GENERAL:
ARC (Ames Research Center) . . . . . . . B&W, BIR, Color, CIR
BIA (Bureau of Indian Affairs) . . . . . B&W, Color, CIR
BLM (Bureau of Land Management). . . . . B&W, Color, CIR
BOR (Bureau of Reclamation). . . . . . . B&W, Color
EPA (Environmental Protection Agency). . B&W, BIR, Color, CIR
JSC (Lyndon B. Johnson Space Center) . . B&W, BIR, Color, CIR
NPS (National Park Service). . . . . . . B&W, Color, CIR
U.S. Air Force . . . . . . . . . . . . . B&W, Color, CIR
U.S. Army. . . . . . . . . . . . . . . . B&W
U.S. Navy. . . . . . . . . . . . . . . . B&W, BIR, Color, CIR
USGS (U.S. Geological Survey). . . . . . B&W, BIR, Color, CIR
NAPP/NHAP:
USGS . . . . . . . . . . . . . . . . . . B&W, CIR
Black-and-white panchromatic (B/W) film primarily consists of a black-and-white negative material with a sensitivity range comparable to that of the human eye. It has good contrast and resolution with low graininess and a wide exposure range.
Black-and-white infrared (BIR) film, with some exceptions, is sensitive to the spectral region encompassing 0.4 micrometers to 0.9 micrometers. It is sometimes referred to as near-infrared film because it utilizes only a narrow portion of the total infrared spectrum (0.7 micrometers to 0.9 micrometers).
Natural color (also referred to as conventional or normal color) film
contains
three emulsion layers which are sensitive to blue, green, and red (the
three
primary colors of the visible spectrum). This film replicates colors as
seen by the human eye. Color film is a valuable image interpretation tool
because the human eye can discern a greater variety of color tones than
gray tones.
What do the different colors in a CIR photograph
represent?
Color infrared photography, often called false color photography because
it renders the scene in other than the normal colors seen by the human
eye, is widely used for interpretation of natural resources. Atmospheric
haze does not interfere with the acquisition of the image, therefore is
well suited to aerial photography. Because the film is high speed and
subject to degrees of degradation in handling before exposure, the
aerial photographs can vary in overall tone. This variability complicates
the interpretation of color tones between photographs. However, some
general guidelines can be given to aid the inexperienced interpreter.
The red tone of color infrared aerial photographs is almost always associated with live vegetation. Very intense reds indicate vegetation which is growing vigorously and is quite dense. An irrigated alfalfa field would be an example of such vegetation. An evergreen forest, which may be quite dense vegetatively, will not appear as a similar bright red because its level of growth activity is less, compared to irrigated alfalfa. Knowledge of the vigor and density of vegetation is important to the interpretation of the red colors on color infrared aerial photography.
As the vigor and density of vegetation decreases, the tones may change to light reds and pinks. If plant density becomes low enough the faint reds may be overcome by the tones of the soils on which the plants are growing. The ground areas in this case will appear in shades of white, blue, or green depending on the kind of soil and its moisture content. As plant vigor decreases, the vegetation will show as lighter shades of red and pink, various shades of greens, and possible tans. Dead vegetation, wheat stubble as an example, will often be shades of greens or tans.
Bare soils will appear as shades of white, blue, or green in most agricultural regions. In general, the more moist the soil the darker the shade of that particular soil color. Composition of the soil will affect the color tones shown on the photographs. Dry sand will appear white and, with more moisture, may be very light gray or possibly light tan. Clayey soils will generally be darker in color than sands and tend toward tans and bluegreens. Again, wetter clays will be darker shades of the same tones. Soils high in organic matter, like silts and loams will be even darker in color, and usually in shades of blues and greens. Wet organic soils can be very dark blue or green in the aerial photographs.
Man-made features will show in the tones that relate to the materials they are made of. Asphalt roads, for example, will be dark blue or black, gravel or dirt roads will show as lighter colors, depending on the soil materials involved in their composition, and concrete roads will appear light in tone, assuming clean concrete. The buildings and streets of towns can be considered in a similar manner, their color dependent on the material they are made of.
Water will appear as shades of blue, varying from nearly black to very pale blue. Clear, clean water will appear nearly black. As the amount of sediment increases, the color becomes increasingly lighter blue. Very shallow water will often appear as the material present in the bottom of the stream. For example, a very shallow stream with a sandy bottom will appear white due to the high level of reflection of the sand.
Degraded film will result in photographs which have an overall blue or
green cast. When that occurs, the interpretation must consider what that
overall cast will do to a "normal" rendition of the scene.
Will I be able to see my house in the photograph?
The NAPP photography provides the most detail. You would probably be able
to identify your neighborhood. There is no guarantee that your home would be
distinguishable. Custom products are available upon request for
non-standard enlargements and exact-scale reproductions.
Do I get more detail with a larger photograph?
No. An enlargement only appears to show more detail than a 9-by-9
inch photograph. Photographic resolution deteriorates with each
enlargement factor.
Why are most of the photographs acquired looking
straight down from the aircraft?
The majority of USGS aircraft photography is used for cartographic
purposes. Image distortion is minimized when photographs are acquired
looking straight down or vertically.
What is meant by the scale of the photograph?
Scale refers to the relationship of distance on photographs or maps to the
actual ground distance. It is a ratio that could represent any unit of
measurement. For example, a scale of 1:40,000 means 1 inch on the photograph
equals 40,000 inches on the ground, or 1 centimeter equals 40,000
centimeters on the ground.
What is meant by resolution?
Resolution refers to the ability to distinguish the smallest visible objects
on a photograph. Resolution is a result of the combination of film type
and the camera lens system.
What is meant by flight line?
A flight line is a path on a map or chart to represent the track
over which an aircraft has been flown or is to fly.
What is meant by focal length?
Focal length is the distance measured from camera lens to film.
Knowledge of the focal length used, along with the altitude of the
photographic aircraft, makes it possible to determine the scale of
the aerial photograph (assuming land uniformity). For example, with
a camera focal length of six inches, a flight altitude of 6,500 feet
above mean sea level, and an average ground elevation of 1,500 feet,
the representative fraction would be computed as follows:
The National High Altitude Photography (NHAP) program was initiated in 1980 and coordinated by the U.S. Geological Survey (USGS) to acquire aerial photography of the 48 conterminous United States every 5 years. This interagency program was designed to eliminate duplicate efforts in various Government programs and to maximize the use of Government funds to build a uniform archive for multiple purposes. In 1987, the program name was changed to the National Aerial Photography Program (NAPP) in recognition of modifications in the user requirements and flight specifications.
The NAPP photography are acquired at 20,000 feet above mean terrain with a 6 inch focal length lens. The flight lines are quarter quad-centered on the 1:24,000-scale USGS maps. NAPP photographs have an approximate scale of 1:40,000, and are acquired on B/W or CIR film, depending on state or federal requirements.
The NHAP photography were acquired at 40,000 feet above mean terrain and
flight lines were centered on the 1:24,000-scale USGS map series. Two
different camera systems were used; a 6 inch focal length lens was used to
acquire B/W film at an approximate scale of 1:80,000 and an
8.25 inch lens was used to acquire CIR film at an approximate
scale of 1:58,000.
When was NAPP/NHAP photography acquired?
The NHAP photography was acquired by the USGS from 1980 to 1987. The
acquisition of NAPP photography began in 1987 and continues.
First
Cycle (1987 - 1991)
Second Cycle (1992 - 1996)
Seven-Year Acquisition Plan (1997 - 2003)
How much area does an aerial photograph cover?
Each NAPP frame covers a 5-by-5 mile area at 1:40,000
scale.
Each NHAP CIR frame covers an 8-by-8
mile area at 1:58,000 scale.
Each NHAP B/W frame covers an 11-by-11 mile area at
1:80,000 scale.
