R
radiance
"Radiant brightness or light: the radiance of the tropical sun" (Random House).
radio button
A type of toggle button in a group of toggle buttons where only one of the toggle buttons can be on at a time. A radio button is preceded by a graphic indicator of the state of the button.
RAM
Random Access Memory. Read/write memory for programs and data that the computer uses as a general work area. The more RAM in a computer, the more general work space it has and the larger the projects it can handle. High speed RAM can be added to a computer with memory expansion boards. The RAM work area is accessed by numbered addresses that point to chunks of 1024 bytes (a kilobyte or K). Standard DOS-based PC architecture limits the RAM a computer can directly "see" to 640 K. Display boards generally have their own memory and do not use system RAM.
RAM disk
RAM beyond the standard 640 K that is reconfigured to work like a very high speed disk drive. DOS provides the VDISK command for setting up a RAM disk (VDISK is documented in the DOS reference manual). Some microcomputers do not allow a RAM disk in the memory in the address range between 640 K and 1024 K since it is used for DOS functions.
DOS uses a RAM disk just as it does any other disk drive. But since a RAM disk is not a true magnetic storage device, its contents are lost when the microcomputer is rebooted. Any permanent files must be copied from a RAM disk to a magnetic disk before turning off or rebooting the computer.
range extraction
A method of converting a grayscale raster object into a binary version. In range extraction, two boundary values are selected to bracket the desired range of grayscale values. Everything above and below the boundary values is set to 0 (black), while everything between the boundary values is set to 1 (white).
raster or raster object
A single, related, two dimensionally grouped set of numbers of a single data type. Each number represents the value of some parameter. Its position in the group represents its relative position to the other values. A raster object is a raster that is stored in an RVC project file.
raster algebra
Manipulations and functions that operate on raster objects cell by cell. Any raster object can be used as a variable, or operand, in a raster algebraic expression. You just set up a combination of operands in an equation and then assign a raster object to each operand. The result of the operation is stored in a new raster object.
raster cell
One value in a raster that corresponds to a specific area on the ground. A raster cell value may be the elevation above sea level at one position in a survey site or the intensity of red radiation for a pixel in a video image. For convenience, a raster cell is usually thought of as square or rectangular, although many image collection devices actually measure circular or elliptical areas.
raster space
The area of a raster object stored in an RVC project file. This area can be very large, up to 2,000,000,000 by 2,000,000,000 cells.
RAT
Route attribute table. A RAT stores route attributes. There is one RAT for each route-system in a coverage.
RDBMS
Relational Database Management System. A database management system with the ability to access data organized in tabular files that can be related to each other by a common field (items). An RDBMS has the capability to recombine the data items from different files, providing powerful tools for data usage.
record
A database organized into tables, which contain records. Each record supplies information gathered for an individual example. Records contain one or more fields related to the topic of the table in which they are found. For instance, the Crow Butte soil polygon database has a table of crop potentials, and there is a record for each soil type. (See also: database, field, table.)
rectification
Removing geometric distortion from a raster or a vector object. Rectification is usually achieved by aligning raster features or vector coordinate positions with features in a base map or other coordinate reference framework. Rectification may be used to bring several distorted image segments into a common framework so they can be combined into a larger image.
reference image
An image on the display monitor used for visual reference that is generated by (or otherwise corresponds to) a raster object or set of raster objects. That is, you can use one raster object for the display, and another raster object or set of raster objects for processing. In the simplest case, you use the same raster object for both the processing raster object and your reference on the display. In a more complex case, you use one raster object for the display image, and a whole set of raster objects for processing. (The processing set may include the display raster.) For instance, you could use a raster object with a composite natural-color image of the study site for the display, while using the seven raster objects containing the spectral bands of the Landsat Thematic Mapper data for processing. (See also: processing rasters.)
region of interest
(Feature Mapping) Defines the area of the input raster objects to be considered for all subsequent processing while that region is selected. A selected region of interest affects the categories that can be defined, limits the area in which cells that satisfy the decision rule are searched for, and defines the region of the feature mapped raster for which measurements are tabulated in Feature Mapping's statistical report. Feature marking is also limited to the region of interest. (See also: categories, feature mapping.)
registration
Geometrically aligning sets of image data such that corresponding features are coincident. (See also: coregistration.)
regression line
A line that best describes all the data points using a particular method of error estimation, such as least squares.
relief
(as in shaded relief) The variation in a raster object's values that shows differences between a surface's higher and lower parts in elevation and slope.
Remote Sensing
Acquiring information about an object without contracting it physically. Methods include aerial photography, radar and Satellite Imaging.
render
Create an electronic or hardcopy representation, particularly of an outline font. When an outline font is rendered, it assumes a fixed size and shear angle on the screen, raster, or hardcopy to which it is rendered.
resample
To interpolate cell values in a raster object and create a raster with larger or smaller cells. (See also: interpolation.)
resize
To change the height and/or width of a window.
resolution
The level of object detail or sharpness determined by how many picture elements compose an area of a display or corresponding raster. Resolution may refer to sensors, raster objects, or displays. Low resolution display devices produce images with a grainy visual texture. High resolution displays use such small picture elements that they can produce a near-photographic quality image. (See also: ground resolution.)
resolution
(digitizer) The smallest movement that can be detected by the digitizer. Resolution is usually expressed in either measurement units (.001") or dots-per-inch (1000 dpi).
restitution
The determination of the true (map) position of objects or points; the image of which appears distorted or displaced on unprocessed aerial photographs. Restitution corrects for displacement resulting from both tilt and relief displacement. Restitution in classic photogrammetry is commonly achieved by analytical methods or through the use of stereoscopic plotting instruments.
RGB
Red, Green, and Blue. The red-green-blue color model uses position within a cube to describe colors. The axes of the cube are the red, green, and blue values. The shades of gray are found along the diagonal from the origin of the cube, where red, green, and blue values are zero and the apparent color is black, to the opposite corner, which appears white (red, green, and blue values are 100%). RGB is generally used in reference to the separated spectral bands of an image so that the red, green, and blue bands taken together create a natural color image. (See also: HBS, HIS.)
RGBB
A display method that converts an RGB raster set into an HBS raster set and then substitutes a fourth coextensive raster object for the brightness component before conversion back to RGB components for display. The object selected for the brightness component is generally of higher resolution than the objects selected for the RGB components and imparts a higher pseudo-resolution to the displayed image. (See also: HBS, RGB.)
RGBI
A display method that converts an RGB raster set into an HIS raster set and then substitutes a fourth coextensive raster object for the intensity component before conversion back to RGB components for display. The object selected for the intensity component is generally of higher resolution than the objects selected for the RGB components and imparts a higher pseudo-resolution to the displayed image. (See also: HIS, RGB.)
RGB set
A set of coregistered, coextensive rasters that represent the red, green, and blue bands of an image.
RGB video
A video image composed of separate red, green, and blue signals. RGB video is a general term that applies to different technologies (analog or digital) and standards (like TTL and RS-170).
root window
The main window of the X server. Each client process runs as a subwindow within the root window. On DOS/Windows 3.1 systems, you can choose to display the MicroImages X Server title bar if desired. Besides identifying the MicroImages X Server, this title bar provides the pixel depth of the current display mode, the screen resolution, and MicroImages' technical support number.
row
A horizontal list of data values or display cells in a raster object or display.
RS-170 video
A standard for RGB analog video in the USA that governs the form of the RGB color signals. RS-170 video has a 15.7 kHz horizontal scan rate and a 30-cycle per-second frame rate. It is not modulated with a carrier as is broadcast video.
rubbersheeting
Any process in which a raster is stretched differentially to match a new set of geometric constraints. This shape change could be defined by any one of many transformations such as changing a map projection, trilateration to change the absolute position of cells within a raster, fitting a polynomial to a surface, least squares movement of control cells, and so on.
RVC file
Raster/Vector/CAD formatted file. These files incorporate the benefits of a 32-bit compiler. (See also: project file.)
RVF file
Raster/Vector Format(ted) file. The DOS extension for all MIPS project files is .RVF. When looking for project files, MIPS searches and accesses only files with a .RVF extension. (See also: project file.)