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Data Dictionary

Here you will find a dictionary of definitions for the primary datasets in the Data Catalog. If you would like further information, please contact our data support.

Adjacent States

This generalized dataset represents the states that border the state of Texas (Arkansas, Louisiana, Oklahoma, and New Mexico). The dataset is useful for reference when displaying Texas at its fullest extent and has been generalized to improve draw performance. Largest scale when displaying the data: 1:3,000,000.

Airports

The Public-Use Airports database, from the Bureau of Transportation Statistics, is a geographic point database of aircraft landing facilities in the United States and U.S. Territories. Attribute data is provided on the physical and operational characteristics of the landing facility, current usage including enplanements and aircraft operations, congestion levels and usage categories. The database provides location and attribute information for use in national and regional cartographic and spatial analysis applications.

Aquifers

TNRIS carries a digital version of the major and minor aquifers of Texas and categorizes them according to their outcrop and down dip sections. An outcrop is that part of a water-bearing rock that appears at the land surface, and a down dip is the part that dips below other rock layers.

Bathymetry

New bathymetry of the Texas-Louisiana Continental Shelf was compiled in a project carried out in 2004 - 2006 sponsored by the Texas Sea Grant College Program. The objective of this project was to provide for the first time new bathymetry as good as the available underlying historical U. S. Coast Survey bathymetric survey data.

Digital Elevation Model (DEM)

The U.S. Geological Survey (USGS) DEM data files are digital representations of ground surface topography or terrain. DEM’s consist of a sampled array of elevations for a number of ground positions at regularly spaced intervals. The quality of a DEM is a measure of how accurate elevation is at each pixel (absolute accuracy) and how accurately is the morphology presented (relative accuracy). Several factors play an important role for quality of DEM’s: terrain roughness, sampling density, elevation data collection method, Interpolation algorithm, vertical resolution, and terrain analysis algorithms.

Digital Ortho Quadrangle (DOQ)

Digital ortho-photographs are aerial photos that have been geometrically corrected to remove distortions. They have all the properties of a map, combined with the features of an aerial photo. Unlike an uncorrected aerial photograph, an ortho-photo can be used to measure true distances because it is an accurate representation of the earth's surface, having been adjusted for topographic relief, lens distortion, and camera tilt. Software can display the ortho-photo and allow a user to 'digitize' or place line-work, text annotations and geographic symbols.

Digital Raster Graphics (DRG)

A digital raster graphic (DRG) is a scanned image of a USGS standard series topographic map, including all map collar information. The image inside the map neatline is georeferenced to the surface of the earth and fit to the Universal Transverse Mercator projection. The horizontal positional accuracy and datum of the DRG matches the accuracy and datum of the source map. The map is scanned at a minimum resolution of 250 dots per inch. Available scales: 1:24,000 or 7.5 by 7.5 minute quadrangle maps, 1:100,000 or 30 by 60 minute quadrangle maps, and 1:250,000 or 1 by 2 degree quadrangle maps.

DOT Roadways

TXDOT GIS centerline based inventory of the state maintained roads. The routes are a comprehensive routed GIS centerline basemap for the State of Texas. The routes are a polylineM feature type with measures starting at the beginning of the route.

FEMA Q3 Flood Data

The digital Q3 Flood Data was created by scanning the effective Flood Insurance Rate Map (FIRM) paper maps and digitizing selected features and lines. The data are designed to serve FEMA's needs for disaster response activities, National Flood Insurance Program activities, risk assessment, and floodplain management. Because digital Q3 Flood Data are controlled to the USGS 1:24,000 scale maps, they may not be detailed enough for some uses. The hardcopy FIRM or Digital Flood Insurance Rate Map should be used to make official determinations, especially if a property is close to the boundary of a mapped special flood hazard area.

Geologic Atlas of Texas (GAT)

The Geologic Atlas of Texas was created as part of the conversion of the University of Texas, Bureau of Economic Geology Geologic Atlas of Texas map sheets. The information in this map was captured at 1:250,000 scale. These data should not be used for mapping at scales larger than 1:250,000. TNRIS carries the GAT in both raster and vector formats. The raster format is a scanned and geo-referenced version of the original Geologic Atlas sheets. The vector version has been digitized off the scanned sheets.

Hydrologic Unit Code (HUC)

Hydrologic unit boundaries define the aerial extent of surface water drainage to a point. Hydrologic units through four levels were created in the 1970's and have been used extensively throughout the United States. During that time the USGS developed a hierarchical hydrologic unit code for the US. This system divides the country into 21 Regions, 222 Sub regions, 352 Accounting Units, and 2,149 Cataloging Units based on surface hydrologic features. The smallest USGS unit (8-digit HU) is approximately 448,000 acres.

LandSAT 7

LandSAT represents the world’s longest continuously acquired collection of space-based land remote sensing data. The LandSAT Project is a joint initiative (USGS & NASA) designed to gather Earth resource data from space. NASA developed and launched the spacecrafts, while the USGS handles the operations, maintenance, and management of all ground data reception, processing, archiving, product generation, and distribution. LandSAT’s Global Survey Mission is to repeatedly capture images of the Earth’s land mass, coastal boundaries, and coral reefs, and to ensure that sufficient data are acquired to support the observation of changes on the Earth’s land surface and surrounding environment.

Light Detection and Ranging (LiDAR)

LiDAR is an optical remote sensing technology that measures properties of scattered light to find range and/or other information of a distant target. Like the similar radar technology, which uses radio waves instead of light, the range to an object is determined by measuring the time delay between transmission of a pulse and detection of the reflected signal. LiDAR technology has application in geography, geology, geomorphology, seismology, remote sensing and atmospheric physics.

National Agriculture Imagery Program (NAIP)

NAIP imagery is available as quarter quadrangle tiles or as compressed county mosaics. The mosaics are generated by compressing digital quarter quadrangle image tiles scanned from natural color positive or color infrared positive aerial film into a single mosaic. The mosaic may cover all or portions of an individual final product. Each individual image tile within the mosaic covers a 3.75 x 3.75 minute quarter quadrangle plus a 300 meter buffer on all four sides. All individual tile images and the resulting mosaic were rectified to the UTM coordinate system, NAD 83, and cast into a single predetermined UTM zone.

National Elevation Data (NED)

The National Elevation Dataset (NED) is a raster product assembled by USGS. NED is designed to provide national elevation data in a seamless form with a consistent datum, elevation unit, and projection. Data corrections were made in the NED assembly process to minimize artifacts, perform edge matching, and fill sliver areas of missing data. NED is the result of the maturation of the USGS effort to provide 1:24,000-scale Digital Elevation Model (DEM) data for the conterminous US and 1:63,360-scale DEM data for Alaska.

National Hydrography Dataset (NHD)

The 1:24,000 National Hydrography Dataset (NHD), jointly developed by the USGS and the Environmental Protection Agency (EPA), is a hydrologic data network designed to show all surface water features including rivers and streams, ponds and lakes, springs, canals, wetlands, and shorelines. The NHD dataset allows stream conditions to be modeled enabling the user to predict the downstream impact of a flood event. Also available is a generalized statewide hydrographic dataset which provides unique stream and river identification codes and flow information at the 1:100,000 scale. The NHD dataset can be downloaded directly from the USGS NHD website.

Natural Regions

This dataset was set up as a system to identify broad natural regions of Texas, to serve as a common point of reference for scientists, students, visitors and all citizens of Texas; and to locate and recommend for preservation natural areas that contain unique, significant, unusual and scenic resources, including rare or endangered species and endangered geological formations and ecosystems, with the goal of preserving elements of Texas natural diversity.

Original Texas Land Survey (OTLS)

The Original Texas Land Survey (OTLS) is an interpretation of the Original Texas Land Surveys boundaries and bay tracts. The dataset was derived from the Texas General Land Office (GLO) county maps, the GLO Abstract of Original Land Titles: Volumes and Supplements, and the GLO maps of State-Owned Submerged Lands of the Texas Gulf Coast (bay tracts). The OTLS was generated by the Texas Railroad Commission. The Patent Survey lines from the Texas General Land Office (GLO) maps are interpreted against the USGS 7.5 minute quadrangle maps to create the OTLS layer. The OTLS is continually updated and refined by the RRC.

Precipitation

This dataset contains vector and raster layers of average monthly and annual precipitation for the climatologically period between 1961 and 1990. Parameter elevation Regressions on Independent Slopes Model (PRISM) derived raster data is the underlying data set from which the polygons and vectors were created. PRISM is an analytical model that uses point data and a digital elevation model (DEM) to generate gridded estimates of annual, monthly and event-based climatic parameters. Detailed descriptions of the PRISM raster data can be found with the accompanying raster data sets.

Railroads

The statewide railroad layer was originally digitized from the USGS 7.5 quadrangles by TXDOT. The railroad layer was extracted from the TxDOT county\urban files and photo revised to match the 1995 TOP aerial photography. The layer was attributed by using both TxDOT and Texas Railroad Commission information. This layer will be continually updated to reflect the most current information.

Reservoirs

This dataset was digitized off of 1:250,000 Bureau of Economic Geology maps in 1995. The reservoirs selected generally have authorized capacities of 5,000 acre-feet or more and authorized diversions of water for municipal, industrial and irrigational consumptive and non-consumptive use.

Shuttle Radar Topography Mission (SRTM)

The Shuttle Radar Topography Mission is an international project spearheaded by the U.S. National Geospatial-Intelligence Agency (NGA) and NASA. The project developed digital elevation models on a near-global scale from 56 °S to 60 °N, to generate the most complete high-resolution digital topographic database of Earth to date. SRTM consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during the 11-day STS-99 mission in February of 2000.

SPOT

SPOT is a high-resolution, optical imaging earth observation satellite system operated by Spot Image based in Toulouse, France. It was initiated by the CNES (French space agency) in the 1970’s and developed in association with the SSTC (Belgian scientific, technical and cultural services) and the Swedish National Space Board (SNSB). It has been designed to improve the knowledge and management of the earth by exploring the earth's resources, detecting and forecasting phenomena involving climatology and oceanography, and monitoring human activities and natural phenomena. The SPOT system includes a series of satellites and ground control resources for satellite control and programming, image production and distribution.

SSURGO-Soils

The SSURGO dataset was developed in partnership with the Natural Resources Conservation Service and is an updated digital version of the county soil surveys. SSURGO uses recent digital ortho-photos and field work to update the original printed surveys. StratMap and the NRCS joined forces to create the soil survey geographic database for Texas. This data set is a digital soil survey and is the most detailed level of soil geographic data developed by the National Cooperative Soil Survey. The soil map units are linked to attributes in the National Soil Information System relational database, which gives the proportionate extent of the component soils and their properties.

StratMap Boundaries

The StratMap political boundary dataset contains political jurisdictions, state boundaries, county boundaries, city boundaries, federal parks, state parks, and landmark boundaries (airports, universities, wildlife refuges, and military bases). StratMap Boundaries are useful in right-of-way determination, highway planning and maintenance, real estate, public services, jurisdiction maintenance, and numerous administrative assignments. Each of the boundary datasets are derived from various sources such as the Texas Department of Transportation, Texas Parks and Wildlife, and local jurisdictions to create the most comprehensive datasets available.

StratMap Hypsography

Elevation contour DLG’s (digital line graphics) are digital versions of the contour lines on all 7.5 minute, 1:24,000 scale USGS quadrangle maps. Elevation contours are also referred to as hypsography, meaning topographic relief. The contour interval used for StratMap digital contours is the same as that found on 7.5 minute USGS maps. Contour lines can be used to create digital elevation models (DEM’s).

StratMap Transportation

The StratMap transportation layer is an updated, digital version of the transportation features found on the 7.5 minute, 1:24,000 scale USGS quadrangle maps. Where available, digital ortho-photography and GPS data are used to improve positional accuracy. Transportation features encompass all public roads in Texas, including city streets, state and federal highways, interstates, and selected private roads. The transportation layer is designed to be a universal transportation layer that can be integrated into a GIS application or project. The StratMap statewide transportation dataset is a publicly available digital data layer which serves as a cartographic product for seamless basemap production.

Texas Gazetteer

The Texas Gazetteer was developed to meet national and state needs by providing information for named entities in the United States, its territories, and outlying areas. Place names are of either cultural features such as schools, hospitals, cemeteries, etc., or physical features such as rivers, lakes, and summits. In all, over 25 feature tables constitute the database and supplement the already 55, 000 place names in the system, for a total of over 100,000 geographic names for Texas.

Texas Orthographic Program (TOP)

The original Texas Orthographic Program photos were derived from 1:40,000 NAPP color-infrared (CIR) taken from 1994-1997. TNRIS has these images in several resolutions (1m, 2.5m, and 10m). County mosaics of the original TOP aerial photos are also available.

TxDOT CRIP Roadways

TXDOT GIS centerline based inventory of the county roads. The routes are a comprehensive routed GIS centerline basemap for the State of Texas. The CRIP is a GPS data collection project.

TxDOT Urban Files

The TxDOT Urban files are provided in three data formats ".dgn", ".dwg", and ".e00". TxDOT supplies the data in native .dgn format. TNRIS creates ".dwg" and ".e00" files by converting the dgn file using the conversion tools available in ArcGIS. During this conversion process, some annotation will not convert to the other formats leaving features without attribution. TxDOT has stopped updating the dgn files in 2003 however; the data is still available and is organized by County Name on our FTP site. The metadata file can also be found in the root of the directory.

US Census Bureau

TNRIS houses US Census Bureau data commonly found in Census TIGER files. Available datasets for the state of Texas: Census Urban Areas, Census Tracts, Census Block Groups, Census Blocks, Census Demographics, Census Economics, Census Housing, and Census Social data.

USGS Quadrangle Indices

The word "quadrangle" refers to a USGS 7.5-minute quadrangle map, which is usually named after a local physiographic feature. On a USGS 7.5-minute quadrangle map, the north and south limits of the quadrangle are not straight lines, but are actually curved to match Earth's lines of latitude on the standard projection. The east and west limits are usually not parallel as they match Earth's lines of longitude. The dataset was created to assist with locating the names and indexing information associated with each quadrangle and their approximate boundaries.

Zip Codes

U.S. ZIP Code Areas represents five-digit ZIP Code areas used by the U.S. Postal Service to deliver mail more effectively. The first digit of a five-digit ZIP Code divides the country into 10 large groups of states numbered from 0 in the Northeast to 9 in the far West. Within these areas, each state is divided into an average of 10 smaller geographical areas, identified by the 2nd and 3rd digits. These digits, in conjunction with the first digit, represent a sectional center facility or a mail processing facility area. The 4th and 5th digits identify a post office, station, branch or local delivery area.

Layer Spotlight

Layer Spotlight is a new way to showcase the rich, extensive geographic data housed at TNRIS. It is a chance to view and explore a data layer before downloading.

It is part of the implementation of a new data viewing application incorporating Microsoft Virtual Earth® software. In the future, as TNRIS further develops its data dissemination tools, keep an eye out for even more robust and dynamic applications.

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