A-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)


Accuracy
Accuracy is the closeness of results of observations, computations, or estimation of spatial features to their true value of position. “Absolute accuracy" is the differential between the actual real world location of a point on the surface of the earth and its mathematically assigned geographic coordinate.


Address Matching
Process that compares a table of addresses to the address attributes of a theme to convert textual addresses to locations on a map. Street name and address values are compared to database records to find the street segment with a matching name and address range. The address is then located at a prorata distance from the street segments start point proportional to the addresses value relative to the street's address range value and on the appropriate side of the street (even addresses always on the right, etc.). Also see the term “geocoding”.


Annotation
Annotation is text or labels plotted graphically on a map or drawing. Text or labels are used for naming such map features as streets and places; unique identification numbers assigned to individual map features including parcels, utility nodes and links; dimensioning; posted notes and instructions; descriptive text used to label area features such as soil types, zoning categories. Annotation is typically primitive map features and is not intelligently associated to the map feature and/or possible linked DBMS records.

Application
An application is the use of software, data, procedures and techniques in a series of steps that are then put into practice to solve a problem or perform a function. For example, an “abutter mailing labels” application would enable a user to identify a property, typically with its address. The application would then either enable to user to select abutting properties, or would select abutters automatically. Once the abutters were identified, the application would use information in the GIS database to produce a mailing label for each abutter. Additional capabilities might include making a map showing the target property and its abutters or performing a merge of a standard letter with each of the addresses.


Arc
An arc is a series of points that form an unclosed linear feature in a spatial database.
  1. A set of XY coordinates used to represent a linear feature or a polygon boundary. It is a continuous string of XY coordinate pairs (vertices) beginning at one location and ending at another location, having length but no area.
  2. A coverage feature class used to represent linear features and polygon boundaries. One linear feature can contain many arcs.
  3. In CAD it is a curvilinear feature defined by such location combinations as Center point, radius, and starding point.
  4. Center Point, Start and End Point Start point, end point and one point in between Others.


Attributes
  • Single element of non-graphic data assigned to a spatial feature either as an imbedded data element within the spatial database or located in a linked database record.
  • Descriptive characteristics of a feature, site or phenomenon.
  • Set or collection of data that describe the characteristics of real-world conditions.


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