Aerial Photography

Terminology

By Bob Cozby

| A | B | C | D | E | F | G | H | I | K | L | M | N | O | P | R | S | T | U | V | W |

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A.B.C location method:

A method for indicating locations within a map or Image that was utilized by the USGS in the Series of 100 Topographic Maps

Absorption:

The process in which incident radiant energy is absorbed and converted to other forms of energy

Active System:

This is a type of remote sensor, such as radar or sonar, that sends out some sort of signal to "paint" the target.

Aerosols:

Tiny liquid or solid particles that exist suspended in the atmosphere.

Airphoto interpretation:

A sub-field of remote sensing that deals with the extraction of information from photographs that acquired reflected energy from above the Earth's surface.

Albedo:

The ratio of the amount of EMR reflected by a body to the amount incident upon it, expressed as a percentage.

Alluvial fans:

Depositional landform features produced by surface streams laden with sediment, usually when exiting a narrow valley onto a less steeply sloping surface. Semi-circular fan shape occurs as stream travels to left and right of deposited debris.

Anticlinal fold:

Horizontal rock strata when folded into an upfold produce an anticline which may appear at the surface as a ridge.

Apollo, Mercury, Gemini:

NASA's Mercury Project (May, 1961 to May, 1963) demonstrated man's ability to withstand space travel. Gemini Project (1964 to 1966) was the beginning of sophisticated manned space flight. The Appolo Project (1961 to 1973) achieved its major goal of placing a man on the Moon on July 20, 1969.

Area-specific stretch:

The enhancement of a particular part of an Image by means of modifying the histogram at specific gray levels.

Areal units of measure:

Units used to designate areas, e.g., square foot, acre, square mile, square centimeter, square meter, square kilometer.

ARGOS DCS:

A data collection and platform location system on the TIROS-N polar orbiter environmental satellite.

Arithmetic proportion:

A mathematical relationship wherein one ration equals another ratio, e.g., 1/2 = 2/4.

Atmospheric transmission:

The movement of radiation through the atmosphere.

Attentuation:

The loss of energy moving through space by absorption, scattering, and reflectance.

Average photo base length:

The average of the distance between the principal point and the corresponding principal point on successive photos within a flight line.

AVHRR:

Advanced Very High Resolution Radiometer sensor on the TIROS-N polar orbiter satellite is a 5 channel scanning radiometer which records imagery and quantitative radiance data at 1 and 4 km resolution.
Visit the AVHRR Home Page
See also:
AVHRR Ocean Pathfinder Home Page

Azimuth direction:

Parallel to the line of flight in radar imaging from aircraft.

Azimuth resolution:

The quality of resolving or seeing objects in radar images parallel to the line of flight.

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Bajada:

A bench-like surface formed at the base of mountains by the coalescing of alluvial fans.

Banding:

Cross-polarized radar images, HV or VH, are often affected by this phenomenon which produces parallel bands on the Image parallel to the line of flight.

Banding (striping):

When a sensor in a MSS system malfunctions, it will not provide the proper values, leading to stripes of constant gray values (black or other level) each time that sensors values are recorded.

Bands:

A selection or range of Wavelengths.

Barrier islands:

Islands that are formed parallel to a mainland coast where breaking ocean waves create sandbars that increase in size due to the impact of wind, waves, and ocean currents.

Beam width:

In radar imaging this is the width of the area "painted" by the radar energy. It is constant in Synthetic aperture radar and becomes larger with distance from the plane in "brute force" radar.

Binary digits (bits):

The most basic language of the computer is to recognize "0" electric circuit off, or "1" electric circuit on; the "0" and "1" are binary digits or bits.

Black and white infrared:

A single emulsion layer film that is sensitive to light from 2.5 to 9.0 micrometers and records images as black and white. A red filter is required for proper exposure.

Black and white Photography:

The production on film and paper print material of reflected energy as shades of gray (from black to white) within the visible and near infrared portions of the EMS.

Broad clusters:

Refers to an unsupervised classification scheme for a digital false color composite Image where pixels are grouped with the peak of a three dimensional histogram that is closest in value; nearest neighbor pixels are considered in this Idrisi module.

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Camera obscura:

A precursor to the modern camera; initially operated similar to a pinhold camera, projecting images through a pinhole without a lens.

CD-ROM:

Compact disc, read only memory; one disc hold up to approximately 540 megabytes of data, greatly increasing the accessibility of a PC or Mac computer for large images.

Central pivot agriculture:

A type of agriculture that uses an irrigation system that distributes water through a pipe that travels in a circle like the hands on a clock and produces distinctive, circular field patterns.

Change through time:

A powerful tool of analysis that can be documented by Photographic or other Image records of the Earth's surface.

CIR:

Color Infrared Photography.

CIR film dye lot:

This refers to the number of the batch of dye used in producing the film. Each batch of dye is a factor in the particular range of colors recorded by the film. The number is printed on each box containing CIR film.

CIR signatures:

Objects recorded on CIR film will display particular types of false color patterns that are replicable, especially with regard to types of vegetation, and can be used to aid identification.
See Also:
CIR Videography
Identification Log
LU/LC Signature
Mental Library
Signature Characteristics
Signature Identification

CIR videography:

The process of recording a scene or area on videotape in the color signature common to color infrared film.
See Also:
CIR Signatures
Identification Log
LU/LC Signature
Mental Library
Signature Characteristics
Signature Identification

CIR window:

The period of time in the spring and fall seasons of the middle latitudes when some but not all vegetative growth is ongoing. It is the time when the widest range of colors and hues may be recorded on CIR film and make differentiation of phenomena easier.

Civil Engineer's scale:

A measuring rule of six cales showing inches divided into 10, 20, 30, 40, 50 and 60 parts.

Classification factors:

Some of the parameters that impact the classification of similar areas of land use or land cover are that classes be mutually exclusive, homogeneous, and consistently interpretable within the limitations of Scale and seasonal variation in cover.

Cluster analysis:

A technique of Image classification in which histogram peaks of pixel values are identified by the computer and which are then used to group pixels with similar values.

Coastal Zone Color Scanner (CZCS):

An instrument on Nimbus-7 designed to measure chlorophyll concentrations and color variations in ocean water around the world.

Color infrared (CIR):

A false color rendition of light recorded within the visible and reflected infrared portions of the Electromagnetic Spectrum.

Color infrared Photography (CIR):

The production on film and paper print material of reflected energy in the visible and near IR portions of the EMS as false color images.

Color Photography:

The production on film and paper print material of reflected energy in the visible portion of the EMS of colors as seen by the human eye through the use of blue, green, and red-sensitive dye layers.

Compatible land uses:

In planning theory, the concept that certain types of use of the land can exist in economic and social harmony, e.g., residential areas and cemeteries, whereas other combinations are incompatible, e.g., country club and an active landfill.

Compensating polar planimeter:

A device used to trace the circumference of a feature (lake, forest, etc.) on a map or photo and yields the area in square inches or square centimeters. May be mechanical or digital.

Complex dielectric constant:

A value controlled by the electrical properties of a surface material and is an inication of likely reflectance or penetration capabilities.

Contact prints:

A Photographic print made at the same size as a film negative or film positive through contact during reproduction.

Contour:

see examples of contour maps at The USGS (You'll need Shockwave)

Contrast stretching:

Refers to a group of image enhancement techniques that are used to increase contrast invarious parts of a histogram of pixel values, thus rendering greater clarity of detail.
See Also:
Seamless mosaicing

Controlled mosaic:

A series of overlapping airphotos that have been rectified and aligned with ground control points so that accurate measurements of distance may be made directly on the mosaic.

Corresponding principal points (CCP):

Also referred to as conjugate principal point. The location of a principal point from one photo on the succeeding photo in a flight line.

Cross polarization:

In radar imaging, energy that is transmitted in vertical or horizontal wave motion returns to the aircraft in the opposite configuration, H to V or V to H.

Culture:

Any artifacts or works of people as seen on maps or photos.

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Daily Weather Maps:

Surface weather maps of the United States that are a compilation of 7AM EST conditions of the atmosphere across the USA.

Density slicing:

A computer process that converts an Image into a series of levels or steps of gray tones so that patterns or shapes are more easily recognized.

Depression angle:

The angle between a horizontal at the aircraft and the target of a radar beam.

Desktop publishing:

The use of a computer to prepare text, graphics, and pictures in digital form for the printing process.

Detection:

Quality of a remote sensor to distinguish an object on an Image; the smallest feature that can be distinguished.

Dichotomous key:

A form of elimination key in airphoto identification wherein the user is faced with a series of choices between two alternatives until the correct identification is made.

Differential parallax:

The difference in displacement between ground points of different elevation on overlapping photos, e.g., the measured distance between the top of a chimney on one photo to another subtracted from the distance between the bottom on one to the bottom on the other.

Diffuse reflection:

A radar beam striking a rough surface will produce reflection in many directions and yield a strong return.

Digital Image

Digital numbers (DNs):

The values of each pixel in an Image based upon the intensity of the field recorded.

Digital Orthophoto Quads:

See:

Index to Texas DOQs

Digital terrain maps:

Topography on tapes in digital form that was derived from 1:250,000 Scale USGS maps; useful in applications that employ slope map and terrain profiles; available from USGS.

Directional filters:

Computer operations designed to enhance specific linear features in an Image.

DMSP Visible-IR:

Defense Meteorological Satellite Program of the U.S. Air Force acquires images 24-hours a day in the visible-near IR as well as a thermal band.

Doppler principle:

A statement of the changes in Wavelength or frequency of energy generated by a moving object with reference to a target.

Dot grids:

An overlay device for arriving at a quick estimate of area of some feature on a photo by counting dots. Dots may be regularly spaced or random.

Drafting tape:

A tape used in cartographic or architectural drafting which appears similar to masking tape, but has less adhesive material and is less damaging to surfaces.

Dry plate process:

The production of a Photographic film emulsion by George Eastman that used gelatin in place of wet emulsions.

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Earth as closed system:

The concept that the Earth and its environment are in reality one large ecosystem; actions that impact one part of the system will eventually impact the remaining parts.

Earth Observing System (EOS):

Part of the Mission to Planet Earth Program; includes 25 NASA sponsored instruments and others scheduled for deployment from 1998-2015.

Edge enhancement:

A group of image enhancement techniques that are designed to increase the contrast along the edges of linear features so that they are easier to see.

8-bit, 256 levels:

Currently the most common form of digital images is an 8 bit system which provides 256 levels of gray, from 0 = black to 255 = white.

Electromagnetic radiation (EMR):

Energy that travels through space or materials in harmonic wave patterns (of consistent length) including the interaction at right angles of electric and magnetic fields.

Electromagnetic spectrum (EMS):

A continuum of energy or an ordered array that extends from the shortest cosmic rays, gamma rays, and X-rays to visible radiation, infrared radiation, and the longest microwaves and radio waves.
See also:
Radio Spectrum

Elimination key:

A form of airphoto identification in which the user in confronted with general choices for identification and then another set of choices until only one type of identification remains.

Enhancement: See Also: Image Enhancement

EOSAT:

Earth Observation Satellite Company is the quasi-public firm that distributes Image products for the Federal government at EROS Data Center, Sioux Falls, SD and other centers.

EROS Data Center (EDC):

The main distribution center and archive for airphotos and satellite imagery maintained by the U.S. Department of the Interior, U.S. Geological Survey, at Sioux Falls, SD 57198.

Jump to the EROS Data Center (US Geological Survey)

EROS:

Satellite (see Landsat
For examples see:
The Best of EROS

Erosional remnants:

Resistant landform features that remain after an area has been subjected to weathering and erosion, e.g., monadnocks, nunataks, and inselbergs.

ERTS:

Earth Resources Technological Satellite, the early name for what came to be knows as Landsat.

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False color:

The range of colors used to represent a scene in a form other than what would normally be perceived by the human eye. The most common example is CIR, color infrared Photography.

false color composite:

Refers to the combining of several bands of Photography or imagery with colors that do not replicate normal human vision. The most common form produces color responses similar to color infrared.

Fiducial marks:

Marks that are built in to aerial cameras and appear on each photo acquired in the corners or sides or both, and are used to determine the precise location of the principal point.

Fine clusters:

Refers to the grouping of pixels in an unsupervised classification of a digital false color composite Image by comparison of pixel DNs with histogram peaks in a relaxed nearest neighbor approach' an Idrisi module as applied here (the text).

Forward overlap:

The amount of overlap between successive photos in a flight line to aloow for steroviewing' usually 60-70%.
See Also:
sidelap

French long lot:

Also called arpent system' a form of land partition in which long, narrow pieces of property had their frontage on a river rather than on a street' distinctive pattern found where French colonized during the past 200 years.

Frequency:

The number of wave crests passing a given point in a specific period of time, e.g., cycles per second.

Full disc infrared Image:

A thermal image of all of the Earth that can be viewed from the GOES satellite.

Full disc visible image:

A visible Image of the entire Earth as seen from the GOES satellite.

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Gaussian stretch:

A form of Image enhancement that forces pixel DNs into a normal curve thus increasing overall scene contrast.

Geographic registration:

Process of superimposing two or more images so that points on the Earth's surface coincide on the final image product.

Geostationary:

A satellite whose orbit and speed allows it to maintain a position above the same location on the Earth's surface.

Global Change Research Program:

An international effort to study changes in the Earth's atmosphere and surface conditions that includes the effort of several U.S. agencies such as NASA and NOAA.

GOES satellite:

Normal operation calls for 2 Geostationary Operational Environmental Satellites positioned 22,300 miles above the Equator at 75 and 135 degrees west longitude. They provide continuous weather imagery of the entire conterminous United States.

Graphic or bar Scale:

One manner of presenting linear Scale on a map; a line is divided into scaled units for direct measure on the map, e.g., feet, miles, kilometers.

Great valley:

The open portion of the Ridge and Valley Province that extends from the Hudson River south of Albany, NY to Birmingham, AL.

Grazing angle:

In radar imaging, the angle at which the beam strikes the ground.

Ground control:

The location of specific points on the ground in terms of their horizontal and vertical location by means of ground survey.

Ground resolution cell:

The area on the ground that is covered by a pixel in a remotely sensed Image.

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Hand-held Photography:

Photographs taken from space on any of the manned missions, most often using a modified Haselblad 70mm camera.

Haze correction:

The visible bands of the EMS are subject to attenuation due to haze whereas the reflected IR are less affected. The histogram of the latter is used to correct that of the former.

Haze penetration:

The shorter Wavelengths of visible light are partially attenuated by atmospheric haze whereas Wavelengths of the reflected IR are able to pass through haze and be recorded.

High frequency areas:

Areas of an Image with great detail or many changes in brightness values.

High Oblique Airphotos:

An airphoto which shows the horizon line due to angle of view.
See Also:
Oblique Air Photos
Low Oblique
Vertical Air Photos

High-pass filters:

An electronic enhancement that enhances the detail in an Image.

High resolution visible (HRV)

Refers to the three multispectral bands at 20 meter resolution and the panchromatic band at 10 meters resolution of the SPOT program.
See Also:
Multispectral Classification
Multispectral Scanner
RASCAL, Flight Landata, Inc.
Spectral Bands

Histogram:

A graphic arrangement of the pixel DNs in a band of an Image, usually with the DN range on the X axis and the frequency on the Y.

histogram equalization:

In the Uniform Distribution Stretch of the DNs in a histogram to achieve uniform densityof pixels in all gray levels.

histogram peaks:

pixels tend to be grouped in clusters in a histogram leading to the formation of peaks representing areas in a digital image where values are similar, e.g., water area, forest area, etc.

Homogeneous sites:

Refers to the selection of Training Sites in creating a supervised classification of a composite digital image; groups of pixels are selected by the interpreter based upon knowledge of the study area; the pixels in each group should be homogeneous.

Horizontal polarization:

A radar pulse of energy that is transmitted and received from the target with horizontal orientation of microwaves.
See also:
Vertical Polarization

Hudson Highlands:

The name given for a section of the Taconic Mountain in lower New York state bordering the Hudson River.

Human/environment interface:

A focus for study in many disciplines, including the interpretation of airphoto and images, is the impact of the natural environment on human activity and of human actions upon the environment.

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IBM-compatible, PC environment:

Refers to one of the two major versions of individual computers, the system that was created by International Business Machines, Inc. and the clones that are compatible with that system.

IBM precision processing:

An Image processing system developed by IBM in the early 1970s that produced sharper images with a much wider array of colors than was available as a standard product from EDC at the time.

Image:

The representation of an object by means of a sensing system, a focusing system, and a recording medium and produced by optical, electro-optical, optical mechanical, or electronic means.

Image enhancement:

The manipulation of an Image in order to extract added data with a resulting loss of data elsewhere in the Image.
See Also:
Contrast Stretching
edge enhancement
Gaussian stretch
image restoration
non-linear stretch
Pre-press image processing
Sinusoidal Stretch
Spatial Filtering
Uniform Distribution Stretch
Unsupervised classification

Image "noise" or static:

Non-valid data that is introduced to recorded information during recording or transmission, e.g., banding in radar or line dropouts in MSS imagery.

Image restoration:

image enhancement procedures that are designed to remove the effects of "noise," the imperfect function of the sensing system, and the effects or vehicle instability.

Industrial Revolution:

The period from the middle of the 18th century through most of the 19th century when the methods of production, transportation, and communication were totally revamped.

Inselberg (Bornhardt):

The name of an erosional remnant in a mountainous, arid landscape.

Intermittent stream:

A river or stream that flows for only part of the year.

Intermontane region:

In the United States that area that lies between the Cascade and Sierra Nevada Mountains on the west and the Rocky Mountain system on the east.

Internet:

An international computer network maintained by national governments and easily accessible by an individual with a computer and a modem.

Interpretation log:

A record of Image signature and other information that has been derived from an airphoto steropair, or stereotriplet.
See Also:
CIR Signatures
CIR Videography
LU/LC Signature
Mental Library
Signature Characteristics
Signature Identification

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Ka, X, L band radars:

Refers to Wavelengths of side-looking airborne radar systems of 0.8-1.1, 2.4-3.8, and 15-30 cm., respectively.

Karst topography:

A type of landscape that develops in areas of the world where there are layers of limestone rock underlying the surface and sufficient rainfall or groundwater flow to dissolve the rock.

Kodacolor Aero Reversal Film:

An aerial film that is used in a positive to positive Photographic process, similar to the production of 35mm slides.

Kodachrome CIR:

A 35mm film that may be used to produce positive slides that portray false color infrared display. Requires the use of a wratten #12 minus blue filter.

Kodak No. 1:

The camera produced by George Eastman in 1888 that opened the field of Photography to the layman.

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Land cover:

Usually used to denote the nature of the Earth's surface in areas where the natural environment is dominant.

Landsat:

A series of unmanned satellites that began recording the Earth's surface in 1972 in multiple Wavelength bands. It is ongoing.
See also:
More (U of Waterloo, Canada)
The Landsat Program
Landsat Photos of the USA
Austin Texas (205 Kb)

Land use:

The nature of the Earth's surface in areas where the human imprint upon land is dominant.

land use/land cover maps:

Maps produced by the USGS and other agencies that delineate areas of common use or cover.

LU/LC signatures:

The collection of characteristics related to the land use and/or land cover of a feature that together allow its identificaiton.
See Also:
CIR Signatures
CIR Videography
Identification Log
Mental Library
Signature Characteristics
Signature Identification

Large format camera:

A special camera created for the Space Shuttle that acquires 9" x 18" contact photographs of the Earth.

Large Scale vs. small Scale:

Large Scale maps or images show great detail for a small ground area, whereas small scal products portray less detail for a larger area, e.g., RF 1:10,000 = large Scale; small Scale = RF 1:500,000.

Layover:

radar images portray the displacement of the tops of mountains and features projecting above the landscape towards the sensor.

Leaf on/leaf off:

Refers to aerial Photography taken to portray an area when vegetated or when trees are bare of leaves, one or the other is required depending upon the ultimate use of the Photography.

Linear distance vs. area:

Two methods of relating the Scale of a map to another map or to the surface represented, e.g., RF 1:5,000 represents linear distance between objects twice as long as on a map of RF 1:10,000, but covers one-fourth the area.

Linears (lineaments):

Line features on an Image that may be faults, roads, or railroads, etc., on the surface recorded.

Linear stretch:

A group of enhancement procedures that allows for the increase in contrast of a digital image while maintaining the original brightness relationships.

Linear units of measure:

Units of measurement along a line, e.g., inch, foot, mile, centimeter, meter, or kilometer.

Line dropouts:

When a sensor fails or sticks, no DN values are recorded and this produces recurring black lines in an MSS image.

Loessial soil:

A fine, silt-loam deposited by wind that has the characteristic of forming steep slopes when eroded.

Look direction:

In radar imaging, the direction in which the beam is transmitted an at a right angle to the flight path.

Low frequency areas:

Parts of an Image characterized by few changes in brightness values or little change in detail.

Low oblique:

An airphoto that is tilted from the vertical view, but not enough to include the horizon in the photo.
See Also:
Oblique Air Photos
High Oblique
Vertical Air Photo

Low-pass filter:

An electronic enhancement of an Image that increases the general patterns or forms by suppressing detail.

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MacConnell's classification:

William P. MacConnell of the Department of Forestry, and Wildlife Management at the University of Massachusetts created a classification of land use/land cover at Scale of RF 1:24,000 based upon airphoto interpretation in order to map the state's wildlife habitat.

Macintosh environment:

One of the two major version of individual computers; this one created by Apple and dominant in education below college level.

Map measurer:

An instrument used to trace an irregular linear distance. Reads in inches or centimeters. Also known as an opisometer.

Maximum likelihood:

A method of supervised classification of a digital image false color composite related to the probability that a pixel DN would be assigned to a particular classification, in this instance as performed by Idrisi software.

Medical imaging:

An extremely sophisticated field that borrowed early techniques and algorithms from those developed in remote sensing. It is now possible to record images of the brain, other organs, and even the valves on an operating heart without invasive procedures.

Mental library:

Refers to the remembered Image signatures which assist someone in identifying features on airphotos or other images.
See Also:
CIR Signatures
CIR Videography
Identification Log
LU/LC Signature
Signature Characteristics
Signature Identification

Minimum distance to means:

A method of supervised classification of a digital image false color composite where each pixel DN is placed in a class based upon its closeness to the mean of the class, in this instance as performed by Idrisi software.

Mirror stereoscope:

An optical instrument that is equipped with first surface mirrors and prisms to allow the viewing of successive photos in flight line without overlap, to produce a mental 3D image.
See Also:
Pocket Stereoscope

Mission to Planet Earth (MTPE):

A NASA program that is part of an international effort to study processes that determine Earth climatic change.

Modem:

A device used to connect a computer with another computer or a network via a telephone connection; may be external or internal to the computer.

Modification of physical and cultural landscapes:

Changes in physiography and cultural landscapes such as land use, urban systems, and economic distributions are often revealed by the study of airphotos and satellite images covering a period of time.

Mosiac:

The arrangement of airphotos in a series of overlapping exposures within a number of overlapping flight lines.
See Also:
Controlled mosaic
Uncontrolled mosaic
Orthophoto mosaic
Photo index mosaic
Seamless moasiacing
Sun angle correction
USGS Topographic maps

Multi-band sensing:

Acquiring several bands of reflected/emitted data from a target greatly increases the amount of informatio available and the analytic capability.

Multi-sensor approach:

Acquiring several bands of reflected and/or emitted energy from a target on a single overflight.

Multispectral classification:

A procedure that deals with information extraction from a digital image' usually three or more bands that hold most of the variation in an Image are used to create a false-color composite which is subjected to a variety of statistical applications.
See Also:
High Resolution Visible (HRV)
Multispectral Classification
Multispectral Scanner
RASCAL, Flight Landata, Inc.
Spectral Bands

multispectral Scanner (MSS):

The scanning system of Landsat that acquires four registered bands of reflected energy in the visible and near IR.
See Also:
High Resolution Visible (HRV)
Multispectral Classification
RASCAL, Flight Landata, Inc.
Spectral Bands

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Nadir:

The point on the ground that is directly beneath the aerial camera and lies on a vertical between the camera and the center of the Earth.

NAPP Photography:

National Aerial Photography Program began in 1987 and is ongoing. All of the contiguous United States will be photographed at RF 1:40,000 Scale in CIR. Each photo covers one-half of a USGS topographic quadrangle.

NASA:

National Aeronautics and Space Administration.

Natural color:

The range of colors that would be perceived by the human eye as replicated in a photo or Image.

Nearest neighbor analysis:

A type of matrix or digital image analysis that examines the DN of a pixel and those of nearby pixels to determine if there is a statistical relationship that makes clustering of pixels logical, or leads to some other modification of pixels.

Negative-positive process:

The process of recording a negative Image of some object or scene and then producing a positive Image through chemical steps; originate din 1830s by William Henry Fox Talbot and is the forerunner of modern Photography.

Nephanalysis:

The study of cloud patterns and forms as a means of understanding and predicting weather.

NIMBUS:

The Latin word meaning cloud identifies an experimental research and developmental spacecraft.

NHAP Photography:

National High Altitude Program extended from 1980-1987 and was intended to cover the USA with CIR at RF 1:58,000, each Photography records the area of one USGES topographic quadrangle. Black & white Photography at 1:80,000 Scale was also acquired.

NOAA:

National Oceanic and Atmospheric Administration.

NOAA, NESDIS:

NOAA, National Environmental Satellite, Data, and Information Service with headquarters in Suitland, MD.

Non-linear stretch:

An image enhancement technique that allows for the variable modification of pixel DNs as opposed to linear stretch.

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Old age desert mountains:

Also referred to as inselbergs or bornhardts; erosional remnants buried in their own eroded debris.

Old age rivers:

A river system that has eroded downwards to near base level and exhibits features such as a floodplain several times wider than the meander belt, meander scars, oxbow lakes, levees, and Yazoo streams.

Oblique airphoto:

An airphoto that was acquired with a view of the ground that was not vertical.

Operational Line-scan System (OLS):

The scanning system on board the U.S. Air Force DMSP satellite operates in a visible-near IR band and a TIR band.

Orthophoto:

A vertical aerial photograph which has been rectified to remove parallax.

Orthophoto mosaic:

A series of overlapping orthophotos that photographically cover a specified ground area.

Orthophotoscope:

The optical instrument that is used to rectify vertical airphotos in order to remove parallax.

Palisades:

An area of nearly vertical basalt columns exposed along the west bank of the Hudson River just north of New York City.

Panchromatic:

Black & White film that is sensitive to all visible Wavelengths of light.

Paper straight edge:

Refers to using the straight edge of a piece of paper to mark the straight line distance between two points on a map; can then be converted to miles or kilometers by direct comparison to the map's graphic scale.

Parallax:

The displacement of objects on airphotos as a result of their position with reference to the ground datum and the center of the photo.

Passive system:

A remote sensing system that records the existing reflected or emitted energy leaving a target.

Patterns and processes:

A frame of reference that is useful when interpreting landforms and natural features is to relate the features to noteworthy patterns or distinctive steps in a process of change.

PE&RS journal:

The official journal of the American Society for Photogrammetry and remote sensing and formerly titled, Photogrammetric Engineering and remote sensing.

Photogrammetry:

The science of obtaining reliable measurements through the medium of Photography.

Photograph:

An Image formed on a base material through the action of light on a sensitized emulsion and produced by means of chemical steps.

Photographic process:

The procedure of recording reflected light on a light sensitive emulsion and then producing an Image by means of chemical steps.

Photographic spectrum:

That portion of the Electromagnetic Spectrum that may be recorded on film.

Photo index mosaic:

An uncontrolled mosaic of airphotos arranged to show the coverage of the ground while illustrating exposure numbers of the various parts of the area.

Physiographic regions:

Areas of the Earth's surface that are homogeneous in rock materials, formations, or processes that produced the landforms therein.

Picture elements:

The smallest units of data in a digital image, pixels.

Pixel:

Short for "picture element," the smallest unit of data in a scanned satellite Image.

Plan position indicator (PPI):

radar images produced by a rotating antenna so that a cathode ray tube displays return from an area surrounding the radar system, e.g., local weather radar.

Plunging anticline:

An anticline that when folded was also titled to that it disappears beneath the present surface at one end of the ridge.

Plunging syncline:

The remnants of a downfold that now extends above the surface' when folded it was also tilted so that the feature disappears beneath the existing ground surface at one end.

Pocket stereoscope:

An optical device that allows one to view the same ground area on adjacent, overlapping airphotos to produce a mental 3D image.
See Also:
Mirror Stereoscope

Polarity of gray tones:

It is possible to create thermal images with either white or black representing coldest or warmest temperatures and so caution in interpretation is required.

Polar orbiters:

Satellites that follow a near polar orbit and as the Earth rotates beneath the satellite it scans new areas on each pass.

Positive identification:

Sufficient evidence has been gathered to allow for certain identification of objects of features on an Image .

Pre-press Image processing:

Techniques of image enhancement used in the publishing industry; changes in contrast, color, or any element on an Image designed to attain a particular effect of visual impact.

Principal components analysis:

A statistical technique that compares the bands in a digital image to determine which one portray most of the variation in data in the Image; fewer bands may then be used in Image enhancement/classification, saving time and reducing cost.

Principal point (P):

The center of a vertical airphoto; it is assumed to be the photo location of the nadir.

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Radar:

Radio detection And Ranging, an active remote sensing system that sends out an electronic pulse and records returned energy.
See also RadarSat.

Radar return:

The energy from a radar beam that strikes an object and is reflected back to the sensing device.

Range resolution:

The quality of distinguishing between objects on a radar system in the look direction.

RASCAL, Flight Landata, Inc.:

Remote Airborne Sensor Computer Analysis Link; a multi-spectral video imaging system that produces real-time CIR video as well as the individual bands' can be fine tuned for very specific band selection.
See Also:
High Resolution Visible (HRV)
Multispectral Classification
Multispectral Scanner
Spectral Bands

Raster image:

A digital image consisting of pixels arranged in rows and columns.

Ratio images:

An Image produced by dividing the pixel DNs of one band by the DNs of the same pixels in another band; enables the effects of topography (shadow vs bright) to be minimized.

Rayleigh criterion:

A statement of the relationship between radar Wavelength, surface roughness, and depression angle that affects the nature of the radar return.

Real aperture radar:

Also known as "brute force" radar in which the asimuth resolution is related to the length of the antenna and increasing beam width.

Real time CIR video:

This refers to videography that produced CIR color rendition as it was being acquired.

Rectified airphotos:

Photos that have had the effects of tilt and terrain relief removed.

Reflected infrared:

The near and middle infrared portion of the EMS, 0.7 to 3.0 micrometers.

Remote sensing:

The measurement and analysis of objects without physical contact between the sensing device and the target; includes all the areas of investigation in the text.

Representative Fraction:

The relation between linear distance on a map or photo and ground distance expressed as a fraction, e.g., 1/25,000 or 1:25,000 (where 1 inch on the map represents 25,000 inches on the ground).

Resolution:

The ability of a remote sensor system to separate or distinguish objects on an Image; sometimes expressed as line pairs per inch or per millimeter.

Return Beam Vidicon (RBV):

A sensing system on the first 3 Landsat vehicles that recorded black & white visible information in a form somewhat similar to a television picture.

Ridge and furrow agriculture:

An intensive form of agriculture of southeast Asia in which trenches are dug for irrigating rice and the soil removed from the furrow is piled on an adjacent ridge whre crops such as plantain are grown.

Ridge and valley:

A physiography region of the Appalachian area of the United States lying between the Appalachian Plateau to the west and the Great Valley to the east.

Rotures:

The division of land in the French long lot system in which land had narrow frontage on a river.

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Sampling procedures:

Refers to a large body of scientific methodology in which a sample of a larger matrix of data or of a larger area is used to arrive at conclusions about the whole.

SARSAT:

Search and Rescue System is one of the sensor systems on board TIROS-N.

Scale:

The relationship between distance on a map or photo to the corresponding distance between the same point on the Earth's surface.

Scale by comparison:

A method of determining the unknown Scale of a map or photo by comparison with a map of known Scale of the same area.

Scanner:

An imaging system that sweeps across the terrain in across-track or along-track direction, sensing a stream of pixel DNs.

Seamless mosaicing:

A form of splicing contiguous digital images together using geometric orientation and contrast stretching so that the boundary between scenes is not apparent.

Seasat:

A NASA satellite that was designed to provide data about ocean areas and operated for part of 1978 recording and sending back to Earth radar images and other information.

Section:

A square mile parcel that is the basic unit of a township in the U.S. Public Land Survey system.

Selective key:

A means of identification of objects on airphotos by comparison with representative images, drawings, Stereograms, etc. of typical features.

SEM:

Space Environment Monitor is a sensor on board TIROS-N.

Sequent occupance:

A geographic concept from the early decades of the 1900s in which the successive foci of economic activity in a region was studied in analyzing change, e.g., from farming, shipbuilding, textiles and leather manufacturing, to electronic industry in coastal Mass.

Shuttle imaging radar (SIR-A):

An L-band imaging radar that was operated from the NASA Space Shuttle in 1984.

Sidelap:

The amount of overlap between airphotos in adjacent flight lines, usually presented as a percentage.

Side Looking Airborne radar (SLAR):

Airborne radar that transmits a microwave burst of energy sideways from the plane and records the energy that is reflected back by surface targets.

Signature characteristics:

Defining parametes of a feature on an Image that collectively allow for its identification, e.g., size, shape, pattern, contrast, texture, shadow, color, reflectance, et. al.
See Also:
CIR Signatures
CIR Videography
Identification Log
LU/LC Signature
Mental Library
Signature Identification

Signature identification:

Using characteristics of a feature on an Image to identify it on subsequently examined images.
See Also:
CIR Signatures
CIR Videography
Identification Log
LU/LC Signature
Mental Library
Signature Characteristics

Sinkholes:

Holes in areas of karst topography where solution of underlying limestone has led to cave in of surface materials.

Sinusoidal stretch:

A form of image enhancement that is designed to provide more detail in areas of an Image that appear to have similar DNs.

Site factors:

Those characteristics of a specific location that have an impact on the nature of an Image of the area, e.g., roughness, shapes, texture, slope, etc.

Situation factors:

Those characteristics of the area surrounding a target that might give insight into the interpretation of an Image of the target, e.g., vegetative cover, landforms, cultural artifacts, etc.

Skylab:

An orbiting workstation that was utilized by 3 crews in 1973-74.

Slant range distance:

The straight line distance from a radar to its target.

Slope maps:

Selected locations in the United States have had slope maps produced by the USGS; they are useful in evaluating danger of flooding, soil erosion, landform stability, etc.

Soil marks:

In archaeology some vestiges of earlier use of land can be seen from airphotos where buried landscapes impact and produce patterns in the present surface of the ground.

Space Shuttle:

The commonly used name for NASA's Space Transportation System.

Space Transportation System (STS):

The official name for the U.S. Space Shuttle system.

Spatial filtering:

A type of image enhancement technique in which groups of pixels in close proximity have their DNs statistically examined to determine what Image modification may be made (see low-pass & high-pass filters).

Spectral bands:

Refers to specific Wavelength values that make up one band to be recorded or sensed by a satellite system.
See Also:
High Resolution Visible (HRV)
Multispectral Classification
Multispectral Scanner
RASCAL, Flight Landata, Inc.

Specular reflection:

A smooth surface produces a mirror-like reflection and in radar imaging results in no return and a dark area on Images.

SPOT program:

The unmanned French satellite system, Systeme Probatoire d'Observation de la Terre, that began operations in 1986.

Standard deviation units:

A statistical value that is used to describe the distance above or below the mean of a distribution that a particular observation lies.

Standard IR:

Refers to the TIR images most commonly acquired by the GOES satellite system.

Standard RGB array:

Is the typical means of producing color as it would be seen by the human eye, as opposed to false color.

Stereogram:

A Stereopair or stereotriplet of airphotos mounted for proper Stereovision.

Stereogram cards:

Card stock designed to be used for creating a Stereogram file.

Steropair:

Two overlapping, successive photos in a flight line aligned for steroviewing.

Stereovision:

Viewing two overlapping, successive airphotos in a flight line so that a three dimensional effect is produced.

Sunsynchronous:

A condition in which a satellite is place in a near polar orbit such that it passes over all places on the Earth's surface at the same latitude twice a day at the same local time.

Sun angle correction:

When joining images in a mosaic the sun angle in all the images can be made the same through mathematical manipulation of pixel DN values.

Superposed stream:

In geomorphology when a river has been flowing on a surface and is able to downcut fast enough to erode and underlying subsurface feature onto which it cuts down, it is termed "superposed".

Supervised classification:

An image interpreter identifies pixels or groups of pixels that are known to represent a specific type of land use, vegetation, etc., and then gives directions to the computer to locate all such pixels in the Image.

Synclinal fold:

In folded mountain topography the downfold or syncline can be isolated on a later erosional surface as a synclinal ridge or a synclinal valley and the forms may be interpreted on topographic maps and airphotos.

Synthetic Aperture radar (SAR):

The Doppler principle is employed to produce a synthetic antenna that operates as though it were much longer than a typical SLAR antenna, resulting in consistent resolution of objects in the asimuth direction.

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Taconic Mountains:

A section of the New England physiographic province that extends north-south on the east side of the Hudson Valley and reaches elevation of 2000 feet.

Thematic Mapper (TM):

The sensing system on Landsat 4 and after that acquired reflected and thermal data from the Earth's surface in 7 bands.

Thermal infrared:

The far infrared portion of the EMS, 3.0 to 15 micrometers, TIR.

Thermal Infrared images:

Images that display variations in tone or color that represent temperature differences.

TIROS, TIROS-N:

Television Infrared Operational Satellite operated by NOAA. The latest version is TRIOS-N or ATN, an advanced version. They are polar orbiters designated as NOAA-1, 2, etc. after they become operational. Many sensing systems on board.
For more information visit noaa.gov

TOMS:

Total Ozone Mapping Spectrometer sensor on board Nimbus-7 that studied the total column of ozone in the atmosphere.

Topographic inversion:

An optical illusion produced on images with shadows where ridges appears to be valleys and vice versa; usually corrected by orienting an Image so that shadows face the viewer.

TOVS:

TIROS Operational Vertical Sounder includes sensors that monitor atmospheric radiance in a number of bands to allow mapping of temperature and humidity levels.

Transects:

A method of Sampling in which a set of parallel, equidistant lines are drawn across a map or photo. Summation of Image information beneath the lines is used to predict values for the whole photo.

Triassic lowlands:

A small physiographic province of easily eroded sedimentary rocks that separates the New England Province from the older Appalachians in the area between the Hudson River across New Jersey to Virginia.

Training sites:

Areas of a digital image that are identified by an interpreter as representing a specific type of use, soil, rock, or vegetation type; used to give instruction to computer in supervised classification.

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Uncontrolled mosaic:

The overlapping of airphotos by means of aligning objects on the photos without the use of ground control points. Whole photos are used in index mosaics, while only the central portions of photos are used when more accurate representation of surface features is desired.

Uniform distribution stretch:

An image enhancement technique that is non-linear in form; results in the resistribution of DN values based upon frequency of occurrence.

Unsupervised classification:

A group of digital image enhancement techniques based upon statistical manipulation without guidance from the interpreter using Training Sites or similar information.

USGS Topographic Maps:

The conterminous United States has been mapped in contiguous quadrangles whose bounds are specific latitude and longitude values allowing for creation of a mosaic of maps for an area several map scales are available for maps that display topographic surfaces and almost all other surface features except movable or non-permanent phenomena.

USGS land use/land cover classification:

A classification published by the US Geological Survey designed to facilitate LU/LC mapping of products produced by aircraft and satellites; 3 levels of generalization.

US Public Land Survey:

The Land Ordinance of 1785 that divided the lands of the United States, other than the oridinal 13 colonies, into Townships and Ranges based upon a series of north-south principal meridians and east-west base lines.

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Vector image:

A digital image formed by lines that connect points of specific X and Y values, e.g., road or railroad lines, property boundaries.

Verbal scale:

A statement of the Scale relationship of a map or photo to the area it portrays, e.g., "1 inch equals 100 feet," or "1 centimeter represents 5 kilometers."

Vertical airphoto:

An airphoto acquired with the camera pointed directly at the nadir.
See Also:
Oblique Air Photos
High Oblique
Low Oblique
Orthophoto

Vertical polarization:

The microwave energy that is transmitted from the radar system and received from the target is oriented in waves in a vertical plane.

Video disc reader:

A device that captures Image data from a video disc (similar in size to an old 78 rpm phonograph record) and feeds it to a VCR/television setup.

VIFIS system:

Variable Interference Filter Imaging Spectrometer; a video recording system that allows for one flyover of a target and yields multiple bands of data from one videotape.

Visible spectrum:

That portion of the Electromagnetic Spectrum to which the human eye is sensitive.
See also:
Electromagnet Spectrum
Photographic Spectrum

VISSR:

Visible Infrared Spin-Scan Radiometer is the sensing system on the GOES Geostationary satellite and monitors in visible and TIR Wavelengths.

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Water vapor imagery:

The 6.7 and 7.3 micrometer bands are greatly affected by the presence of water vapor in the atmosphere and so are used to monitor it from the GOES satellites. The imagery data is complex and requires sophisticated interpretation.

Wavelength:

The distance from the crest of one wave to the crest of the next wave (or trough to trough); used as a means of ordering radiation in the Electromagnetic Spectrum.

Wet plate Photograph:

During the middle and late 1800s this was the most common Photographic procedure; glass plates were coated with a moist emulsion and the Image had to be recorded before drying was complete.