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| Earth Resources Observation and Science (EROS) |
Glossary H through L
NASA has modified standard off-the-shelf Hasselblad 70 mm cameras to operate in zero gravity aboard the Space Shuttle. A data recording module (DRM) has also been installed on each camera to record the date, time (Greenwich Mean Time), mission number, roll number, and frame number. The cameras utilize a 70 mm film format and operate with one of three lenses (50, 100, or 250 mm) to acquire high quality photographs through four viewing ports on the Shuttle.
HDTs are high density (high capacity) magnetic tapes.
The process of mosaicking adjacent parts of a map or image together into a single map or image. This process might require geometric adjustments to the image itself or the features within it so that matching occurs across mosaic seams.
Transmission of microwaves so that the electric lines of force are horizontal, while the magnetic lines of force are vertical.
Horizontal positional accuracy is based upon the use of USGS source quadrangles which are compiled to meet National Map Accuracy Standards (NMAS). NMAS horizontal accuracy requires that at least 90 percent of points tested are within 0.02 inches of the true position. The digital data are estimated to contain a horizontal positional error of less than or equal to 0.003 inches standard error in the two component directions relative to the source quadrangle.
HRPT data are full resolution image data transmitted to a ground station as they are collected. The average instantaneous field-of-view of 1.4 milliradians yields a HRPT ground resolution of approximately 1.1 km at the satellite nadir from the nominal orbit altitude of 833 km (517 mi).
The HRV instrument is a multispectral radiometer designed for SPOT spacecraft. The HRV instrument provides for high-resolution imaging in the visible and near-infrared portions of the electromagnetic spectrum. The first three SPOT satellites carry twin HRVs that operate in a number of viewing configurations and in different spectral modes.
Some of those viewing configurations and spectral modes include one HRV only operating in a dual spectral mode (i.e., in both panchromatic mode and multispectral mode); two HRVs operating in the twin-viewing configuration (i.e., one HRV in panchromatic mode and one HRV in multispectral mode); and two HRVs operating independently of each other (i.e., not in twin-viewing configuration).
Scientific study of the waters of the Earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of ground water.
The use of links between related words, graphics, or documents that allow the user to jump to associated topics or definitions when reading menus or help files.
The scientific study of the Earth's topologic configuration above sea level, especially the measurement and mapping of land elevation.
A format of data whose values are represented by 16-bit words. Data distributed as I*2 format can have values ranging between -32,768 to +32,767. This format is commonly used for digital elevation and other data which requires values higher than the 0 to 255 range available for 8-bit (byte) data used for many remote sensing satellite image data.
IFOV is the solid angle through which a detector is sensitive to radiation. In a scanning system this refers to the solid angle subtended by the detector when the scanning motion is stopped. The IFOV is commonly expressed in milliradians.
The IMDISP is an interactive IMage DISPlay utility for personal computers. It can be used to display and manipulate raster images on a PC's monitor screen, as well as being used to perform basic digital image processing tasks such as histograms and contrast enhancement.
When accessing raster images using IMDISP, the program requires the user to supply information about the size, type, and location the image file to be displayed. This information can be entered manually or can be provided in an ASCII label file. This label file can be located at the beginning of an IMDISP formatted image file or can be a separate file that points to the image file.
The IMDISP is public domain software developed by Mike Martin at NASA's Jet Propulsion Laboratory in Pasadena, California, and supported by the NASA Goddard Space Flight Center in Greenbelt, Maryland.
Intercept is the distance from the origin to the point at which a curve or line crosses an axis.
To insert a value between known values by using a procedure or algorithm specifically related to the known values.
The ISO is a specialized international agency established to maintain standardization. Over 85 countries are participating members. Only one organization from each participating country may be a member. As an example ANSI is the United States member body. Members contribute to technical committees and vote for or against the approval of developed standards.
The ISO 9660 standard is the currently accepted industry standard for Compact Disc-Read Only Memory (CD-ROM). This standard assures the generation of CD-ROMs whose format is compatible with a multitude of computer platforms supporting IBM compatible DOS, Apple Macintosh, and Unix operating systems.
A method of drawing figures and maps so that three dimensions are shown not in perspective but in their actual measurements.
A line on a map connecting points at which a given variable has a specified constant value.
This destructive analytical technique is used to determine concentrations of specific chemical elements based on their rates of molecular diffusion in a gaseous or vaporous mixture. A known quantity of the chemical element in question is added to the mixture. This quantity, referred to as a tracer, is monitored to measure its diffusion rate.
Isotopic age, also referred to as radiometric age, is an age of rocks expressed in years and calculated from the quantitative determination of radioactive elements and their decay products.
The JNC series provides worldwide coverage at 1:2,000,000 scale. The information on these charts are suitable for aeronautical long-range, high-altitude, high-speed travel; map features include cities, roads, railroads, lakes, principal drainage, and permanent snow/ice areas. The polar regions are in a Transverse Mercator projection. All other regions are presented in the Lambert Conformal Conic projection.
A Kelvin Unit refers to a thermometric scale in which the degree intervals are equal to those of the Celsius scale and in which zero(0) degrees equals -273.15 degrees Celsius (absolute zero).
LAC are full resolution data that are recorded on an onboard tape recorder for subsequent transmission during a station overpass. The average instantaneous field-of-view of 1.4 milliradians yields a LAC ground resolution of approximately 1.1 km at the satellite nadir from the nominal orbit altitude of 833 km (517 mi).
Azimuthal projections are formed onto a plane which is usually tangent to the globe at either pole, the Equator, or any intermediate point. The Lambert Azimuthal Equal Area projection is a method of projecting maps on which the azimuth or direction from a given central point to any other point is shown correctly and also on which the areas of all regions are shown in the same proportion of their true areas. When a pole is the central point, all meridians are spaced at their true angles and are straight radii of concentric circles that represent the parallels.
This projection is frequently used in one of three aspects: The polar aspect is used in atlases for maps of polar regions and of the Northern and Southern Hemispheres; the equatorial aspect is commonly used for atlas maps of the Eastern and Western Hemispheres; and the oblique aspect is used for atlas maps of continents and oceans.
The Lambert Conformal Conic Projection is derived by the projection of lines from the center of the globe onto a simple cone. This cone intersects the Earth along two standard parallels of latitude, both of which are on the same side of the equator. All meridians are converging straight lines that meet at a common point beyond the limits of the map. Parallels are concentric circles whose center is at the intersection point of the meridians. Parallels and meridians cross at right angles, an essential of conformality.
To minimize and distribute scale errors, the two standard parallels are chosen to enclose two-thirds of the north to south map area. Between these parallels, the scale will be too small, and beyond them, too large. If the north to south extent of the mapping is limited, maximum scale errors will rarely exceed one percent. Area exaggeration between and near the standard parallels, is very slight; thus, the projection provides good directional and shape relationships for areas having their long axes running in an east to west belt.
The Landsat program, first known as the Earth Resources Technology Satellite (ERTS) Program, is a development of the National Aeronautics and Space Administration (NASA) in association with NOAA, USGS, and the Space Imaging. The activities of these combined groups led to the concept of dedicated Earth-orbiting satellites, the defining of spectral and spatial requirements for their instruments, and the fostering of research to determine the best means of extracting and using information from the data. The first satellite, ERTS 1, was launched on 7/23/72. The second satellite was launched on 1/22/75. Concurrently the name of the satellites and program was changed to emphasize its prime area of interest (land resources). The first two satellites were designated as Landsats 1 and 2. Landsat 3 was launched on 3/5/78. Landsat 4 was launched on 7/16/82. Landsat 5 (launched 3/1/84) is currently in service providing selected data to worldwide researchers.
The LAS is an image analysis system designed to ingest, manipulate, and analyze digital image data by providing the user with a wide array of functions and statistical tools. LAS supports research and production for remote sensing, image processing, and geographic information systems (GIS). It provides a flexible framework for the processing and the analysis of image data as well as for algorithm development. It is the main software system for the production image processing capabilities at the U.S. Geological Survey's EROS Data Center (EDC).
A LAS image header contains descriptive information about an image file. This header is located in the first 512-byte record of the image file. This information record is mandatory for all LAS images accessed directly from computer or optical disk.
Level 1b is considered raw quality controlled data configured into discrete data sets and to which Earth location and calibration information have been appended, but not applied.
The LFC was a high altitude aerial mapping camera scaled up to operate from the Space Shuttle in Earth-orbital altitudes. LFC specifications included:
-Film Format Size: 9 x 18 inches (23 x 46 cm) -Lens Aperture: F/6.0 -Lens Focal Length: 12 inches (30.5 cm) -Exposure Interval: 7.5 sec. -Exposure Range: 1/250 to 1/31.25 seconds -Ground Resolution: 20 meters at 160 nautical miles -Ground Coverage: 120 x 240 nautical miles at 160 n.m.
NASA has modified the Linhof cameras to operate in zero gravity on board the Space Shuttle. The camera utilizes a five-inch film format and is equipped with interchangeable lenses (90 mm and 250 mm). A data recording module (DRM) is also mounted on the camera to record the date, time (Greenwich Mean Time), mission number, roll number, and frame number for each photograph. The Linhof camera is used to acquire earth-looking photography through four viewing ports on board the Shuttle.
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