R-GIS Glossary,

Posted on Jul 2, 2007 By : Mizake Laziaf
This glossary is a sub-set of one developed by the Urban and Regional Information
Systems Association (URISA)


Raster
  • Images containing individual dots with color values, called cells (or pixels), arranged in a rectangular, evenly spaced array. Aerial photographs and satellite images are examples of raster images used in mapping. When maps or other documents are scanned, the result is also a raster.
  • Method for storing spatial data that involves assigning a value to each dot in a large matrix. This method is very useful for modeling continuous phenomena like elevation of temperature.


Record
  • An assemblage of textural data within a DBMS table and/or drawn statement as a means of preserving knowledge.
  • Collected and preserved data describing a particular subject.
  • A row (series of field values) in a database table. In a spatial database, each graphic feature may be linked to one or more records in one or more tables.
  • A collection of fields or other sub-portion of computer file treated as a data unit.


Rectification
Rectification is a set of techniques for removing data errors though calculation or adjustment. In image processing, computer programs that remove distortion within a digital image, aerial photography or remotely sensed data by removing parallax errors due to relief (high ground being closer to the camera than low lying areas), camera tilt, corner and other distortions.


Relate
Relate means to establish or demonstrate a connection between two or more things. In spatial analysis, establishing a temporary connection between records in two different tables using an item common to both. For example, a property identifier on a map can be used to relate the property to information in an assessing database because the same identifier appears in the assessor’s database.

Relational Database
This phrase refers to an information storage system in which there is an association between two or more things organized according to relationships between data items. A relational database is a collection of tables that are logically associated to each other by shared common attributes. Entering the table name, attribute name, and the value of the primary key, any data element or set of elements can be retrieved. A relational database consists of table rows and columns. Also see DBMS.

Remote Sensing
Using a recording device not in physical contact with the surface being analyzed including:
  1. Using sensors sensitive to various bands of the electromagnetic spectrum.
  2. Assessing its spectral image without having the sensor in direct contact with the surface.
  3. Interpreting environmental conditions at, below and above the surface of the earth, typically by processing images from an aircraft (i.e. aerial photography), satellite imaging (ie. SPOT), or radar.

Resolution
Fineness of detail that can be distinguished in an image, as on a video display terminal.
  1. "Display Resolution" The density of the pixels that compose an image (See Pixels). The greater the number of pixels per square inch of screen, the greater the resolution. In print, resolution is measured in dots per inch (dpi).
  2. "Spatial Resolution" The smallest possible map feature that can be accurately displayed at a specified map scale. For example, in a 1:24000 scale map, a 50 foot distance between a roadway and railroad track centerline is one fortieth of an inch. Since the thinnest pen line width is presumed to be one fortieth of an inch, it is impossible to accurately represent the alignment of these two centerlines and still have a visible gap between them. To do this takes a smaller map scale (<>


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