This GIS data set is a digital general soil association map of North Carolina developed by the National Cooperative Soil Survey. It consists of a broad based inventory of soils and nonsoil areas that occur in a repeatable pattern on the landscape and that can be cartographically shown at the scale mapped. The soil maps for STATSGO are compiled by generalizing more detailed soil survey maps. Where more detailed soil survey maps are not available, data on geology, topography, vegetation, and climate are assembled, together with Land Remote Sensing Satellite (LANDSAT) images. Soils of like areas are studied, and the probable classification and extent of the soils are determined. Map unit composition for a STATSGO map is determined by transecting or sampling areas on the more detailed maps and expanding the data statistically to characterize the whole map unit. This data set consists of georeferenced digital map data and computerized attribute data. The map data are collected in 1- by 2-degree topographic quadrangle units and merged and distributed as statewide coverages. The soil map units are linked to attributes in the Map Unit Interpretations Record relational data base which gives the proportionate extent of the component soils and their properties.
STATSGO depicts information about soil features on or near the surface of the Earth. These data are collected as part of the National Cooperative Soil Survey.
> >There are 13 associated text files of soils characteristics >which are keep offline on magnetic media. No interpretations >of these characteristics have been made by CGIA: >comp; compyld; forest; interp; layer; mapunit; plantnm; >taxclass, windbrk; wlhabit; woodland; woodmgt; yldunits >http://www.cgia.state.nc.us/corpmeta.dir/gslnctab.txt >13 associated tables combined into 1 ascii text file, 2.1 mb > >system filename: gslnc250 approx. file size = 3.3 mb >filename: gslnc250tab.txt. File added in 1993. > >Revisions and updates to this layer include: >2.) filename: gslnc2501298 The December 1998 update to this >layer consisted of projecting the data from NAD27 datum, State >Plane projection, units of measure feet TO: NAD83 DATUM, State >Plane PROJECTION, UNITS OF MEASURE METERS. This was done to >comply with the NC Geographic Information Coordinating Council's >"Statement of Direction for North Carolina Corporate Geographic >Database Horizontal Reference, Datum and Unit of Measure". >This reprojecting was done in various ways depending on the >data type and content. Vector data was projected using the >'project' command in ESRI's Arc software and topology was >cleaned and built based on coverage needs. Raster data was >projected using ESRI's Grid module and various steps as applicable. >1.) filename: nc250gsl88 This 1988 file is the original >data and has not been edited. (previously called nc250.gsl)
The U.S. Department of Agriculture, Natural Resource Conservation Service should be acknowledged as the data source in products derived from these data. STATSGO was designed primarily for regional, multicounty, river basin, State, and multistate resource planning, management, and monitoring. STATSGO data are not detailed enough to make interpretations at a county level. This soil survey product is not designed for use as a primary regulatory tool in permitting or citing decisions, but may be used as a reference source. The use of these data is not restricted and may be interpreted by organizations, agencies, units of government, or others; however, they are responsible for its appropriate application. Federal, State, or local regulatory bodies are not to reassign to the Soil Conservation Service any authority for the decisions that they make. The Natural Resources Conservation Service will not perform any evaluations of these maps for purposes related solely to state or local regulatory programs. When STATSGO data are overlayed with other data layers, such as land use data, caution must be used in generating statistics on the co-occurrence of the land use data with the soil data. The composition of the STATSGO map unit can be characterized independently for the land use and for the soil component, but there are no data on their joint occurrence at a more detailed level. Analysis of the overlayed data should be on a map polygon basis. Additional political, watershed, or other boundaries may be intersected with the soil data. Although the composition of each political and watershed unit may be described in terms of the STATSGO map units, information is not available to assign the components to the boundary units with full accuracy. As with the land use categories, the analysis should be restricted to the classified components. The approximate minimum area delineated is 625 hectares (1,544 acres), which is represented on a 1:250,000-scale map by an area approximately 1 cm by 1 cm (0.4 inch by 0.4 inch). Linear delineations are not less than 0.5 cm (0.2 inch) in width. The number of delineations per 1:250,000 quadrangle typically is 100 to 200, but may range up to 400. Delineations depict the dominant soils making up the landscape. Other dissimilar soils, too small to be delineated, are present within a delineation. Digital enlargements of these maps to scales greater than at which they were originally mapped can cause misinterpretation of the data. If enlarged, maps do not show the small areas of contrasting soils that could have been shown at a larger scale. The depicted soil boundaries, interpretations, and analysis derived from them do not eliminate the need for onsite sampling, testing, and detailed study of specific sites for intensive uses. Thus, these data and their interpretations are intended for planning purposes only. Attribute data for some data elements may be incomplete or missing. Where data are unavailable, a mask should be used to exclude the area from analysis. Digital data files are periodically updated. Files are dated, and users are responsible for obtaining the latest version of the data.
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>NCCGIA Director, Karen Siderelis >Database Administration, Zsolt Nagy >Database Management, Ken Shaffer >North Carolina Center for Geographic Information and Analysis >Governor's Office >Office of State Planning >301 North Wilmington Street, Suite 700 >Raleigh, NC 27601-2825 > >U.S. Dept. of Agriculture, >Natural Resource Conservation Service >Fort Worth, TX
Attribute accuracy is tested by manual comparison of the source with hard copy plots and/or symbolized display of the map data on an interactive computer graphic system. Selected attributes that cannot be visually verified on plots or on screen are interactively queried and verified on screen. In addition, the attributes are tested against a master set of valid attributes. All attribute data conform to the attribute codes in the signed classification and correlation document and amendments and are current as of the date of digitizing.
Certain node/geometry and topology (GT)-polygon/chain relationships are collected or generated to satisfy topological requirements. (The GT-polygon corresponds to the soil delineation). Some of these requirements include: chains must begin and end at nodes, chains must connect to each other at nodes, chains do not extend through nodes, left and right GT-polygons are defined for each chain element and are consistent throughout, and the chains representing the limits of the file (neatline) are free of gaps. The tests of logical consistency are performed using vendor software. The neatline is generated by connecting the explicitly entered four corners of the digital file. All data outside the enclosed region are ignored and all data crossing these geographically straight lines are clipped at the neatline. Data within a specified tolerance of the neatline are snapped to the neatline. Neatline straightening aligns the digitized edges of the digital data with the generated neatline (i.e., with the longitude/latitude lines in geographic coordinates). All internal polygons are tested for closure with vendor software and are checked on hard copy plots. All data are checked for common soil lines (i.e., adjacent polygons with the same label). Quadrangles are edge matched within the state, merged into a statewide data sets, and then edge matched to adjacent state data sets. Edge locations do not deviate from centerline to centerline by more than 0.01 inches.
A map unit is a collection of areas defined and named the same in terms of their soil and/or nonsoil areas. Each map unit differs in some respect from all others in a survey area and is uniquely identified. Each individual area is a delineation. Each map unit consists of one to 21 components. In those few areas where detailed maps did not exist, reconnaissance soil surveys were combined with data on geology, topography, vegetation, climate, and remote sensing images to delineate map units and estimate the percentages of components. The STATSGO map unit components are soil series phases, and their percent composition represents the estimated areal proportion of each within STATSGO map unit. The composition for a map unit is generalized to represent the statewide extent of that map unit and not the extent of any single map unit delineation. These specifications provide a nationally consistent representation of STATSGO attribute data. The actual composition and interpretive purity of the map unit delineations were based on statistical analysis of transect data. The composition was largely determined by measuring transects on detailed soil survey maps. The number of transects used was proportional to the relative size, number, and complexity of the delineations. The combined data on the length of the map units crossed by the transects were used to determine the percentages of the different soil and nonsoil areas in each map unit. Specific limits were established on the classification of soils and the design and name of map units. These limits are outlined in U.S. Department of Agriculture. 1975. Soil Taxonomy A basic system of soil classification for making and interpreting soil surveys. Soil Conserv. Serv., U.S. Dep. Agric. Handb. 436.; U.S. Department of Agriculture. 1992. Keys to Soil Taxonomy. SMSS Technical Monograph No. 19. Soil Surv. Staff, Soil Conserv. Serv.; U.S. Department of Agriculture. 1993. National Soil Survey Handbook, title 430-VI. Soil Surv. Staff, Soil Conserv. Serv.; and U.S. Department of Agriculture. 1993. Soil Survey Manual. Soil Surv. Staff, U.S. Dep. Agric. Handbook 18. Adherence to National Cooperative Soil Survey standards and procedures is based on peer review, quality control, and quality assurance. Quality control is outlined in documents that reside with the Natural Resources Conservation Service state soil scientist.
The accuracy of these digital data is based upon their compilation to base maps that meet National Map Accuracy Standards. The difference in positional accuracy between the map unit boundaries in the field and their digitized map locations is unknown. The locational accuracy of soil delineations on the ground varies with the transition between map units. For example, in areas where changes in soils, climate, topography, and geology occur subtly across a portion of a state, the transition between soil map unit boundaries will be gradual. Where these features change abruptly, such as from an area of foothills to a lake plain, the transition will be very narrow. Soil delineation boundaries were digitized within 0.01 inches of their locations on the digitizing source. The digital map elements are edge matched between data sets. The data along each state boundary are matched against the data for the adjacent state. Edge locations generally do not deviate from centerline to centerline by more than 0.01 inch.
base information for development of map unit delineations and transect data for naming map units
reference information for development of map unit delineations and transect data for naming map units where detailed surveys did not exist
base materials for compilation of map unit delineation linework
Digital data set was projected to NAD83, state plane, meters
Map unit composition was determined by transecting or sampling areas on the more detailed soil maps and expanding the data statistically to characterize the whole map unit.
Soil map unit lines and symbols were drafted in red pencil on a mylar overlay that was punch registered to fit the mylar USGS 1:250,000-scale topographic quadrangle. A detailed and complete edit was performed on all overlays before digitizing. The soil delineation overlays were raster scanned at a scanning resolution of at least 0.01 inches and converted to a vector format or were manually digitized on a digitizing tablet with a resolution of at least 0.001 inches. Four control points corresponding to the four corners of the quadrangles were used for registration during data collection. The control points were either explicitly entered or developed by the software. The data sets were edge matched and merged into statewide coverages. A detailed and complete edit was performed on all digital data.
Using ESRI's ARC/INFO software, the digital data set was post processed and projected into NAD27 datum, Stateplane coordinate system, NC Zone 4901, meters units of measure.
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Internal feature number.
Total perimeter in coverage units
Internal feature number.
From-node identifier of linear feature
To-node identifier of linear feature
Internal number of poly to left of arc
Internal number of poly to right of arc
Length of arc in coverage units
Internal feature number
Internal identification number
A polygon coverage depicting general soil types for North Carolina as classified by the US Department of Agriculture, Natural Resources Conservation Service. The polygon attribute table (PAT) has attribute data including total area in coverage units (square meters), total perimeter (linear meters), polygon internal identification number, polygon user identification number, and a soil number identifying its classification. >GSLNC250.PAT Polygon Attribute Table >COLUMN ITEM NAME WIDTH OUTPUT TYPE DEC DESCRIPTION >1 AREA 4 12 F 3 Total area in meters >5 PERIMETER 4 12 F 3 Total perimeter in meters >9 gslnc250# 4 5 B - Poly internal id number >13 gslnc250-ID 4 5 B - Poly user id number >17 GSL-NAME 6 7 C 0 Soil number used to identify >classification and relate to STATSGO tables >GSLNC250.AAT Arc Attribute Table >COLUMN ITEM NAME WIDTH OUTPUT TYPE DEC DESCRIPTION >1 FNODE# 4 5 B - From-node id of linear feature >5 TNODE# 4 5 B - To-node id of linear feature >9 LPOLY# 4 5 B - Left-side polygon id of linear >feature >13 RPOLY# 4 5 B - Right-side polygon id of linear >feature >17 LENGTH 4 12 F 3 Length of linear feature in meters >21 gslnc250# 4 5 B - Internal id number >25 gslnc250-ID 4 5 B - Internal id number Map Unit Delineations are closed polygons that are generally geographic mixtures of groups of soils or soils and nonsoil areas. The map unit ID uniquely identifies each closed delineation, map unit. Each map unit ID is linked to a map unit name. The map unit ID is also the key for linking information in the Map Unit Interpretations Record tables. The map units described below exist as text files, and can be obtained with the digital file at no extra charge from CGIA. Map Unit Delineations are described by the Map Unit Interpretations Record data base. This attribute data base gives the proportionate extent of the component soils and the properties for each soil. The data base contains both estimated and measured data on the physical and chemical soil properties and soil interpretations for engineering, water management, recreation, agronomic, woodland, range and wildlife uses of the soil. The Soil Map Unit Interpretations Record data base consist of the following relational tables: codes (data base codes) - stores information on all codes used in the data base comp (map unit component) - stores information which will apply to a specific component of a soil map unit compyld (component crop yield) - stores crop yield information for soil map unit components forest (forest understory) - stores information for plant cover as forest understory for soil map unit components interp (interpretation) - stores soil interpretation ratings (both limitation ratings and suitability ratings) to soil map unit components layer (soil layer) - stores characteristics which apply to soil layers for soil map unit components mapunit (map unit) - stores information which applies to all components of a soil map unit plantcom (plant composition) - stores plant symbols and percent of plant composition associated with components of soil map units (CGIA does not have) plantnm (plant name) - stores the common and scientific names for plants used in the data base rsprod (range site production) - stores range site production information for soil map unit components (CGIA does not have) taxclass (taxonomic classification) - stores the taxonomic classification for soils in the data base windbrk (windbreak) - stores information on recommended windbreak plants for soil map unit components wlhabit (wildlife habitat) - stores wildlife habitat information for soil map unit components woodland (woodland) - store information on common indicator trees for soil map unit components woodmgt (woodland management) - stores woodland management information for soil map unit components yldunits (yield units) - stores crop names and the units used to measure yield
U.S. Department of Agriculture. 1975. Soil Taxonomy: A basic system of soil classification for making and interpreting soil surveys. Soil Conserv. Serv., U.S. Dep. Agric. Handb. 436. U.S. Department of Agriculture. 1992. Keys to Soil Taxonomy. SMSS Technical Monograph No. 19. Soil Surv. Staff, Soil Conserv. Serv. U.S. Department of Agriculture. 1993. National Soil Survey Handbook, title 430-VI. Soil Surv. Staff, Soil Conserv. Serv. U.S. Department of Agriculture. 1993. Soil Survey Manual. Soil Surv. Staff, U.S. Dep. Agric. Handbook 18. U.S. Department of Agriculture. 1993. National Soil Survey Handbook, title 430-VI. Soil Surv. Staff, Soil Conserv. Serv. U.S. Department of Agriculture. 1994. State Soil Geographic (STATSGO) Data Base: Data use information. Soil Conserv. Serv. U.S. Department of Agriculture. State Soil Survey Database Data Dictionary. Soil Conserv. Serv.
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NCCGIA is charged with the development and maintenance of the State's corporate geographic database and, in cooperation with other mapping organizations, is committed to offering its users accurate, useful, and current information about the state. Although every effort has been made to ensure the accuracy of information, errors and conditions originating from physical sources used to develop the corporate database may be reflected in the data supplied. The client must be aware of data conditions and bear responsibility for the appropriate use of the information with respect to possible errors, original map scale, collection methodology, currency of data, and other conditions specific to certain data. NCCGIA does not support secondary distribution of this data. The use of trade names or commercial products does not constitute their endorsement by the NCCGIA or North Carolina State Government.
Data creation and large data analysis jobs contact Database Administration P:(919)733-2090. All data is available through standard ordering procedures on a cost recovery basis.
301 North Wilmington Street, Suite 700
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