U.S. Department of Agriculture, Natural Resources Conservation Service, 20030624, Soil Survey Geographic (SSURGO) database for Napa County, California: U.S. Department of Agriculture, Natural Resources Conservation Service, Fort Worth, Texas.Online Links:
This is a Vector data set.
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 1.8288
Ordinates (y-coordinates) are specified to the nearest 1.8288
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.0.
The flattening of the ellipsoid used is 1/298.257.
Formal codeset | |
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Codeset Name: | Classification and Correlation of the Soils of Napa County, California |
Codeset Source: | U.S. Department of Agriculture, Natural Resources Conservation Service |
530 792 5640 (voice)
530 792 5794 (FAX)
SSURGO depicts information about the kinds and distribution of soils on the landscape. The soil map and data used in the SSURGO product were prepared by soil scientists as part of the National Cooperative Soil Survey.
U.S. Department of Agriculture, Soil Conservation Service, 1978, Soil Survey of Napa County, California: Government Printing Office, Washington, D.C..
U.S. Department of Agriculture, Natural Resources Conservation Service, unpublished material, publication negatives.
U.S. Department of Agriculture, Natural Resources Conservation Service, unpublished material, publication positives.
U.S. Geological Survey, 1954, multiple 7.5 minute topographic quadrangles.
U.S. Department of Agriculture, Natural Resources Conservation Service, unpublished material, DLG-3 files.
U.S. Department of Agriculture, Natural Resources Conservation Service, 1999, Soil Survey Geographic (SSURGO) database for Napa County, California: U.S. Department of Agriculture, Natural Resources Conservation Service National Cartography and Geospatial Center, Ft. Worth, Texas.
U.S. Department of Agriculture, Natural Resources Conservation Service, unpublished material, ARC EXCHANGE files for the soil survey of Napa County, California.
U.S. Department of Agriculture, Natural Resources Conservation Service, unpublished material, MrSID compressed image for Napa County, California.
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
U.S. Department of Agriculture, Soil Conservation Service, 1978, Soil Survey of Napa County, California.
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 amendment(s).
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 soil boundaries and special soil features locations 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, on long gently sloping landscapes the transition occurs gradually over many feet. Where landscapes change abruptly from steep to level, the transition will be very narrow. Soil delineation boundaries and special soil features generally were digitized within 0.01 inch of their locations on the digitizing source. The digital map elements are edge matched between data sets. The data along each quadrangle edge are matched against the data for the adjacent quadrangle. Edge locations generally do not deviate from centerline to centerline by more than 0.01 inch.
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 or more components.
Soil scientists identify small areas of soils or miscellaneous (nonsoil) areas that have properties and behavior significantly different than the named soils in the surrounding map unit. These minor components may be indicated as special features. If they have a minimal effect on use and management, or could not be precisely located, they may not be indicated on the map.
Specific National Cooperative Soil Survey standards and procedures were used in the classification of soils, design and name of map units, and location of special soil features. These standards are outlined in Agricultural Handbook 18, Soil Survey Manual, 1993, USDA, SCS; Agricultural Handbook 436, Soil Taxonomy, Soil Survey Staff, 1975, USDA, SCS; and all Amendments; Keys to Soil Taxonomy, Soil Survey Staff, (current issue); National Soil Survey Handbook, title 430-VI, (current issue).
The actual composition and interpretive purity of the map unit delineations were based on data collected by scientists during the course of preparing the soil maps. Adherence to National Cooperative Soil Survey standards and procedures is based on peer review, quality control, and quality assurance. Quality control is outlined in the memorandum of understanding for the soil survey area and in documents that reside with the Natural Resources Conservation Service state soil scientist. Four kinds of map units are used in soil surveys: consociations, complexes, associations, and undifferentiated groups.
Consociations - Consociations are named for the dominant soil. In a consociation, delineated areas are dominated by a single soil taxon and similar soils. At least one half of the pedons in each delineation are of the same soil component so similar to the named soil that major interpretations are not affected significantly. The total amount of dissimilar inclusions of other components in a map unit generally does not exceed about 15 percent if limiting and 25 percent if nonlimiting. A single component of a dissimilar limiting inclusion generally does not exceed 10 percent if very contrasting.
Complexes and associations - Complexes and associations are named for two or more dissimilar components with the dominant component listed first. They occur in a regularly repeating pattern. The major components of a complex cannot be mapped separately at a scale of about 1:24,000. The major components of an association can be separated at a scale of about 1:24,000. In each delineation of either a complex or an association, each major component is normally present, though their proportions may vary appreciably from one delineation to another. The total amount of inclusions in a map unit that are dissimilar to any of the major components does not exceed 15 percent if limiting and 25 percent if nonlimiting. A single kind of dissimilar limiting inclusion usually does not exceed 10 percent.
Undifferentiated groups - Undifferentiated groups consist of two or more components that do not always occur together in the same delineation, but are included in the same named map unit because use and management are the same or similar for common uses. Every delineation has at least one of the major components and some may have all of them. The same principles regarding proportion of inclusions apply to undifferentiated groups as to consociations.
Minimum documentation consists of three complete soil profile descriptions that are collected for each soil added to the legend, one additional per 3,000 acres mapped; three 10 observation transects for each map unit, one additional 10 point transect per 3,000 acres.
A defined standard or level of confidence in the interpretive purity of the map unit delineations is attained by adjusting the kind and intensity of field investigations. Field investigations and data collection are carried out in sufficient detail to name map units and to identify accurately and consistently areas of about 6 acres.
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 soil survey area and edge locations generally do not deviate from centerline to centerline by more than 0.01 inch. Quadrangles in this survey are joined to quadrangles in the Lake County, the Yolo County, the Solano County, and the Sonoma County, California soil survey areas.
Are there legal restrictions on access or use of the data?
- Access_Constraints: None
- Use_Constraints:
- The U.S. Department of Agriculture, Natural Resources Conservation Service, should be acknowledged as the data source in products derived from these data. This data set is not designed for use as a primary regulatory tool in permitting or citing decisions, but may be used as a reference source. This is public information and may be interpreted by organizations, agencies, units of government, or others based on needs; however, they are responsible for the appropriate application. Federal, State, or local regulatory bodies are not to reassign to the Natural Resources 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.
Photographic or digital enlargement 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. Digital data files are periodically updated. Files are dated, and users are responsible for obtaining the latest version of the data.
800 672 5559 (voice)
817 509 3469 (FAX)
Napa County, California SSURGO
Although these data have been processed successfully on a computer system at the U.S. Department of Agriculture, no warranty expressed or implied is made by the Agency regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. The U.S. Department of Agriculture will warrant the delivery of this product in computer readable format, and will offer appropriate adjustment of credit when the product is determined unreadable by correctly adjusted computer input peripherals, or when the physical medium is delivered in damaged condition. Request for adjustment of credit must be made within 90 days from the date of this shipment from the ordering site. The U.S. Department of Agriculture, nor any of its agencies are liable for misuse of the data, for damage, for transmission of viruses, or for computer contamination through the distribution of these data sets. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.)
Data format: | spatial in format ARC/INFO coverage Size: 11.4 |
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Media you can order: |
CD-ROM
(format ISO 9660 Level 1)
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Data format: | spatial in format ARCE Size: 26.1 |
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Media you can order: |
CD-ROM
(format ISO 9660 Level 1)
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Data format: | spatial in format ArcView shapefile Size: 41.8 |
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Media you can order: |
CD-ROM
(format ISO 9660 Level 1)
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Data format: | spatial and keys in format DLG Optional Size: 7.5 |
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Media you can order: |
CD-ROM
(format ISO 9660 Level 1)
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Data format: | keys and attributes in format ASCII Size: 34.2 |
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Media you can order: |
CD-ROM
(format ISO 9660 Level 1)
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The charge is $50 for a CD-ROM that contains one or more data sets. A data set is one soil survey area in full quadrangle format and includes both spatial and attribute data.
Call or write to organizations listed under Distributor. Spatial line data and locations of special feature symbols are in DLG-3 optional format, ARC/INFO coverage and export formats, and ArcView shapefile format. Digital line graph files contain major and minor code pairs in area and line records. A conversion legend is provided for each digital line graph file. Soil map symbols and special feature labels are available in a companion ASCII attribute file. The National Soil Information System attribute soil data are available in variable length, pipe delimited, ASCII file format.
10 working days
530 792 5640 (voice)
530 792 5794 (FAX)