GIS — page 5 of 6

GIS terms

401. Police Service Area (PSA) Every resident lives in a Police Service Area, and every PSA has a team of police officers and officials assigned to it.
402. polygon A coverage feature class used to represent areas. A polygon is defined by the arcs that make up its boundary and a point inside its boundary for…
403. polygon overlay A topological overlay procedure which determines the spatial coincidence of two sets of polygon features and creates a new set of polygons based on…
404. polygon-arc topology The topological data structure ARC/INFO uses to represent connectivity between arcs to form polygons.
405. POSIX 1003.1A A revision to the POSIX 1003.1 standard that defines a set of standard operating system interfaces and an environment for application programs written in…
406. POSIX 1003.4a Defines thread support to facilitate writing multitasking operations, particularly server applications.
407. POSIX character set POSIX character sets support languages which only require 7-bit characters (such as US English). See also extended character set.
408. PostScript PostScript is a page-description computer language developed, marketed, and trademarked by Adobe Systems, Inc.
409. Precinct See County Election Precinct and Election Day precinct.
410. Precision The accuracy with which a number can be represented, i.e., the number of digits used to represent a number.
411. preliminary topology Refers to incomplete region topology. Region topology defines region-arc and region-polygon relationships.
412. primary key One or more attributes whose values uniquely identify a row in a database table. See also foreign key.
413. Production The process of delivering to another party, or making available for that partys review, documents deemed responsive to a discovery request.
414. profile A sectional view showing grades and distances, usually taken along the centerline.
415. projection See map projection.
416. projection file A coverage file that stores the parameters for the map projection and coordinate system of a geographic data set (e.g., a coverage).
417. Property and Land For example, resources describing cadastral surveys and land ownership.
418. proximal tolerance The minimum distance in ground units separating all point locations on the horizontal plane.
419. pseudo node A node where two, and only two, arcs intersect, or a single arc that connects with itself.
420. Public Safety Resources related to emergency services. For example, Fire, EMS, and Police.
421. Public Services Resources related to social and governmental services provided to the public.
422. quadrangle (quad) See topographic map.
423. QUADRANT The District of Columbia is divided into four quadrants: Northwest, Northeast, Southwest and Southeast.
424. quadtree A spatial index which recursively decomposes a data set (e.g., image) into square cells of different sizes until each cell has a homogeneous value.
425. quarter quad One-quarter area of a four-sided quadrangle that depicts 7.5 minutes of latitude and 7.5 minutes of longitude on a side.
426. Query A request for identification of a set of assets, expressed in terms of a set of criteria, which the identified item must satisfy.
427. raster A cellular data structure composed of rows and columns for storing images. Groups of cells with the same value represent features. See also grid.
428. real numbers Decimal numbers (e.g., 3.1417, 0.25, 1.8992, 6.0).
429. record All the documents and evidence plus transcripts of oral proceedings in a case.
430. Record Lot Defined by the DC Surveyor. These are official, platted, recorded subdivision lots created by the DC Surveyor's Office in compliance with the Subdivision…
431. Recreation Recreational opportunities at more than 1,900 federal recreation sites managed by the Bureau of Reclamation and other federal agencies can be found at the…
432. rectification The process by which an image or grid is converted from image coordinates to real-world coordinates.
433. referential integrity The capability to ensure that changes to one table that affect other tables are transmitted to those other tables.
434. region A coverage feature class used to represent a spatial feature as one or more polygons. Many regions can be defined in a single coverage.
435. registered table A DBMS table which is part of an ArcStorm database is said to be 'registered' with the database.
436. relate An operation that establishes a temporary connection between corresponding records in two tables using an item common to both (i.e., relate key).
437. relate key The common set of columns used to relate two attribute tables. See also relate, primary key and foreign key.
438. relation See table.
439. relational database A method of structuring data as collections of tables that are logically associated to each other by shared attributes.
440. Relational database management system (RDBMS) (RDBMS) 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 (item).
441. relational join The operation of relating and physically merging two attribute tables using their common item.
442. Remote Procedure Call (RPC) (RPC) A Remote Procedure Call (RPC) is a communication mechanism which allows one UNIX process to communicate with another UNIX process.
443. remote sensing Method for determining characteristics of an object, organism or community from afar.
444. resampling The process of reducing image data set size by representing a group of pixels with a single pixel.
445. Reservations Lands acquired for use by the Federal Government after the original founding of the city. There are presently more than 750 US Reservations in DC.
446. Resolution See DPI.
447. Restore To transfer data from a backup medium (such as tapes) to an on-line system, often for the purpose of recovery from a problem, failure, or disaster.
448. ridgeline A line representing the intersection or top between opposite slopes. Commonly used as a parcel line.
449. roll back To cancel any changes to a database made during the current transaction. Compare with commit.
450. Root mean square (RMS) error (RMS) A measure calculated when registering a map to a digitizer, indicating the discrepancy between known point locations and their digitized locations.
451. route A route of administration is a way of administering a drug to a site in a patient.
452. route attribute table (RAT) (RAT) Route attribute table. An RAT stores route attributes. There is one RAT for each route-system in a coverage.
453. route measure A location along a route, defined as a measure from a start point, where measures include distance, time, milepost, address range.
454. route-system A collection of routes representing separate instances of a common linear entity, for example, all school bus routes in a city.
455. ROW Rest-of-World.
456. rubber sheeting A procedure to adjust coverage features in a nonuniform manner. Links representing from- and to-locations are used to define the adjustment.
457. run-length encoding A data compression technique for storing raster or gridded data. Run-length encoding stores data by row.
458. satellite image A picture of the earth taken from an earth-orbital satellite. Satellite images may be produced photographically or by on-board scanners (e.g., MSS).
459. satellite imagery Imagery that is collected using a space-borne remote system that is in orbit around the Earth.
460. Scale Ratio of map distance to Earth distance. Thus, in a 1:24,000 scale map, one centimeter, inch, or foot equals 24,000 centimeters, inches, or feet on the…
461. scale bar A map element that shows the map scale graphically.
462. Scanning Scanning is the process of converting a hard copy paper document into a digital image for use in a computer system.
463. scratch file A temporary file holding intermediate data during an operation, such as when calculating arc intersections, or building feature topology.
464. section An area equal to 640 acres or 1 square mile.
465. section line A line on a surface defining the position of a profile.
466. Section table (SEC) (SEC) Section table for the section feature class in a coverage. The SEC holds attributes about sections.
467. selection coverage A coverage whose area overlaps that of a map library. It identifies the area to extract data from, or insert data into, a map library.
468. Selective Availability (S/A) (S/A) A U.S. Department of Defense program to limit the accuracy of autonomous position fixes computed by civilian receivers.
469. setuid A process which can set its effective user to super-user (root). That is, although any user can run the process, the process can then execute operations…
470. shade symbol A pattern used to shade polygons in ARC/INFO. Shade symbol patterns include crosshatch, repeating, and solid fill.
471. Single Member District (SMD) (SMD) Single Member Districts are boundaries, within ANCs, developed by the DC City Council.
472. single precision Refers to a level of coordinate accuracy based on the number of significant digits that can be stored for each coordinate.
473. sliver polygon A small areal feature commonly occurring along the borders of polygons following the topological overlay of two or more coverages.
474. slope An inclined surface usually defined by the ratio of the horizontal distance to the vertical distance, i.e. 2:1 (2 horizontal units to 1 vertical unit).
475. snapping The process of moving a feature to coincide exactly with coordinates of another feature within a specified snapping distance, or tolerance.
476. soundex A phonetic spelling (up to six characters) of a street name, used for address matching.
477. spatial analysis The process of modeling, examining, and interpreting model results. Spatial analysis is useful for evaluating suitability and capability, for estimating…
478. spatial data Information about the location and shape of, and relationships among, geographic features, usually stored as coordinates and topology.
479. Spatial Data Transfer Standard/Topological Vector Profile (SDTS/TVP) (SDTS/TVP) A United States Federal standard designed to support the transfer of different types of geographic and cartographic spatial data.
480. spatial feature See geographic feature.
481. spatial indexing A means of accelerating coverage drawing, spatial selection, and feature identification by generating feature-based indexes for one or more feature…
482. spatial interaction An analytical technique that estimates the number of interactions occurring between an origin and destination locations.
483. spatial modeling Analytical procedures applied with a GIS. There are three categories of spatial modeling functions that can be applied to geographic features within a…
484. spatial order An index assigned to features based on their relative closeness in two-dimensional space.
485. spatial query See map query.
486. spike 1. An inflorescence in which the main axis is elongated and the flowers are sessile. 2.
487. spline A mathematical curve used to smoothly represent spatial variation. A spline operation inserts vertices to create a curve in an arc.
488. SQL/MM An international standards effort, sponsored by ISO to extend SQL to support multimedia applications, including access and manipulation of geographic data.
489. Square A unit of land defined by the DC Surveyor that normally consists of a single city block and contains record and tax lots.
490. SSD OBSOLETE. Space Systems Division. (Now USAF/SMC.)
491. SSL See definition for: Secure Sockets Layer (SSL)
492. Standard interchange format (SIF) (SIF) a spatial data exchange format. A standard or neutral format used to move graphics files between computer systems.
493. Standardized raster graphic (SRG) (SRG) a digital representation of a map or chart, which is captured by automatic digitization (scanning), stored on a digital storage media, and displayed on a…
494. State Plane Coordinates (SPC) (SPC) A map projection that measures distance in feet. By providing an SPC easting (x) and northing (y), the state name, and the zone number, any location in…
495. station file An AML file containing commands needed to establish the environment for graphic display and graphic input.
496. Status The legal standing of a patent appplication or patent. MPEP 102.
497. stop Stops are locations visited in a path or tour; they may represent customers on a delivery route or cities in a highway system.
498. stop impedance The time it takes for a stop transfer to occur. This is used to compute the impedance of a path or tour.
499. stop transfer The number of things or packages transferred at a stop. This is used to find the total number of transfers on a path or tour.
500. street centerline A real or imaginary line that is equidistant from the sides (usually pavement edges) of a travel path.