GIS TERMS AND CONCEPTS

ArcGIS

Definition: ArcGIS is a comprehensive and scalable geographic information system (GIS) software platform developed and maintained by Esri, a leading company in the geospatial industry. It is a family of integrated products and services that cater to a wide range of GIS needs, from desktop mapping and analysis to enterprise-level spatial data management and web-based mapping solutions.

Details: The ArcGIS platform allows users to create, analyze, visualize, manage, and share geographic information and spatial data. ArcGIS encompasses various components, including ArcGIS Desktop (which includes ArcMap and ArcGIS Pro), ArcGIS Server, and ArcGIS Online.

ArcGIS Online

Definition:ArcGIS Online is a cloud-based platform by Esri that allows users to create, share, and manage maps, apps, and data. It serves as a comprehensive geographic information system (GIS) that enables organizations and individuals to leverage location intelligence for better decision-making. With ArcGIS Online, users can access ready-to-use basemaps and imagery, perform spatial analysis, create interactive web maps and apps, and collaborate with others. It provides a powerful yet user-friendly environment for visualizing, analyzing, and sharing geographic information across desktop, web, and mobile devices. ArcGIS Online is a versatile platform that caters to a wide range of industries and applications, including urban planning, natural resource management, public safety, and business intelligence, among many others.

TLCGIS uses AGO to host layers, applications, and galleries for public and internal consumption and to provide end user licensing.

Details: It enables users to create maps, analyze data, collaborate, and share content. ArcGIS Online hosts maps, apps, and data in a secure infrastructure accessible from anywhere.

ArcGIS Pro

Definition: ArcGIS Pro is a powerful and modern desktop geographic information system (GIS) application developed by Esri as part of the ArcGIS platform. It is designed to be a comprehensive and intuitive solution for professional GIS users, combining advanced spatial data management, analysis, and visualization capabilities into a single integrated environment.

Details: ArcGIS Pro offers a wide range of features and functionalities that cater to the needs of GIS professionals across various industries and disciplines. It allows users to explore, visualize, analyze, edit, and manage spatial data with ease. Key features of ArcGIS Pro include: 2D and 3D mapping, geoprocessing, and integration with ArcGIS Online and ArcGIS Enterprise.

ArcMap

Definition: ArcMap is a longstanding and widely adopted desktop geographic information system (GIS) application developed by Esri as part of the ArcGIS suite. It has been a staple in the GIS industry for many years, providing a comprehensive and user-friendly environment for working with spatial data and creating high-quality maps.

Details: ArcMap offers a rich set of tools and functionalities that enable users to effectively explore, visualize, analyze, and present geographic information.

Please Note: ArcMap is set to retire in March 2026

Basemap

Definition: Basemaps serve as foundational reference maps that provide critical context for visualizing and analyzing geographic information. These basemaps are composed of diverse components including feature layers showing boundaries and landmarks, raster imagery providing land cover details, and web map tile services delivering up-to-date maps.

When creating a map, selecting an appropriate basemap is an important first step. The basemap situates the location and provides landscape patterns and features that aid in map reading. Effective basemaps should be visually appealing while remaining unobtrusive, so as not to detract from operational layers containing your key data.

Popular ESRI basemaps utilize data sources including satellite and aerial imagery, OpenStreetMap vector layers, and ESRI curated world datasets. Basemap styles range from light reference backgrounds like the Canvas basemaps, to rich terrain representations like World Imagery. ESRI offers global basemaps as well as specialized collections for individual countries and regions.

In summary, thoughtfully selecting a basemap establishes critical geographic context, enabling users to visualize, interpret, and analyze operational data layers most effectively. ESRI's diverse basemap gallery provides versatile options to meet various mapping needs. The appropriate basemap choice sets the stage for impactful location intelligence and geographic insights.

Visit the TLCGIS Basemap Gallery

Contours

Definition: In the context of GIS, contours are lines that connect points of equal elevation on a map. They are used to represent the surface of the Earth as it appears in a relief map.

Details: Contour lines help visualize the topography of an area, showing how the land rises and falls. By analyzing contours, geographers and planners can understand the terrain, identify potential areas for construction, and plan infrastructure projects.

Coordinate System

Definition: In the context of Geographic Information Systems (GIS), a coordinate system is a reference framework used to represent and communicate the precise location of geographic features or spatial data on the Earth's surface or within a specific map projection. Coordinate systems define how the coordinates (typically latitude, longitude, and optional height/depth values) are assigned to points on the Earth or within a projected coordinate space.

GIS Coordinate Systems: GIS software supports various types of coordinate systems, including:

Geographic Coordinate System (GCS): A spherical or ellipsoidal coordinate system that uses angular measurements of latitude and longitude to specify locations on the Earth's surface. Common examples include the World Geodetic System (WGS) 1984 and the North American Datum (NAD) 1983.

Projected Coordinate System (PCS): A planar coordinate system that represents the Earth's curved surface on a flat, two-dimensional map projection. Projected coordinate systems use linear units (e.g., meters or feet) and are essential for accurate area, distance, and shape calculations. Examples include Universal Transverse Mercator (UTM) and State Plane Coordinate Systems.

Vertical Coordinate System: A system used to represent and measure heights or depths, often based on a specific reference surface or datum, such as mean sea level or a local vertical datum.

Details: Proper coordinate system definition and transformation are crucial in GIS for accurate spatial data integration and overlay analysis; precise measurement of distances, areas, and shapes; correct georeferencing and positioning of data from various sources and minimizing distortions and preserving spatial relationships.

Datum

Definition: In the context of Geographic Information Systems (GIS) and spatial data management, a datum is a critical component that defines the reference frame or surface for measuring and representing locations on the Earth. It specifies the fundamental parameters that describe the Earth's shape, orientation, and origin, which are essential for accurate spatial positioning and mapping.

Details: A datum consists of several key elements:

Ellipsoid: A mathematical representation of the Earth's shape, typically an oblate spheroid or ellipsoid of revolution. The ellipsoid is defined by its semi-major axis (equatorial radius) and flattening (ratio of the difference between the equatorial and polar radii to the equatorial radius).

Origin: The point of reference or origin from which the coordinates (latitude, longitude, and height) are measured. This is often defined by the location of a specific point on the Earth's surface.

Orientation: The alignment of the coordinate system with respect to the Earth's rotational axis and a reference meridian (e.g., the Greenwich Meridian).

There are several widely used datums in GIS, including: World Geodetic System (WGS) 84, North American Datum (NAD) 83, and European Terrestrial Reference System (ETRS) 89.

DEM (Digital Elevation Model)

Definition: A Digital Elevation Model (DEM) is a digital representation of the Earth's surface elevation, typically in the form of a raster grid or a set of irregularly spaced points. It is a fundamental data source in Geographic Information Systems (GIS) and various geospatial applications, providing valuable information about the topography, terrain, and elevation characteristics of a given area.

Details: DEMs can be derived from various sources, including ground-based surveys (e.g., GPS, total stations), aerial or satellite imagery (e.g., stereoscopic photogrammetry), radar interferometry (InSAR), and Light Detection and Ranging (LiDAR) data. DEMs are widely used for a variety of purposes, including:

Terrain Modeling and Visualization: DEMs enable the creation of realistic 3D visualizations of the Earth's surface, including shaded relief maps, hillshade models, and perspective views, which are valuable for landscape analysis, urban planning, and environmental monitoring.

Hydrological and Flood Modeling: DEMs are essential for delineating watersheds, modeling water flow and drainage patterns, identifying flood-prone areas, and designing mitigation measures.

Line-of-Sight and Viewshed Analysis: DEMs are used to determine visibility and line-of-sight analyses, which are critical for telecommunication network planning, military applications, and viewshed analysis in urban and landscape design.

Slope and Aspect Calculations: DEMs allow the calculation of slope (steepness) and aspect (direction) of the terrain, which are valuable inputs for soil erosion modeling, landslide risk assessment, and various environmental and engineering analyses.

Terrain Analysis: DEMs facilitate the extraction of terrain features such as ridges, valleys, and drainage networks, which are useful for various geomorphological and geological studies.

Esri

Definition: Esri, short for Environmental Systems Research Institute, is a pioneering and leading company in the field of Geographic Information Systems (GIS) technology. Founded in 1969 and headquartered in Redlands, California, Esri is the creator and developer of the widely adopted ArcGIS software platform, which has become an industry standard for GIS applications worldwide.

Details: Esri is a privately held company that has played a pivotal role in advancing GIS technology and promoting its widespread adoption across various industries and sectors. The company's mission is to create cutting-edge GIS software, tools, and services that enable users to capture, analyze, manage, and visualize spatial data effectively.

Geocode

Definition: Geocoding is a fundamental process in Geographic Information Systems (GIS) and location-based services that involve converting textual descriptions of locations, such as street addresses, place names, or postal codes, into geographic coordinates (latitude and longitude). It establishes the spatial reference or geographic footprint of a location, enabling its precise mapping and integration with other spatial data.

Details: Geocoding is a crucial step in many GIS applications and location-based services, as it allows for mapping and spatial analysis based on location information. The process typically involves the following steps:

Address Parsing: The input address or location description is broken down into its component parts, such as street number, street name, city, state/province, and postal code.

Reference Data Matching: The parsed address components are matched against reference datasets, such as street network files, address point databases, or geographic gazetteers, to identify the corresponding geographic location.

Coordinate Interpolation: If a precise match is not found, the geocoder may use interpolation techniques to estimate the geographic coordinates based on the nearest known reference points or address ranges.

Quality Assurance: The geocoded results are typically assigned a score or confidence level based on the quality of the address match and the accuracy of the coordinates.

Geocoding enables a wide range of applications and analyses in GIS, including:

Mapping and Visualization: Geocoded locations can be plotted on maps, enabling visualizations of spatial patterns, distributions, and relationships.

Spatial Analysis: Geocoded data can be integrated with other spatial datasets, enabling analyses such as proximity, overlay, and network analysis.

Location-Based Services: Geocoding is essential for applications like navigation, ride-sharing, and location-based marketing, where precise geographic coordinates are required.

Risk Assessment and Planning: Geocoding allows organizations to map and analyze the locations of assets, customers, or events for risk assessment, resource allocation, and planning purposes.

Geodatabase

Definition: A geodatabase is a comprehensive data management and storage system designed specifically for geographic information systems (GIS) and spatial data. It is a proprietary data model developed by Esri that provides a robust and scalable framework for organizing, managing, and integrating various types of geographic and tabular data within a single database environment.

Details: A geodatabase offers a wide range of capabilities and components to support efficient and effective spatial data management, including:

Feature Classes: A feature class represents a collection of geographic features with the same geometry type (points, lines, or polygons) and a common set of attributes. It serves as the primary data structure for storing and managing spatial data in a geodatabase.

Tables: Tables store non-spatial attribute data related to geographic features or other entities, such as tabular data from spreadsheets or databases.

Relationship: Geodatabases support the definition and enforcement of relationships between feature classes, tables, and other geodatabase elements, enabling efficient data organization and integrity.

Topologies: Topologies define and maintain the spatial relationships and connectivity between geographic features, ensuring data integrity and enabling advanced spatial analysis.

Domains: Domains are used to define valid values or ranges for attribute fields, enhancing data quality and consistency.

Attribute Rules: Geodatabases allow the creation of attribute rules to enforce data integrity and validity constraints on attribute values.

Versioning: Versioning enables multiple users to edit and modify data simultaneously while maintaining historical versions and facilitating conflict resolution.

Multiuser Editing: Geodatabases support concurrent multiuser editing, allowing multiple users to access and edit the same data simultaneously, with built-in mechanisms for locking and conflict resolution.

Georeference

Definition: Georeferencing is the process of associating spatial data, such as maps, imagery, or other geographic information, with real-world coordinates or a known coordinate system. It establishes a mathematical relationship between the spatial data and its corresponding geographic location, allowing for accurate positioning and integration with other geospatial data sources.

Details: Georeferencing is a crucial step in many geographic information system (GIS) workflows, ensuring the accurate placement and alignment of spatial data within a defined coordinate system. The georeferencing process typically involves the following steps:

Identifying Ground Control Points (GCPs): GCPs are points on the spatial data (e.g., map or image) that correspond to known geographic coordinates. These points serve as reference points for establishing the spatial relationship between the data and the real-world coordinate system.

Coordinate Transformation: Using the identified GCPs, a mathematical transformation is applied to the spatial data, aligning it with the target coordinate system. Various transformation methods, such as affine, polynomial, or rubber sheeting, can be used depending on the complexity of the data and the desired accuracy.

Resampling and Warping: The spatial data is resampled and warped to fit the target coordinate system, adjusting the position and geometry of the data based on the transformation parameters.

Quality Assessment: The georeferenced data is evaluated for accuracy and quality by assessing the residual errors (differences between the transformed coordinates and the known GCPs) and visual inspection of the alignment with other reference data.

GIS (Geographic Information System)

Definition: A Geographic Information System (GIS) is a powerful technology that integrates hardware, software, data, and people to capture, store, analyze, manage, and present all forms of geographically referenced information. It is a comprehensive framework for managing, visualizing, and analyzing spatial data and their associated attributes, enabling informed decision-making across a wide range of disciplines and applications.

Details: GIS technology continues to evolve, integrating emerging technologies such as remote sensing, GPS, web services, and cloud computing, expanding its capabilities and applications. It has become an indispensable tool for understanding and managing spatial data, enabling better decision-making and addressing complex challenges across various domains.

GIS combines various components and functionalities to support spatial data management and analysis:

Data Acquisition: GIS facilitates the collection and integration of spatial data from various sources, such as satellite imagery, aerial photography, GPS, digitized maps, and survey data.

Data Management: GIS provides tools for organizing, storing, and maintaining spatial data in databases or geodatabases, ensuring data integrity, efficiency, and accessibility.

Data Analysis: GIS offers a wide range of analytical tools and techniques for spatial analysis, including overlay operations, network analysis, spatial modeling, and geostatistical analysis.

Data Visualization: GIS enables the creation of high-quality maps, 3D visualizations, and interactive web applications for effective communication and presentation of spatial information.

Decision Support: GIS serves as a powerful decision support system by integrating spatial data with other data sources, enabling spatial modeling, scenario analysis, and informed decision-making processes.

Historical Imagery: 1937

Definition: This product shows U.S.D.A. aerial imagery of Leon County, FL. The imagery was taken in 1937 and 1938 (the exact known dates are: 11/15/1937, 12/11/1937, 12/12/1937, 12/13/1937, 1/29/1938 and 3/17/1938). The images were obtained from the University of Florida Digital Collections: George A. Smathers Libraries. The images were cropped and processed in graphics software and georeferenced in ArcGIS.

Details: This shows historical imagery (1937) of Leon County, FL. TLCGIS regularly uses digital orthophotos along with planimetric, hydrographic, and topographic data to support regulatory functions, land management and acquisition, planning, engineering and habitat restoration projects. However, this imagery is not ortho-rectified.

The images displayed in this tile layer were manually scanned from hard copy then georeferenced, edge matched, and color balanced by TLCGIS staff. While TLCGIS staff georeferenced the images, we can make no claims as to the accuracy, uniformity of scale or lack of distortion. The original imagery set was missing several areas that could not be included in this product. This tile layer was published from a map tile package that was generated from an ESRI mosaic data set. Both the tile layer and the tile package are hosted in ArcGIS Online.

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Historical Imagery: 1941

Definition:This product shows U.S.D.A. aerial imagery of Leon County, FL. The imagery was taken in May, 1941. The images were obtained from the University of Florida Digital Collections: George A. Smathers Libraries. The images were cropped and processed in graphics software and georeferenced in ArcGIS.

Details: This shows historical imagery (1941) of Leon County, FL. TLCGIS regularly uses digital orthophotos along with planimetric, hydrographic, and topographic data to support regulatory functions, land management and acquisition, planning, engineering and habitat restoration projects. However, this imagery is not ortho-rectified.

The images displayed in this service were manually scanned from hard copy then georeferenced, edge matched, and color balanced by TLCGIS staff. While TLCGIS staff georeferenced the images, we can make no claims as to the accuracy, uniformity of scale or lack of distortion. This tile layer was published from a map tile package that was generated from an ESRI mosaic data set. Both the tile layer and the tile package are hosted in ArcGIS Online.

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Historical Imagery: 1949

Definition: This tile layer displays U.S.D.A. aerial imagery of Leon County, FL. The imagery was captured in 1949 (the exact known dates are 3/12/1949, 3/16/1949 and 4/6/1949). The images were obtained from the University of Florida Digital Collections: George A. Smathers Libraries. The original imagery set was missing several areas that could not be included in this product.

Details: TLCGIS regularly uses digital orthophotos along with planimetric, hydrographic, and topographic data to support regulatory functions, land management and acquisition, planning, engineering and habitat restoration projects. However, this imagery is not ortho-rectified.

The images displayed in this tile package were manually scanned from hard copy then georeferenced, edge matched, and color balanced by TLCGIS staff. While TLCGIS staff georeferenced the images, we can make no claims as to the accuracy, uniformity of scale or lack of distortion. This tile package that was generated from an ESRI mosaic data set. This tile layer was published from a map tile package that was generated from an ESRI mosaic data set. Both the tile layer and the tile package are hosted in ArcGIS Online.

This tile layer is also available for download as a tile package at: Imagery 1949 - Tile Package

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Historical Imagery: 1954

Definition: This hosted tile layer displays U.S.D.A. aerial imagery of Leon County, FL. The imagery was taken in 1954 and 1955 (the exact known dates are 12/16/1954, 12/20/1954, 1/14/1955 and 1/31/1955). The images were obtained from the University of Florida Digital Collections: George A. Smathers Libraries.

Details: TLCGIS regularly uses digital orthophotos along with planimetric, hydrographic, and topographic data to support regulatory functions, land management and acquisition, planning, engineering and habitat restoration projects. However, this imagery is not ortho-rectified.

The images displayed in this tiled layer were manually scanned from hard copy then georeferenced, edge matched, cropped, and color balanced by TLCGIS staff. While TLCGIS staff georeferenced the images, we can make no claims as to the accuracy, uniformity of scale or lack of distortion. This tile layer was published from a map tile package that was generated from an ESRI mosaic data set using ArcGIS Pro. Both the tile layer and the tile package are hosted in ArcGIS Online.

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Historical Imagery: 1954 Colorized

Definition: This hosted tile layer displays U.S.D.A. aerial imagery of Leon County, FL. The imagery was taken in 1954 and 1955 (the exact known dates are 12/16/1954, 12/20/1954, 1/14/1955 and 1/31/1955). The images were obtained from the University of Florida Digital Collections: George A. Smathers Libraries.

Details: TLCGIS regularly uses digital orthophotos along with planimetric, hydrographic, and topographic data to support regulatory functions, land management and acquisition, planning, engineering and habitat restoration projects. However, this imagery is not ortho-rectified.

The images displayed in this tiled layer were manually scanned from hard copy then georeferenced, edge matched, cropped, and color balanced by TLCGIS staff. While TLCGIS staff georeferenced the images, we can make no claims as to the accuracy, uniformity of scale or lack of distortion. This tile layer was published from a map tile package that was generated from an ESRI mosaic data set using ArcGIS Pro. Both the tile layer and the tile package are hosted in ArcGIS Online.

Colorization Process: This imagery was colorized by utilizing the Image Analyst extension in ArcGIS Pro. The Image Analyst extension allows the use of Deep Learning tools to perform Image-to-Image translation on raster data. Utilizing 2020 RGB Orthoimagery for Leon County, a CycleGAN model was trained to predict the color of pixels in TLCGIS’s set of mosaiced black-and-white imagery of Leon County, Florida.

The colors seen in this imagery should be viewed as a 'best guess' or an approximation of reality based on color values present for pixels in the imagery data that the CycleGAN model was trained on. Results can vary based on the samples fed into the model. The results presented in this imagery represents TLCGIS's best effort at translating black-and-white imagery to color (RGB).

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Historical Imagery: 1966

Definition: Black and White imagery from 1966.

Details: TLCGIS regularly uses digital orthophotos along with planimetric, hydrographic, and topographic data to support regulatory functions, land management and acquisition, planning, engineering and habitat restoration projects. However, this imagery is not ortho-rectified.

The images displayed in this service were manually scanned from hard copy then georeferenced, edge matched, and color balanced by TLCGIS staff. While TLCGIS staff georeferenced the images, we can make no claims as to the accuracy, uniformity of scale or lack of distortion. This imagery layer was published as a dynamic service from an ESRI mosaic data set.

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Historical Imagery: 1970

Definition: This tile layer shows Florida Department of Revenue aerial imagery of Leon County, FL. The imagery was taken in 1970 (the exact known date is 5/6/1970). The images were obtained from the Florida Department of Transportation: Aerial Photography Collections. This layer shows historical imagery (1970) of Leon County, FL.

Details: TLCGIS regularly uses digital orthophotos along with planimetric, hydrographic, and topographic data to support regulatory functions, land management and acquisition, planning, engineering and habitat restoration projects. However, this imagery is not ortho-rectified.

The images displayed in this service were manually scanned from hard copy then georeferenced, edge matched, and color balanced by TLCGIS staff. While TLCGIS staff georeferenced the images, we can make no claims as to the accuracy, uniformity of scale or lack of distortion. This tile layer was published from a map tile package that was generated from an ESRI mosaic data set. Both the tile layer and the tile package are hosted in ArcGIS Online.

This tile layer is also available for download as a tile package at: Imagery 1970 - Tile Package

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Historical Imagery: 1973

Definition: This tile layer displays U.S.D.A. aerial imagery of Leon County, FL. The imagery was captured in February, 1973. The images were obtained from the University of Florida Digital Collections: George A. Smathers Libraries. The images were cropped and processed in graphics software and georeferenced in ArcGIS.

Details: TLCGIS regularly uses digital orthophotos along with planimetric, hydrographic, and topographic data to support regulatory functions, land management and acquisition, planning, engineering and habitat restoration projects. However, this imagery is not ortho-rectified.

The images displayed in this service were manually scanned from hard copy then georeferenced, edge matched, and color balanced by TLCGIS staff. While TLCGIS staff georeferenced the images, we can make no claims as to the accuracy, uniformity of scale or lack of distortion. This tile layer was published from a map tile package that was generated from an ESRI mosaic data set. Both the tile layer and the tile package are hosted in ArcGIS Online.

This tile layer is also available for download as a tile package at: Imagery 1973 - Tile Package

Open in Map Viewer

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Historical Imagery: 1983

Definition: This tiled imagery layer shows Florida Department of Revenue aerial imagery of Leon County, FL. The imagery was captured in 1983 (the exact known dates are 10/28/1983, 12/7/1983, 12/15/1983). The images were obtained from the Florida Department of Transportation: Aerial Photography Collections. https://www.fdot.gov/gis/aerialproducts.shtm.

Details: TLCGIS regularly uses digital orthophotos along with planimetric, hydrographic, and topographic data to support regulatory functions, land management and acquisition, planning, engineering and habitat restoration projects. However, this imagery is not ortho-rectified.

The images displayed in this tile layer were manually scanned from hard copy then georeferenced, edge matched, and color balanced by TLCGIS staff. While TLCGIS staff georeferenced the images, we can make no claims as to the accuracy, uniformity of scale or lack of distortion. This tile layer was published from a map tile package that was generated from an ESRI mosaic data set. Both the tile layer and the tile package are hosted in ArcGIS Online.

This tile layer is also available for download as a tile package at: Imagery 1983 - Tile Package

Open in Map Viewer

Visit all TLCGIS Historical Image Content

Historical Imagery: 1990

Definition: This tile layer displays Florida Department of Revenue aerial imagery of Leon County, FL. The imagery was captured in November 1989 and January 1990 (the exact known dates are 11/17/1989, 1/11/1990, 1/13/1990 and 1/14/1990). The images were obtained from the Florida Department of Transportation: Aerial Photography Collections. https://www.fdot.gov/gis/aerialproducts.shtm.

Details: TLCGIS regularly uses digital orthophotos along with planimetric, hydrographic, and topographic data to support regulatory functions, land management and acquisition, planning, engineering and habitat restoration projects. However, this imagery is not ortho-rectified.

The images displayed in this tile layer were manually scanned from hard copy then georeferenced, edge matched, and color balanced by TLCGIS staff. While TLCGIS staff georeferenced the images, we can make no claims as to the accuracy, uniformity of scale or lack of distortion. This tile layer was published from a map tile package that was generated from an ESRI mosaic data set. Both the tile layer and the tile package are hosted in ArcGIS Online.

This tile layer is also available for download as a tile package at: Imagery 1990 - Tile Package

Open in Map Viewer

Visit all TLCGIS Historical Image Content

Layer

Definition: In a Geographic Information System (GIS), a layer is a fundamental component that represents a specific set of geographic data or thematic information within a map. Layers act as individual data overlays that can be combined, visualized, and analyzed together to create a comprehensive representation of the geographic area of interest.

Details: The power of GIS lies in the ability to overlay and integrate multiple layers, enabling spatial analysis and decision-making. By combining different layers, such as land use, population density, transportation networks, and environmental data, users can gain valuable insights, identify patterns, and make informed decisions based on the spatial relationships and interactions between these layers.

GIS layers can be organized and symbolized based on specific attributes or properties, allowing for thematic mapping and visualization of spatial patterns and relationships. Each layer can have its own set of symbology, transparency, and rendering properties, enabling users to customize the appearance and emphasize specific features or information.

Vector Data Layers: These layers consist of geometric objects such as points, lines, and polygons, representing features like cities, roads, boundaries, or land parcels. Vector data layers are typically used to represent discrete features with well-defined boundaries.

Raster Data Layers: Raster layers are composed of gridded cells or pixels, each containing a specific value. These layers are commonly used to represent continuous data, such as elevation models, satellite imagery, aerial photographs, or surface models (e.g., temperature, rainfall).

Annotation and Label Layers: These layers contain text labels, annotations, and symbols that provide additional information or context to the map, such as place names, road labels, or legends.

LiDAR

Definition:LiDAR (Light Detection and Ranging) is a remote sensing technology that uses light in the form of a pulsed laser to measure distances to the Earth. It is widely used in the field of GIS for creating detailed, high-resolution, three-dimensional models of the Earth's surface.

Details: LiDAR data can provide information about the shape of the terrain, the height of objects, and the density of vegetation. This technology is particularly useful for applications such as environmental monitoring, urban planning, and infrastructure management.

TLCGIS: uses LiDAR to generate the following content; topographic contours, spot elevations, tree canopy, digital elevation models, potential karst features, drainage boundaries, grades, 3D buildings to name a few.

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Map Document

Definition: In Geographic Information Systems (GIS), a map document is a file that contains all the information and settings required to create and display a map. It serves as a container for various map components, including data layers, symbology, layout elements, and other properties that define the appearance and behavior of the map. Map documents provide a centralized environment for organizing, styling, and publishing maps within GIS software applications.

Details: A typical map document consists of the following elements:

Data Layers: A map document can include multiple layers representing different types of geographic data, such as vector data (points, lines, polygons), raster data (imagery, elevation models), and annotation layers (labels, text).

Symbology: Each layer within the map document can be assigned specific symbology, including colors, line styles, fill patterns, and other visual properties, to effectively convey the information and enhance the map's communication and clarity.

Layout Elements: Map documents often include layout components such as legends, scale bars, north arrows, titles, and other explanatory elements that provide context and enhance the map's overall appearance and readability.

Cartographic Settings: Map documents allow users to define cartographic properties, such as coordinate systems, map projections, and spatial reference information, ensuring accurate geographic representation and enabling spatial analysis.

Geoprocessing Tools: Many GIS applications allow users to incorporate geoprocessing tools and models within map documents, enabling automated workflows and spatial analysis directly within the mapping environment.

Map documents serve several purposes in GIS workflows:

Map Authoring and Visualization: They provide a canvas for creating, styling, and visualizing maps, enabling users to explore and communicate spatial information effectively.

Map Publishing and Sharing: Map documents can be exported or published in various formats, such as printable maps, web maps, or interactive applications, allowing users to share their work with others or integrate it into different platforms.

Collaboration and Consistency: By storing all map settings and properties in a single document, multiple users can collaborate on map projects, ensuring consistency and enabling version control.

Operational Layers

Definition: Operational Layers are integral components in the creation and management of geographic information systems (GIS), particularly within the context of web maps and applications. These layers serve as the primary means of visualizing and interacting with geographic data, providing users with insights into the spatial context of information. Operational layers are essentially the core data layers that sit atop a basemap layer, offering detailed information about specific geographic areas or features.

Details: Operational layers are essential components in geographic information systems (GIS), particularly within the context of ESRI products. They serve as the foundation for visualizing and interacting with geographic data, providing a detailed representation of spatial information.

Operational layers are essentially data layers that overlay on top of a base map, offering a comprehensive view of geographic features and information. These layers can reference data from various sources, such as files or services, and are designed to enhance the user's ability to analyze and understand the spatial context of the data.

Orthoimagery and Orthorectification

Orthoimagery: Orthoimagery refers to aerial photographs that have been corrected to remove distortions caused by the camera's perspective and lens. This process, known as orthorectification, results in images that appear as if they were taken from directly overhead. Orthoimagery is used for a variety of purposes, including mapping, planning, and environmental monitoring. It provides a clear, undistorted view of the land surface, making it easier to identify features and assess environmental conditions.

Orthorectification: Orthorectification involves using control points, which are known ground locations that are accurately mapped, to correct the perspective of the aerial photographs. This process can be complex and requires a good understanding of photogrammetry and geospatial data analysis.

Visit the TLCGIS Ortho Rectified Imagery

Planimetrics

Definition: Planimetrics refers to the study and representation of two-dimensional space, specifically how geographic features are captured and represented in a two-dimensional format. This is crucial because real-world geographic elements often cannot be fully represented in two dimensions due to the limitations of a flat surface.

Details: Planimetrics is essential for creating maps, which are the primary means through which people access geographic information. It involves capturing features such as roads, building footprints, rivers, and lakes from aerial photography and digitizing them into data layers for analysis and cartographic outputs. This process allows for the accurate portrayal of three-dimensional Earth features on a two-dimensional map surface.

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Projection

Definition: Projection is a fundamental concept in Geographic Information Systems (GIS) and cartography, as it is the process of representing the curved, three-dimensional surface of the Earth onto a flat, two-dimensional plane or surface.

The Earth's surface is spherical (or more precisely, an oblate spheroid), but maps, computer screens, and other media used to display geographic data are flat. Projections are necessary to transform the Earth's curved surface onto a flat surface while preserving specific properties, such as shape, area, distance, or direction, as much as possible.

Details: Projections are essential in GIS for accurately representing, analyzing, and visualizing spatial data on flat surfaces, such as maps, computer screens, and printed materials. Understanding the characteristics and trade-offs of different projections is crucial for selecting the most appropriate projection for a given application or analysis.

All map projections introduce some form of distortion, as it is impossible to represent a three-dimensional curved surface on a flat plane without distorting some properties.

The choice of projection depends on the intended use of the map or data, the geographic extent of the area being mapped, and the specific properties that need to be preserved or minimized for distortion.

Projections are associated with specific coordinate systems, which define how positions on the Earth's surface are represented using X and Y coordinates on a flat plane. GIS software allows users to reproject data from one coordinate system to another, enabling the integration and analysis of data from different sources or projections.

There are numerous projection types, each designed to preserve or emphasize certain properties while distorting others. Some common projections include:

Cylindrical projections: Mercator, Transverse Mercator

Conical projections: Albers Equal Area, Lambert Conformal Conic

Azimuthal or Planar projections: Gnomonic, Stereographic

Different projections prioritize the preservation of different properties, such as:

Conformality: Preserving local shape

Equivalence: Preserving area

Equidistance: Preserving distance from a specified point or line

Raster Data

Definition: Raster data is a fundamental data model used in Geographic Information Systems (GIS) to represent and store spatial information.

As mentioned in the definition, raster data is organized as a grid or matrix of cells (also called pixels). Each cell in the matrix represents a specific area on the Earth's surface, and the value stored in the cell represents a particular attribute or measurement for that location.

The resolution of a raster dataset refers to the size of the cells or pixels. Higher resolution means smaller cell sizes, resulting in more detailed and precise representation of spatial features. Lower resolution implies larger cell sizes, leading to a more generalized representation.

Details: Raster data plays a crucial role in GIS, particularly in applications involving remote sensing, terrain analysis, environmental modeling, and spatial analysis of continuous phenomena. It complements vector data, which is better suited for representing discrete features with precise boundaries and locations.

GIS software provides a range of tools and functions for analyzing and processing raster data, such as:

Overlay analysis: Combining multiple raster datasets to create new derived datasets.

Reclassification: Assigning new values to cells based on specific criteria.

Neighborhood analysis: Analyzing the values of surrounding cells (e.g., focal statistics, filters).

Surface analysis: Generating contours, slope, aspect, viewsheds, and other surface-derived products.

Reference Layers

Definition: Reference Layers serve a key role in maps by providing geographic context and orienting map readers. These layers contain features and labels that aid in identifying locations, understanding landscape patterns, and interpreting operational data layers.

Details: Typical reference layer content includes place names, transportation networks, landmarks, political boundaries, and terrain representations. By drawing on top of other map layers, reference features remain visible to map users for geographic orientation. For example, a reference layer may contain city names and major highways overlaid on aerial imagery.

Effective reference layers are unobtrusive and aesthetically subtle, complementing rather than competing with operational map content. Features and symbols should be large and clear enough for legibility without overpowering. Reference information is applied judiciously, highlighting key identifiers and patterns without excessive clutter.

Reference layers are often incorporated into basemaps, but can also be accessed as standalone content. This allows the flexibility to adjust the level of reference detail as needed for particular mapping purposes. Options may range from minimal reference context to richer layers showing diverse landmarks, boundaries, and annotations.

Shapefile

Definition: Shapefiles are a vector data format, which means they store spatial features as points, lines, and polygons, rather than a grid of cells like raster data. This makes shapefiles well-suited for representing discrete features with precise geometries and locations.

Details: A shapefile is not a single file but rather a collection of related files with different extensions:

.shp: The main file that stores the geometry of the spatial features.

.shx: The index file that links the geometry data with the attribute data.

.dbf: The dBASE file that stores the attribute data (non-spatial information) associated with each feature.

.prj: The projection file that defines the coordinate system and projection used for the data.

.xml, .cpg, etc.: Additional optional files that may contain metadata or other information.

TLCGIS Basemap Gallery

Definition: The TLCGIS Basemap Gallery is a comprehensive collection of basemaps that are readily accessible to all users within the TLCGIS's ArcGIS Online Organization. This gallery is meticulously curated by TLCGIS staff, incorporating locally maintained layers and imagery. Given TLCGIS's role as a local agency with authoritative content, it has the capability to develop and sustain custom basemaps tailored to the specific needs of its agency. These custom basemaps are updated more frequently than those provided by ESRI, ensuring that users have access to the most current and relevant mapping information.

Details: To integrate a basemap into an active map within ArcGIS Pro, users navigate to the Map tab, select Basemap from the Layer group, and choose from the options available in the basemap gallery. Only one basemap can be utilized per map, and this process updates or adds the selected basemap to the map. The TLCGIS Basemap Gallery offers a valuable resource for local agencies, providing custom basemaps that are curated and updated frequently to meet specific needs.

Visit the TLCGIS Basemap Gallery

Topology

Definition: In GIS, topology refers to the spatial relationships and connectivity between geographic features or elements. It defines how different geometric objects (points, lines, and polygons) are related and interact with each other. The main concepts of topology in GIS include:

Connectivity: Topology ensures that linear features (lines) are connected or disconnected correctly, and polygons have a closed boundary with no dangles or overshoots.

Containment: It defines how areas (polygons) can contain other areas, lines, or points within their boundaries.

Adjacency: Topology maintains information about which polygons are adjacent to or share boundaries with each other.

Networks: It allows the modeling and analysis of network datasets, such as transportation networks, utility networks, or hydrological networks, where connectivity and directionality are essential.

Details: Topology deals with connectivity, continuity, and spatial relationships among geographic features. Examples include ensuring that road networks are properly connected without any dangles or undershoots, maintaining the integrity of parcel boundaries where polygons must not overlap, and modeling the flow direction in a river network based on topological relationships between line segments.

Despite some limitations, shapefiles remain a popular and widely used vector data format in GIS due to their simplicity, portability, and broad software support. They are commonly used for storing and exchanging spatial data, performing spatial analysis, and creating maps and other visualizations.

Topography

Definition: Topography refers to the study and representation of the physical features and terrain of an area, including natural and artificial features. It plays a crucial role in various fields, including geography, cartography, urban planning, and environmental studies.

Details: Topography is a fundamental aspect of understanding the Earth's surface and plays a crucial role in various applications, from navigation and urban planning to environmental management and disaster preparedness. Accurate topographic data and representations are essential for informed decision-making and effective management of natural and built environments.

Elements of Topography:

Relief: The variations in elevation, including mountains, hills, valleys, and plains.

Drainage: The network of water bodies, such as rivers, streams, lakes, and wetlands.

Vegetation: The distribution and types of plant life, including forests, grasslands, and cultivated areas.

Man-made features: Structures and infrastructure created by humans, such as buildings, roads, bridges, and dams.

Topographic Data Collection:

Field surveys: Collecting data through direct observations, measurements, and mapping techniques.

Remote sensing: Using aerial photography, satellite imagery, and other remote sensing technologies to capture topographic data from a distance.

Cartographic sources: Extracting topographic information from existing maps, charts, and other cartographic materials.

Topographic Representation:

Topographic maps: Specialized maps that depict the three-dimensional features of an area using contour lines, shading, and symbols.

Digital Elevation Models (DEMs): Raster-based representations of terrain elevation, often used in GIS for analysis and visualization.

3D models: Computer-generated models that provide a realistic and interactive representation of terrain and features.

Vector Data

Definition: Vector data is a fundamental data model used in Geographic Information Systems (GIS) to represent and store spatial information. It is particularly well-suited for representing discrete features with precise geometries and locations.

Details: Vector data plays a crucial role in GIS, particularly in applications involving mapping, spatial analysis, and modeling of discrete features. It is often used in conjunction with raster data, which is better suited for representing continuous phenomena and surfaces.

Various vector data formats exist, such as shapefiles, geodatabases, and GML (Geography Markup Language), each with its own strengths and applications. GIS software provides tools for creating, editing, analyzing, and visualizing vector data, enabling efficient management and analysis of spatial information.

Geometric Primitives:

Points: Represent discrete locations or events, such as cities, landmarks, or sampling sites.

Lines (or polylines): Represent linear features or paths, such as roads, rivers, pipelines, or contour lines.

Polygons: Represent enclosed areas or boundaries, such as land parcels, lakes, political boundaries, or building footprints.

Coordinate-Based Representation:

Vector data represents spatial features using a series of ordered coordinate pairs (x, y) or triplets (x, y, z) in a specific coordinate system.

These coordinates define the precise location and shape of the features on the Earth's surface or in a projected coordinate system.

Attribute Data:

In addition to geometric information, vector data can store attribute data or descriptive information associated with each feature.

Attribute data can include various types of information, such as names, categories, numeric values, or other characteristics related to the features.

Topological Relationships:

Vector data models often support topological relationships, which describe how features are spatially related to one another.

Examples of topological relationships include connectivity (e.g., road networks), adjacency (e.g., land parcels), and containment (e.g., buildings within a city boundary).

Data Sources and Creation:

Vector data can be created manually through digitizing or tracing features from maps, aerial photographs, or satellite imagery.

It can also be derived from field surveys using Global Positioning System (GPS) devices or other survey equipment.

Many government agencies and organizations distribute vector data in standardized formats, such as shapefiles or geodatabases.

Web Layers

Definition: layers within ESRI products provide a robust framework for visualizing and interacting with geographic data. They are designed to be responsive, efficient, and up-to-date, offering a comprehensive and dynamic view of spatial information. Whether through feature layers, map image layers, or tile layers, these operational layers play a crucial role in enhancing the user's ability to analyze and understand the spatial context of the data.

Web Feature Layers:

Web feature layers are a type of operational layer that supports feature querying, visualization, and editing. They are configured with properties like symbology, labeling, pop-ups, time, and feature templates, ensuring that the web map experience mirrors the design created in ArcGIS Pro. This consistency in user experience is crucial for effective data analysis and decision-making.

Map Image Layers:

Map image layers are another form of operational layer, are available when sharing to ArcGIS Enterprise. These layers can be either dynamic or cached and support both map visualization and feature querying. They offer a wide range of symbology options and automatically update to reflect changes in the source data, making them a powerful tool for maintaining up-to-date map representations.

Tile Layers:

Tile layers, specifically vector tile layers, offer a highly efficient way to visualize complex geometries at small scales. They are designed to optimize drawing performance, making them an excellent choice for applications that require fast visualization of large datasets. Vector tile layers are smaller in size compared to raster tile layers, which can significantly reduce loading times and improve the overall user experience.

Webmap

Definition: A webmap is a digital map that is designed to be shared and viewed online. It is created using web mapping technologies and can be accessed through a web browser. Webmaps can include various types of data layers, such as basemaps, feature layers, and operational layers, allowing users to visualize and interact with geographic information. They are highly customizable, enabling users to adjust the appearance, add annotations, and share the map with others. Webmaps are commonly used for public access, planning, and decision-making processes, providing a convenient way to share geographic information and analyses.