Glossary
- Absolute Location
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A location that use some type of reference system to define it's position on the earth’s surface.
- Active Satellites
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Satellites that detect signals from artificially generated energy sources, then strengthens and emits the signal to its next destination.
- Additive Color Model
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A color model that combines emitted light to display color variations.
- Aggregation
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A formation of data taken, then prepared and combined for processing.
- Analytical Mapping
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A map that is easy to find patterns or trends with using data.
- Ancillary
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An item that supports another item.
- Append
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Combines the spatial extent of two or more layers to create a new output polygon.
- Arc-Node Topology
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A lined data structure that represents linear features, and polygon boundaries, to support analysis functions.
- Arcs
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Similar to the function of a line, but are curved.
- Area Definition
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An arc that connects to surround an area defining a polygon.
- Aspect Maps
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Uses slope information to produce output raster images whereby the value of each cell denotes the direction it faces.
- Balance
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Provides the visual impact of the arrangement of the map elements. There are two factors to consider related to the balance: Weight and direction.
- Boolean Raster Overlay
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Connectors AND, OR, and XOR can be employed to combine the information of two overlying input raster datasets into a single output raster.
- Buffering
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The process of creating an output polygon layer containing a zone (or zones) of a specified width around an input point, line, or polygon feature.
- Buffers
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Common vector analysis tools used to address questions of proximity in a GIS and can be used on points, lines, or polygons.
- Cartograms
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Maps that distort area or distance by substituting another thematic variable.
- Cartographic Process
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A recommended set of steps that you should follow in order to properly create a map, composed of five steps: define purpose and meaning of the map; choose the scale of the map; determine the map format, printing limitations you may have, and the economics of production and reproduction of the map; abstract and generalize the data; the design and the layout of the map.
- Cartography
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The practice of drawing maps.
- Cell-by-Cell Raster Encoding
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Encodes a raster by creating records for each cell value by row and column.
- Centroid
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The center of mass of a geometric object of uniform density.
- Choropleth Map
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A thematic map that uses tones or colors to represent spatial data as average values per unit area.
- Classification
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When you combine observations into a larger group or class to simplify the data so that it can be displayed easier on the map.
- Clip
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A method that is used to extract features from an input point, line, or polygon layer that falls within the spatial extent of the clip layer.
- Cluster Tolerance
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A feature in GIS software that forces nearby lines to be snapped together if they fall within a user-specified distance.
- CMYK
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Cyan, magenta, yellow, black; the most common subtractive color model and is occasionally referred to as a "four-color process.”
- Color Wheel
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A visual representation of colors arranged according to their chromatic relationships. Primary hues are equidistant from each other with secondary and tertiary colors intervening.
- Column
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A vertical arangement of figures or other information.
- Connectivity
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The arc-node topology for the feature dataset.
- Constant Width Buffers
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This process will require users to input a value by which features are buffered.
- Contiguity
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Polygons that share an arc are deemed adjacent. The side of each arc can be defined.
- Continuous Features
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Features that are less well defined and exist across space. The most commonly cited examples of continuous features are temperature and elevation.
- Contrast
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The state of being strikingly different from something else in juxtaposition or close association.
- Cool Colors
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Colors associated with overcast days. Cool color hues range from blue-green through blue-violet and include the majority of gray variants.
- Coordinate Systems
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Frameworks that are used to define unique positions.
- Cropped Map Body
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Represents a region of interest within a geographic context and the surrounding area is cut off often by a neat line.
- Dasymetric Map
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A thematic map that is an alternative to a choropleth map, but instead of mapping the data so that the region appears uniform, ancillary information is used to model the internal distribution of the data.
- Data Source
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Where the map data was derived from.
- Diffusion
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The spreading of something from one place to another; can relate to the physical movement of people or the spread of disease, or the diffusion of ideas, technology, or other intangible phenomena.
- Direction
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The position of something relative to something else, usually along a line.
- Directional Indicator
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Typically a North arrow. The purpose of a directional indicator is to indicate a direction on a map.
- Discrete Features
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Features that are well defined and are easy to locate, measure, and count, and their edges or boundaries are readily defined. Examples of discrete features in a city include buildings, roads, traffic signals, and parks.
- Dissolve
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Combines adjacent polygon features in a single feature dataset based on a single predetermined attribute.
- Distance
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The degree or amount of separation between locations; can be measured in nominal or absolute terms with various units.
- Dot Map
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A thematic map that uses a dot symbol to show the presence of a feature or phenomenon; relies on a visual scatter to show a spatial pattern.
- Doughnut Buffer
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A buffer that excludes the input polygon area.
- Dynamic Maps
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Changeable or interactive representations of the earth. Dynamic mapping refers more to how maps are used and delivered to the map user today (e.g., online, via mobile phone) than to the content of the map itself.
- Ecological Fallacy
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An interruption in the interpretation of statistical data.
- Erase
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Essentially the opposite of a clip. Whereas the clip tool preserves areas within an input layer, the erase tool preserves only those areas outside the extent of the analogous erase layer.
- Error Propagation
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Occurs when inaccuracies are present in the original input and overlay layers and are propagated through to the output layer.
- Figurative Maps
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A map that shows fictional locations, usually not scaled to accuracy.
- Figure Closure
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The tendency for the viewer to complete unfinished objects or objects that may be obscured by other elements.
- Figures
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Items that have “thing” qualities and are important to the map.
- Floating Map Body
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A region that is disconnected from neighboring regions.
- Frame Line
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The first feature that should be placed into the map layout. This line is essentially a bordering box that surrounds all the map elements.
- Generalization
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The process of resolving conflicts associated with too much detail, too many features, or too much information and data to map.
- Geocoding
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A process to determine the geographic coordinates of particular street addresses, zip codes, place names, and other geographic data.
- Geographic Coordinate System (GCS)
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The coordinate system that is most commonly used to define locations on the three-dimensional earth; it is based on a sphere or spheroid, and uses latitude and longitude to determine location.
- Geographic Grid System
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Parallel and meridian lines combined to form a geographic grid system that allows users to determine their exact location on the planet.
- Geographic Information Science (GIS)
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Uses computers and satellite imagery to capture, store, manipulate, analyze, manage, and present spatial data. Sometimes referred to as geographic information systems.
- Geographic Perspective
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Spatially viewing the world, as a geographer.
- Geographical Information System (GIS)
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A computer-based tool used to help people transform geographic data into geographic information.
- Geography
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The study of natural and human-constructed phenomena relative to a spatial dimension.
- Geoprocessing
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Specialized software tools used to compare, analyze, or manipulate map layers and their underlying geographic data to create new sets of data.
- Geostationary Satellites
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Satellites that circle the earth proximal to the equator once each day.
- Gerrymandering
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To achieve a result by manipulating the boundaries of an electoral constituency.
- Global Operations
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Determining basic statistical values for the raster as a whole.
- Global Positioning System (GPS)
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A satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense
- Graduated Symbol Map
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The symbols vary in size as related to the values they represent.
- Graphic Scale
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Uses a graphic element, typically a bar or line, to represent a certain distance on the map.
- Graticule
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A visual representation of a coordinate system or location scheme used on the map.
- Great Circle
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Any circle that divides the earth into a circumference of two halves.
- Grounds
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The background or supporting figures on the map.
- Heading
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A title at the top of a section.
- HSL
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Hue, saturation, lightness; based on cylindrical coordinate systems whereby the angle around the central vertical axis corresponds to the hue; the distance from the central axis corresponds to saturation, and the distance along the central axis corresponds to either saturation or lightness.
- HSV
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Hue, saturation, value; based on cylindrical coordinate systems whereby the angle around the central vertical axis corresponds to the hue; the distance from the central axis corresponds to saturation, and the distance along the central axis corresponds to either saturation or lightness.
- Hue
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The dominant wavelength or color associated with a reflecting object.
- Identity
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Also referred to as “minus”, this overlay method creates an output layer with the spatial extent of the input layer, but includes attribute information from the overlay.
- Image Maps
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Maps derived from satellite images and other photos.
- Inset Map
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Secondary map areas, each encased within their nearline; often display the primary mapped area in relation to a larger area.
- Insets
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Secondary map areas, each encased within their neat line; often display the primary mapped area in relation to a larger area.
- International Date Line
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The line determines where the new day begins in the world. It is located 180 degrees longitude from the Prime Meridian, in the Pacific Ocean.
- Interpolation
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Technique that estimates the value of all unknown points between the known points.
- Interposition
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The interrupting of the edge of one object with another object that causes the object to appear on top and closer to the viewer.
- Intersection
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This method employs the AND operator.
- Isopleth Map
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A thematic map that depicts smooth continuous phenomena such as precipitation or elevation; Also known as contour maps.
- Kerning
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A typographic effect that alters the space between adjacent letters in a word.
- Kriging
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A complex geostatistical technique that employs semivariograms to interpolate the values of an input point layer and is more akin to a regression analysis.
- Label
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A word or words used to specify a point on the map; it's purpose is to communicate attribute or ancillary information to the map user.
- Latitude
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An angular measurement north or south of the equator relative to a point found at the center of the Earth.
- Leader Line
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A line that establishes a connection between a location on a map and text.
- Leading
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The vertical distance between lines of text.
- Legend
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Provides users with information about how geographic information is represented graphically. Usually consist of a title that describes the map, as well as a clear definition of various symbols, colors, and patterns that are used on the map.
- Line-in-Polygon Overlay
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Similar to the point-in-polygon overlay, with that obvious exception that a line input layer is used instead of a point input layer.
- Line-on-Line Overlay
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An operation that requires line features for both the input and overlay layer.
- Lines
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Features composed of multiple, explicitly connected points.
- Literal Maps
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Meant to show actual places with as much accuracy as possible.
- Local Operations
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A raster output dataset where the output value at each location is a function of the value associated with that location.
- Location
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A position on the surface of the earth.
- Location Map
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A small ancillary map that is at a smaller scale than the map body.
- Longitude
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The angular measurement east and west of the Prime Meridian.
- Map
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A graphic representation of the real world.
- Map Abstraction
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The process of moving from the “real world” to the world of maps.
- Map Body
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The main focus of the map and should be visually dominant in every case; contains the features important to the message of the map.
- Map Elements
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Elements of a map may include a neat line, map body, graticule, insets, title, legend, label, ancillary text, ancillary object, scale bar, directional indicator, and metadata.
- Map Projections
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A representation of Earth’s surface on a flat plane; The methods and procedures that are used to transform the spherical three-dimensional earth into two-dimensional planar surfaces; Mathematical formulas that are used to translate latitude and longitude on the surface of the earth to x and y coordinates on a plane.
- Map Scale
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The ratio between the distance between two locations on a map and the corresponding distance on Earth’s surface.
- Map Title
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A title for the map to be called, and relates to the data being shown.
- Mapped Area
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The primary geographic component of the overall map. The mapped area contains all of the features and symbols used to represent the spatial phenomena being displayed.
- Mathematical Raster Overlay
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The numbers within the aligned cells of the input grids can undergo any user-specified mathematical transformation.
- Mental Maps
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Maps of our environment that are stored in our brains.
- Merge
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Combines features within a layer into a single feature with identical attribute information.
- Metadata
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Purpose is to cite the source of data sets used to create the map. Can contain the map author’s information, such as their name, and contact information; should also include the date the map was created and other explanatory information about the creation of the map such as the map projection used.
- Modifiable Areal Unit Problem
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Statistical bias that can significantly impact the data being shown on a map.
- Multiple Ring Buffers
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A buffer field that changes width.
- Navigation
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How we move through the environments where we live, work, and play; destination-oriented travel.
- Neat Lines
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Border boxes that are placed around individual map elements; must occur within the frame line.
- Neighborhood Operations
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Neighborhood operations examine the relationship of an object with similar surrounding objects.
- Node
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A common coordinate pair between intersecting lines or polygons.
- Nominal Location
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A location simply defined and described by name.
- North Arrow
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An arrow on a map telling the reader which way is north.
- Opisometer
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A device uses a small rotating wheel that records the distance traveled.
- Orientation
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The relationship between the directions on the map and the corresponding compass directions in reality.
- Orthophotos
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A vertical photographs that have been geometrically “corrected” to remove the curvature and terrain-induced error from images.
- Overall Map
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A map of small scale used for general planning purposes.
- Overlay
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To lie on top of another.
- Parallels
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Lines connecting points of the same latitude.
- Passive Satellites
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Reflects the signal from one earth station to other earth station(or stations) without any amplification or retransmission.
- Perceptual Grouping
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In a perceptual group the viewer spontaneously combines elements that share similar properties; elements can be grouped by shape or by size.
- Pictogram
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A pictorial symbol for a word or a phrase.
- Point-in-Polygon Overlay
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This operation requires a point input layer and a polygon overlay layer. A new output point layer is returned that includes all the points that occur within the spatial extent of the overlay.
- Points
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Zero-dimensional objects that contain only a single coordinate pair.
- Polygon Topology
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It is the spatial relationships between adjacent or contiguous features.
- Polygon-Arc Topology
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A model that stores geographic representations (a series of lines that enclose an area, forming a polygon) as one of its properties.
- Polygon-in-Polygon Overlay
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This operation employs a polygon input and a polygon overlay.
- Polygon-on-Line Overlay
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The opposite of the line-in-polygon operation. In this case, the polygon layer is the input, while the line layer is the overlay.
- Polygon-on-Point
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the polygon layer is the input, while the point layer is the overlay.
- Polygons
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Shapes created by multiple lines that loop back to create a “closed” feature.
- Positive Spatial Autocorrelation
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Nearby values of a variable that tend to be similar.
- Prime Meridian
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A line of longitude that has a value of zero degrees.
- Projection
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A way to flatten a globe's surface into a plane in order to make a map.
- Proportional Symbol Map
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A thematic map that uses symbols of different sizes to represent data associated with different areas or locations within the map.
- Proportional Symbols
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Symbols for a single, quantitative variable that are sized proportionally to match the data values.
- Quad-Tree Raster Encoding
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This method divides a raster into a hierarchy of quadrants that are subdivided based on similarly valued pixels.
- Radiometric Resolution
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Refers to the sensitivity of the sensor to variations in brightness and specifically denotes the number of grayscale levels that can be imaged by the sensor.
- Range Graded Symbols
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Group raw data into classes with each class represented by a differently sized symbol.
- Raw Data
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Data that has not been used or processed.
- Reference Map
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A map that delivers location information to the map user.
- Relational Raster Overlay
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This method utilizes relational operators to evaluate conditions of the input raster datasets.
- Relative Location
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Location by defining and describing places in relation to other known locations.
- Remote Sensing
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The process of gathering data about an area by remotely sensing electromagnetic radiation reflected and emitted from Earth’s surface.
- Representative Fraction Scale
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Two numbers are written separated by a colon. The number of the left of the colon represents the distance measurement map and a number to the right of the colon represents distance measured on the ground.
- RGB
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Red, green, blue; The RGB color model combines light beams of the primary hues of red, green, and blue to yield additive secondary hues of magenta, cyan, and yellow.
- Run-Length Raster Encoding
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This method encodes cell values in runs of similarly valued pixels and can result in a highly compressed image file.
- Saturation
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The intensity of color. Full saturation results in pure colors, while low saturation colors approach gray — variations in saturation yield different shades and tints.
- Scale
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The ratio between the distance between two locations on a map and the corresponding distance on Earth’s surface.
- Scale Bar
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A bar representing a certain distance on the map; often divided at meaningful intervals to assist the map reader in measuring.
- Select
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An output layer based on the selection of a particular feature(s) from the input layer.
- Selection
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When you choose a subset of data that you wish to display on the map.
- Serif
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A slight projection finishing off a stroke of a letter in certain typefaces.
- Setback Buffers
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Buffer that includes ONLY the input polygon area.
- Shades
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Produced by blocking light, such as by an umbrella, tree, curtain, and so forth. Increasing the amount of shading results in grays and blacks.
- Simplification
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Simplifying complex geometric detail so that it looks smoother and appropriate for the scale which you are mapping.
- Slivers
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A common error produced when two slightly misaligned vector layers are overlain.
- Slope Maps
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Are made to assess watershed units, inventory forest resources, determine habitat suitability, estimate slope erosion potential, and so forth.
- Small Circles
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Circles that cut the earth, but not into equal halves.
- Space
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A somewhat ambiguous and generic term that is used to denote the general geographic area of interest.
- Spaghetti Data Model
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A model in which each point is represented as a string of coordinate pairs with no inherent structure.
- Spatial Join
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A hybrid between an attribute operation and a vector overlay operation. It results in the combination of two feature dataset tables by a common attribute field.
- Spatial Resolution
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The number of pixels utilized in construction of a digital image.
- Spectral Resolution
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Denotes the ability of the sensor to resolve wavelength intervals, also called bands, within the electromagnetic spectrum.
- Spheroid
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A spherical, round or circle like shape.
- Split
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An operation that is used to divide an input layer into two or more layers based on a split layer.
- Standardization
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The process of making data uniform, or generalized.
- Strong Edges
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Thick drawn edges that help define an object as a figure.
- Subtractive Color Model
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Involves the mixing of paints, dyes, or inks to create full-color ranges. Subtractive models display color on the assumption that white, ambient light is being scattered, absorbed, and reflected from the page by the printing inks.
- Sun-Synchronous Satellites
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A satellite that can synchronize to a near-polar orbit of the sensor with the sun’s illumination.
- Surface
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Dataset that contains an attribute value for every locale throughout its extent.
- Symbolization
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To use representative shapes, icons, or pictures to represent items or spatial phenomena.
- Symmetrical Difference
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Employs the XOR operator, which results in the opposite output as an intersection.
- Target Cell
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Cell found in the center of the 3-by-3 moving window.
- Temporal Resolution
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The amount of time between each image collection period and is determined by the repeat cycle of the satellite’s orbit.
- Terrain (Elevation) Analysis
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When information is calculated on raster surfaces such as DEMs.
- Texture
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The compactness of the marks that make up the symbol; also referred to as spacing.
- Thematic Maps
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Maps concerned with a particular theme or topic of interest, and how things are distributed across space.
- Time Zone
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A zone where time is measured relative the Coordinated Universal Time (UTC) standard at the Prime Meridian.
- Tint
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The opposite of shade and is produced by adding white to a color.
- Title
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The name of a map.
- Topological Data Model
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A model that is characterized by the inclusion of topological information within the dataset.
- Topology
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Rules that model the relationships between neighboring points or polygons, and determines how they share geometry.
- Toponymy
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The study of place names and their respective history and meanings.
- Union
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Preserves all features, attribute information, and spatial extents from both input layers.
- Value
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The amount of white or black and is often synonymous with contrast.
- Variable Width Buffers
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A premade buffer field within the attribute table to determine the buffer width for each specific feature in the dataset.
- Vector Data Models
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A display of data using points, lines, curves, and polygons.
- Verbal Scale
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A sentence that describes the relationship of the distance on the ground to the distance on the map.
- Vertex
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Each bend along a line or polygon that is not the point of intersect.
- Viewshed Analysis
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Technique that uses the elevation value of cells in a DEM or TIN to determine those areas that can be seen from one or more specific location.
- Visual Hierarchy
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The intellectual plan for the map and the eventual graphic solution that satisfies the plan.
- Warm Colors
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Colors associated with a bright, sunny day. Warm colors are typified by hues ranging from red to yellow, including browns and tans.
- Water
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Gives the reader geographic references to help recognize landmasses.
- Watershed Analyses
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A series of surface analysis techniques that define the topographic divides that drain surface water for stream networks.
- Web GIS
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The integration of the vast amounts of content available on the Internet (e.g., text, photographs, video, and music) with geographic information, such as location.
- Winkel Tripel Projection
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So-named because its creator, Oswald Winkel, sought to minimize three kinds of distortion: area, direction, and distance. The National Geographic Society has used it since 1998 as the standard projection of world maps.
- Zonations
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Distribution in zones or regions, such as zip-codes and area codes for phone numbers.