USGS mission. In many cases, this was during the winter months
when there was no foliage on the trees and low shadows. Again,
as with the USDA photos, they were photographed within 2-3 hours
of 12pm.
- The photographs had to be shot on a clear day, free of clouds.
To achieve this, it was likely that the photographs were scheduled
on different days which resulted in some sets of photographs spanning
over two years. For example, you may see photos taken during December
of one year in a group with photos taken during January of the
next year.
- Black and White (or Panchromatic) film was the typical format
used for these photographs, but color IR film was also used.
- The USGS photography was completed in sets based on USGS topographic
quadrangles.
The Map Collection acquired a majority of the USGS photographic holdings
by donation from several state agencies. In addition, the Map Collection
acquired indexes and photography from other donors. USGS photography
is arranged in the Map Room by quadrangle name. However, it is listed
by county in the Air
Photo Holdings lists available in the Map Room and online. Since
it was originally done for the federal government it can be freely used
and is without copyright restrictions.
The USGS photos can currently be acquired from several locations.
- The NAPP photography can be acquired from the EROS
Data Center or you can search
their database.
- Terraserver
- To search the USGS database for older federal photography, use the
Earth
Explorer.
Other Air Photo Producers
While the USDA and USGS produced air photos make up the
bulk of the aerial photographs in the Map Collection holdings, there
are several other groups of photography. The groups produced by federal
agencies mainly follow standards that are fairly close to the USGS
and USDA photography. The other groups have a wide range of standards.
These groups will probably not be mounted online and will have to
be researched in the Map Room.
The Georgia mountain and coastal counties have limited coverage because
they were not considered agriculture counties by USDA. The Map Collection
does not have Forest Service photo coverage for Georgia. The collection
does have a set of TVA photography covering parts of North Georgia
from 1975. The collection holds a set of Georgia DOT photography of
coastal Georgia from the 1975. The collection also holds some very
limited sets of photography of several road intersections produced
by the Georgia DOT.
In the 1970’s, NASA flew a series of projects using high-altitude
planes that produced several sets of Color IR for Atlanta and central
Georgia. There is a very limited amount of U.S. Army coverage of dams
and coastal areas in the collection. The collection holds a set of
Athens-Clarke County photography produced by the Planning Commission.
The Map Collection holds a large set that covers the Atlanta metro
region during the 1980’s but since it was privately produced
it will not be put up online and can be used only within the Map Room.
There are several sets of aerial photography that cover small areas
in Georgia that were produced for special research projects.
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