Geospatial and Drone Common Terms


Private domain complete GIS software package from ESRI, Inc. that has very powerful modeling, analysis and output capabilities


Altitude is specified relative to either mean sea level (MSL) or an ellipsoid (HAE). Altitude above an ellipsoid is the distance from a precise mathematical model, whereas altitude above Mean Sea Level is a distance from a surface of gravitational equipotential that approximates the statistical average level of the sea.


1. Descriptive text used to label coverage features. It is used for display, not for analysis.
2. One of the feature classes in a coverage used to label other features. lnformation stored for annotation includes a text string, the location at which it is displayed, and a text symbol (color, font, size, etc.) for display.


1. An ordered string of vertices (x,y coordinate pairs) that begin at one location and end at another. Connecting the arc's vertices creates a line. The vertices at each endpoint of an arc are called nodes.
2. A coverage feature class used to represent linear features and polygon boundaries. One line feature can contain many arcs. Arcs are topologically linked to nodes (arc-node topology) and to polygons (polygon-arc topology).


File and data management module of ArcGIS. Can be used to create and manage metadata.


A comprehensive desktop GIS software package developed by ESRI.


Editing and map making module of ArcGIS


Spatial database engine. This is a middleware that facilitates transactions between ArcGIS and a DBMS. This allows multi-users and simultaneous editing.


Data management and analysis module of ArcGIS. Contains geoprocessing tools.


Private domain GIS software from ESRI, Inc. that allows users to organize, maintain, visualize, and disseminate maps and spatial information. This GIS software does not have the analysis and modeling capabilities of ARC/lNFO.


A preserved collection of historical data or information.

Area of Interest (AOI)

1. A homogeneous extent of the Earth bounded by one or more arc features (polygon) or represented as a set of polygons (region). Examples: states, counties, lakes, land-use areas, and census tracts.
2. The size of a geographic feature measured in unit squares.


The compass direction toward which a slope faces, measured in degrees from North in a clockwise direction.


A characteristic of a geographic feature, typically stored in tabular format and linked to the feature in a relational database. The attributes of a well-represented point might include an identification number, address, and type.

Attribute Table

A tabular file containing rows and columns. In a GIS, attribute tables are associated with a class of geographic features, such as wells or roads. Each row represents a geographic feature. Each column represents one attribute of a feature, with the same column representing the same attribute in each row.


The horizontal direction of a vector, measured clockwise in degrees of rotation from the positive y-axis, for example, degrees on a compass.


Generic term used to refer to a type of base layer, especially as a reference for onscreen digitizing in GIS.


One layer of a multispectral image representing data values for a specific range of the electromagnetic spectrum of reflected light or heat (e.g., ultraviolet, blue, green, red, near- infrared, infrared, thermal, radar, etc.). Also, other user-specified values derived by manipulation of original image bands. A standard color display of a multispectral image shows three bands, one each for red, green and blue. Satellite imagery such as LANDSAT TM and SPOT provide multispectral images of the Earth, some containing seven or more bands.

Base Layer

A primary layer for spatial reference, upon which other layers are built. Examples of a base layer typically used are either the parcels, or street centerlines.

Base Map (or Base Layer)

A map containing geographic features that is used for reference. Roads, for example, are commonly found on base maps.


6-digit hydrologic unit delineated for the nation by USGS. Commonly used as a clip boundary.


A direction from your current position to some other point of interest. Bearings are measured in degrees (360 in a full circle), clockwise from either true or magnetic North. See also heading.

Boolean Expression

A type of expression that reduces to a true or false (logical) condition. A Boolean expression contains logical expressions (e.g., DEPTH > 100) and Boolean operators. A Boolean operator is a keyword that specifies how to combine simple logical expressions into complex expressions. Boolean operators negate a predicate (NOT), specify a combination of predicates (AND), or specify a list of alternative predicates (OR). For example, DEPTH > 100 AND DIAMETER > 20


A zone of a specified distance around a feature


Common land unit. A vector outline of tracts and/or fields. Many CLU polygons make up a coverage. The definition adopted for use in USDA service centers is: “The smallest unit which has a permanent, contiguous boundary, common management or treatment, common owner, or common client association." An example of a CLU might be a CRP field, a fenced pasture, or a strip in a crop/fallow rotatio


The Content Standards for Spatial Metadata. A document produced by the Federal Geographic Data Committee (FGDC) that describes spatial metadat

Cartesian Coordinate System

A two-dimensional, planar coordinate system in which x measures horizontal distance and y measures vertical distance. Each point on the plane is defined by an x,y coordinate. Relative measures of distance, area, and direction are constant throughout the Cartesian coordinate plane.

Central Meridian

A zone constant used when defining a map projection.


The vertical dimension of a table. A column has a name and a data type applied to all values in the column.


A software tool used to reduce the size of large raster files. Compression can be lossless, which preserves image quality, or lossy, which sacrifices some image quality for the sake of greatly reduced file size. Examples include MrSID and JPEG2000.


1. A specific set of satellites used in calculating positions; 3 satellites for 2D fixes, 4 satellites or more for 3D fixes.
2. All of the satellites visible to a GPS receiver at one time. The optimum constellation is the constellation with the lowest PDOP.


A line connecting points of equal surface value.

Contour Interval

The difference in surface values between contours.


An x,y location in a Cartesian coordinate system or an x,y,z coordinate in a three dimensional system. Coordinates represent locations on the Earth’s surface relative to other locations.

Coordinate System

A reference system used to measure horizontal and vertical distances on a planimetric map. A coordinate system is usually defined by a map projection, a spheroid of reference, a datum, one or more standard parallels, a central meridian, and possible shifts in the x- and y-directions to locate x,y positions of point, line, and area features. A common coordinate system is used to spatially register geographic data for the same area.


1. A digital version of a map forming the basic unit of vector data storage in ARC/INFO. A coverage stores geographic features as primary features (such as arcs, nodes, polygons, and label points) and secondary features (such as tics, map extent, links, and annotation). Associated feature attribute tables describe and store attributes of the geographic features.

2. A set of thematically associated data considered as a unit. A coverage usually represents a single theme such as soils, streams, roads, or land use.

Coverage Extent

The coordinates defining the minimum bounding rectangle (i.e., xmin,ymin and xmax,ymax) of a coverage or grid. All coordinates for the coverage or grid fall within this boundary.


Digital Geospatial Metadata. DGM was approved in June 1994 by the Federal Geographic Data Committee (FGDC). DGM describes the specifications for the content, quality, condition, and other characteristics of metadata (data about data). The standard provides a common set of terminology and definitions for the documentation of geospatial data. DGM establishes the names of data elements and groups of data elements to be used for these purposes, definitions of these data elements and groups, and information about the values that are to be provided for the data elements


1. Digital line graph files from the U.S. Geological Survey (USGS), including data from the base map categories such as transportation, hydrography, contours, and public land survey boundaries.
2. The digital format standards published by USGS for exchanging cartographic data files and in which the USGS delivers digital line graph data sets.


Digital orthophoto quadrangle. Digital representation of an aerial photograph or other remotely sensed data that have been rectified to produce an accurate image of the earth by removing tilt and relief displacements which occurred when the photo was taken. Standard USGS format is one quarter of a 7.5' quad. Data is provided at the 1:12000 scale. The DOQ combines the image characteristics of a photograph with the accuracy and scale associated with a map. Typical base layer required for GIS functionality.


Digital Orthophoto Quarter Quad. USGS provides DOQ data in quarter quad format for ease of use and to minimize storage requirements. Four DOQQs may be joined to form a full-quad DOQ.


Digital Raster Graphic. Scanned 1:24,000 scale USGS topographic quad. Can be used as a backdrop and to manually measure distance and obtain location coordinates, but cannot be spatially manipulated.



Digital surface model.


Digital terrain model.


Data Exchange Format. A format for storing vector data in ASCII or binary files. Used by AutoCAD and other CAD software for data interchange. DXF files can be converted to GIS coverages.

Data Conversion

The translation of data from one format to another. GIS software supports data conversion from many geographic data formats such as DLG, TIGER, DXF, and DEM.

Data Dictionary

1. (GIS) A catalog of all data held in a database, or a list of items giving data names and structures. Also referred to as DDID for data dictionary/directory.
2. (GPS) A description of the features and attributes relevant to a particular project or job. This description includes feature names, data type classifications (point, line, area), attribute names, attribute types and attribute values. After being created, a data dictionary can be used to control the capture of features and attributes.

Data Type

The characteristic of columns and variables that defines what types of data values they can store. Examples include character, floating point and integer.


A named collection of logically related data items arranged in a prescribed manner.


A set of parameters and control points used to accurately define the three-dimensional shape of the Earth (e.g., as a spheroid). The datum is the basis for a planar coordinate system. For example, the North American Datum for 1983 (NAD83) is a common datum for map projections and coordinates within the United States and throughout North America.

Digital Elevation Model (DEM)

Terrain elevation data provided in digital form.


To encode map features as x,y coordinates in digital form. Lines are traced to define their shapes. This can

be accomplished either manually or by use of a scanner.


The process of removing boundaries between adjacent polygons that have the same values for a specified attribute.


Earth Observation Satellite. An effort to study the earth as a system while tracking long-term changes on a global scale. EOS, a mission of the National Aeronautics and Space Administration (NASA), will produce petabytes (1,000 terabytes) of satellite image data and also large-scale data sets (terabytes [1,000 gigabytes] a day) to be manipulated and analyzed.

Edge Matching

An editing procedure to ensure that all features that cross adjacent map sheets have the same edge locations. Links are used when matching features in adjacent coverages.


In geometric terms, a closed surface of which all planar sections are ellipses. In GIS and mapping practices, an ellipsoid is a specific mathematical representation of the earth that more closely approximates the shape of the surface than a sphere does.


A collection of objects (persons, places, things) described by the same attributes. Entities are identified during the conceptual design phase of database and application design.


The parallel of reference 0 North or South.


Federal Aviation Administration 


The Federal Information Processing Standards. FlPS deals with a wide range of computer system components including the components of most GISs: hardware, storage media, data files, codes, interfaces, data transmission, networking, data management, documentation, programming languages, software engineering, performance, security, and so forth. FlPS 173 is the precursor to the SDTS (Spatial Data Transfer Standard), which includes standardized definitions for a variety of digital mapping terms and addresses federal requirements for accuracy. FlPS provides a U. S. government standard state and country identification code; standards approved for use by U.S. government agencies. FlPS 152-2 includes POSIX.lcompliance.


Flying First Person View (FPV) makes use of an onboard camera that relays live video to goggles, mobile phone or tablet screen.


In a GIS, a physical object or location of an event. Features can be points (a tree or a traffic accident), lines (a road or river), or areas (a forest or a parking lot).

Feature Attribute Table

A table used to store attribute information for a specific coverage feature class.


The pattern into which data are systematically arranged for use on a computer. A file format is the specific design of how information is organized in the file. DLG, DEM, and TIGER are geographic data sets with different file formats.


Geographical Resources Analysis Support System. A public domain image processing and geographic information system (GIS) originally developed by the US Army Corps of Engineers. Software upgrades are currently in development at Baylor University.


The ellipsoid used by the WGS-84 and NAD-83 datums. The best worldwide fit to the geoid.

GeoSpatial Database

A logical collection of interrelated information, managed and stored as a unit. A GIS database includes data about the spatial location and shape of geographic features recorded as points, lines, and polygons as well as their attributes.


The process of identifying a location by one or more attributes from a base layer.


The process of identifying the coordinates of a location given its address. For example, an address can be matched against a TIGER street network to determine the location of a home. Also referred to as address geocoding.


An object-based GIS data model developed by ESRI for ArcGIS that stores each feature as rows in a table. Personal geodatabases store data in a Microsoft Access .mdb file. Corporate geodatabases store data in a DBMS such as SQLserver or Oracle. This data structure supports rules-based topology and allows the user to assign behavior to data.

Geodetic Datum

A mathematical model designed to fit part or all of the geoid (the physical earth's surface). Defined by the relationship between an ellipsoid and a point on the topographic surface established as the orgin of a datum. World geodetic datums are typically defined by the size and shape of the ellipsoid and the location of the center of the ellipsoid with respect to the center of the earth.

Geographic Information System (GIS)

An organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information.