STATSGO Soils

GEODATASET NAME: SCA_STGOMUA83

IDENTIFICATION INFORMATION

Description:
    STATSGO soil map units and supporting attribute data for the 
    Southern California Pilot Study Area 
Abstract:
    Derived from 1:250,000-scale NRCS STATSGO soils coverage for the 
    U.S.
Data Type:
    Coverage, polygon
Raw Data Originator:
    USDA Natural Resources Conservation Service
    National Cartography and GIS Center
    P.O. Box 6567
    Fort Worth, TX 76115
Data Processor:
    Rick Van Remortel
    Lockheed Martin Environmental Services
    1050 E. Flamingo Road, Suite E120
    Las Vegas, NV 89119
    (702)897-3295
    rvanremo@lmepo.com
Data Provider:
    Dan Heggem
    U.S. Environmental Protection Agency NERL
    P.O. Box 93478
    Las Vegas, NV 89193-3478
    (702)798-2278
    heggem.daniel@epa.gov
Keywords:
    Southern California, watershed, soils, STATSGO
Version:
    N/A
Status:
    Interim
Revision Number:
    0
Series Name:                    
Online Link (URL):              
Time Period of Content:         
    From Dec. 1994 revision        
Use Constraints:                
    This coverage contains uncertainty specific to given locations on landscapes,
    so users should exercise caution when applying results to local situations.
    STATSGO is a state-level database and, as such, the specific attribute value 
    at a given point on the landscape cannot be known with certainty because the 
    distribution of soil components within each map unit is variable across a 
    state.  Finer resolution data can be derived from the SSURGO database (for 
    soil survey areas) where such data have been released by NRCS.  However, 
    SSURGO data only has improved resolution and still is not point-specific.  
    Caution must be exercised with the interpretations drawn from STATSGO and 
    SSURGO applications.  The present version of this coverage should be 
    considered Draft, for internal use only at this time.
Purpose:
    Southern California data browser
Date of metadata entry/update:
    1/22/2002
 
No Publication Information Available
No File Security Information Available
  
DATA QUALITY INFORMATION
 
Cloud Cover:
    Not applicable
Software:
    Arc/Info 7.2.1 Patch 2
Operating System:
    Unix Sun Solaris 2.7
Path Name:
    /gis/wemap/sca/soil
Logical Consistency Report:
    Not presently available
Completeness Report:
    Not presently available
Horizontal Positional Accuracy:
    Not presently available
Vertical Positional Accuracy:
    Not presently available
Attribute Accuracy:
    Not presently available
Procedures:
    The required Albers NAD27 state-level coverage(s) were copied from the 
    U.S. STATSGO workspace, and were mapjoined (where necessary), reprojected 
    to the study area projection, and then rebuilt and clipped to the study 
    area boundary. All required state-level Info attribute files were copied 
    from the U.S. STATSGO workspace and, using the coverage name, base files were
    created to hold the appended state Info attribute data.
Reviews Applied to Data
    Lockheed Martin Environmental Services internal review
Related Spatial Data Files:
    All geodatasets with sca_ prefix.
Other References Cited:  
Notes:
Update Frequency:
    As needed
 
SPATIAL REFERENCE INFORMATION

             Description of DOUBLE precision coverage sca_stgomua83
 
                                FEATURE CLASSES
 
                                    Number of  Attribute     Spatial
Feature Class          Subclass     Features   data (bytes)  Index?   Topology?
-------------          --------     ---------  ------------  -------  ---------
ARCS                                     1239
POLYGONS                                  433        32               Yes
NODES                                     851
ANNOTATIONS             (blank)             0
REGIONS                   WATER             1        24               Yes
 
                               SECONDARY FEATURES
 
Tics                                     1343
Arc Segments                            67843
Polygon Labels                            432
 
                                   TOLERANCES
 
Fuzzy   =                 0.000 V          Dangle  =                 0.000 N
 
                               COVERAGE BOUNDARY
 
Xmin =              -357521.759            Xmax =                46679.147
Ymin =              3399106.105            Ymax =              3658716.000
 
                                     STATUS
 
The coverage has not been Edited since the last BUILD or CLEAN.
 
                          COORDINATE SYSTEM DESCRIPTION
 
Projection               ALBERS
Datum                     NAD83
Units                    METERS             Spheroid                GRS1980
Parameters:
1st standard parallel                                   33 15  0.000
2nd standard parallel                                   40 15  0.000
central meridian                                       -116 45  0.00
latitude of projection's origin                          0  0  0.000
false easting (meters)                                       0.00000
false northing (meters)                                      0.00000

 
ENTITY AND ATTRIBUTE INFORMATION
Annotation Name:

FILE LISTING FOR: SCA_STGOMUA83

 TYPE NAME                            INTERNAL NAME    NO. RECS LENGTH EXTERNL
------------------------------------------------------------------------------
  DF  SCA_STGOMUA83.TIC                 ARC0026DAT        1343      20    XX
  DF  SCA_STGOMUA83.PATWATER            ARC0027DAT           1      24    XX
  DF  SCA_STGOMUA83.BND                 ARC0028DAT           1      32    XX
  DF  SCA_STGOMUA83.PAT                 ARC0029DAT         433      32    XX
  DF  SCA_STGOMUA83.COMP                ARC0030DAT        9898     292
  DF  SCA_STGOMUA83.COMPYLD             ARC0031DAT       11098      60
  DF  SCA_STGOMUA83.FOREST              ARC0032DAT       18296      24
  DF  SCA_STGOMUA83.INTERP              ARC0050DAT      256447      24
  DF  SCA_STGOMUA83.LAYER               ARC0051DAT       31247     244
  DF  SCA_STGOMUA83.MAPUNIT             ARC0052DAT         703     142
  DF  SCA_STGOMUA83.PLANTCOM            ARC0053DAT       25183      24
  DF  SCA_STGOMUA83.PLANTNM             ARC0054DAT         833      98
  DF  SCA_STGOMUA83.RSPROD              ARC0055DAT        2896      88
  DF  SCA_STGOMUA83.TAXCLASS            ARC0056DAT        1139     164
  DF  SCA_STGOMUA83.WINDBRK             ARC0057DAT        7945      24
  DF  SCA_STGOMUA83.WLHABIT             ARC0058DAT        9044     122
  DF  SCA_STGOMUA83.WOODLAND            ARC0059DAT        7638      28
  DF  SCA_STGOMUA83.WOODMGT             ARC0060DAT        2210      58
  DF  SCA_STGOMUA83.YLDUNITS            ARC0061DAT         226      40
  DF  SCA_STGOMUA83.S5_LAYER            ARC0062DAT       31247     298
  DF  SCA_STGOMUA83.S5_COMP             ARC0063DAT        9898     152

 
METADATA REFERENCE SECTION
 
FGDC Content Standards for Digital Geospatial Metadata
FGDC Standards Version 6/98 / metadata.aml ver. 1.3 5/21/99

SUPPLEMENTAL METADATA (where available)

Overview
	STATSGO was compiled for each state and designed primarily for 
regional, multi-state, river basin, state and multi-county resource 
planning, management, and monitoring.  STATSGO data are not sufficiently 
detailed to make interpretations at the county level.  In most areas, 
STATSGO maps were compiled by generalizing more detailed SSURGO maps.  
Where more detailed soil survey maps were not available, data on geology, 
topography, vegetation, and climate were assembled, together with LANDSAT 
images.  Soils of like areas were studied, and probable classification and 
extent of soils was determined.  STATSGO map units are combinations of areas 
on the more detailed soils maps.  Attributes of STATSGO map units are 
statistical summaries of attributes from all the component soils used to 
characterize an entire map unit.  Consequently, each map unit can have 
multiple components (maximum of 21) and each component can have multiple 
layers (maximum of six). The soils component attribute table maintains 
60 variables for each soil component.  The layer table maintains 28 variables 
for each soil component layer.  In addition to the soil tables (component
and layer), STATSGO contains ten interpretive data tables and three lookup 
tables for use with the spatial database.
	STATSGO includes a complex variety of soil and soil-related data on 
a state-wide basis.  The challenge in creating a tool to access this database 
is to make access efficient and easy-to-use within the constraints of the 
database design.  The STATSGO multiple component and layer structure of the 
database makes its use with GIS complex.  The structure of STATSGO requires
linking map units and attribute tables through a many-to-many-to-many 
relationship.  That is, there are many non-contiguous polygons in each STATSGO 
map unit. Texas, for example, has map units with as many as 45 discrete polygons, 
and one map unit in Alaska has 90 polygons.  Individual state component tables 
are related to map units by map unit identifier (MUID).  There are as many as
21 soil components for each map unit.  The layer table is related to the 
component table by unique component identifiers made up of a MUID and sequence 
number (SEQNUM).  Sequence numbers represent soil layers in each component. 
There are as many as 6 soil layers for each soil component. 
	The STATSGO map unit is the smallest spatial entity that can be queried 
and mapped while remaining consistent with the database. Map units are comprised 
of up to 21 components of varying areas that contribute to the total area of the 
map unit.  The areal/spatial composition of the map unit was derived from a 
statistical analysis of  transects across detailed soil survey maps.  The area of 
the map unit occupied by each component is proportional to the length of the 
transects containing that component.  The area occupied by each component is
represented as a percent of the map unit, but there is no specific location of 
individual components within any polygon.  Thus, the percentage of each soil 
component area in the map unit must be used to characterize the map unit.
	In order to make STATSGO soils data compatible with the Arc/Info data 
model, the structure of the database can be modified include an intermediate 
key file and an accumulation table to replace the many-to-many relationships 
with one-to-many relationships.  The key file contains the component percentages 
for each map unit.

Narrative
	The U.S. Department of Agriculture (USDA) Natural Resources 
Conservation Service (NRCS), formerly Soil Conservation Service (SCS), leads 
National Cooperative Soil Survey (NCSS) and is responsible for collecting, 
storing, maintaining, and distributing soil survey information for privately 
owned lands in the United States.  The NRCS established three soil geographic 
data bases representing kinds of soil maps.  The maps are produced from 
different intensities and scales of mapping. Each data base has a common link 
to an attribute data file for each map unit component. The Soil Interpretations 
Record (SIR) data base provides attribute data for each geographic data base.  
	The three soil geographic data bases are the Soil Survey Geographic 
(SSURGO) data base, the State Soil Geographic (STATSGO) data base, and the 
National Soil Geographic (NATSGO) data base. Components of map units in each 
data base are generally phases of soil series that enable the most precise 
interpretation. Interpretations are displayed differently for each geographic 
data base to be consistent with differing levels of detail. The SIR data base 
contains physical and chemical soil properties for approximately 18,000 soil 
series recognized in the United States.  
	The SSURGO data base provides the most detailed level of information 
and was designed primarily for farm and ranch, landowner/user, township, county, 
or parish natural resource planning  and management. Using the soil attributes, 
this data base serves as an excellent source for determining erodible areas and 
developing erosion control practices, reviewing site development proposals and 
land use potential, making land use assessments, and identifying potential 
wetlands and sand and gravel aquifer areas.  Using NCSS mapping standards, 
soil maps in the SSURGO data base are made using field methods. Surveyors 
observe soils along delineation boundaries and determine map unit composition 
by field traverses and transects.  Aerial photographs are interpreted and 
used as the field map base. Maps are made at scales ranging from 1:12,000 to 
1:63,360. Typically scales are 1:15,840, 1:20,000, or 1:24,000. The maps, along 
with comprehensive descriptions, produce an attribute and spatial data base for 
NCSS publications.  Line segments (vectors) are digitized in accordance with 
specifications and standards established by the NRCS for duplicating the 
original soil survey map. The mapping bases are normally orthophotoquads, 
and digitizing is performed by NRCS, by contractors, or by cooperating Federal, 
State, and local governments. Data for the SSURGO data base are collected and 
archived in 7.5 minute topographic quadrangle units and distributed as a 
complete coverage for a soil survey area usually consisting of 10 or more 
quadrangle units. The adjoining 7.5 minute units are matched within the survey 
areas.
	The STATSGO data base was designed primarily for regional, multistate, 
river basin, State, and multicounty resource planning, management, and 
monitoring.  STATSGO data are not detailed enough to make interpretations 
at a county level.  Soil maps for STATSGO are compiled by generalizing more 
detailed (SSURGO) 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.  Using 
the United States Geological Survey's (USGS) 1:250,000 scale, 1- by 2-degree 
quadrangle series as a map base, the soil data are digitized by line segment 
(vector) method to comply with national guidelines and standards.  Data for 
the STATSGO data base are collected in 1- by 2-degree topographic quadrangle 
units and merged and distributed as statewide coverages. Features are edge 
matched between states. The map unit composition and the proportionate 
extent of the map unit components also match between states.
	The NATSGO data base is used primarily for national and regional 
resource appraisal, planning, and monitoring. The boundaries of the major 
land resource areas (MLRA) and regions were used to form the NATSGO data 
base [6]. The MLRA boundaries were developed primarily from State general 
soil maps.  Map unit composition for NATSGO was determined by sampling done 
as part of the 1982 National Resources Inventory [7]. Sample data were 
expanded for the MLRAs, with sample design being statistically significant 
to State parts of the MLRAs.  The NATSGO map was compiled on an NRCS-adapted 
version of the 1970 Bureau of Census automated State and county map data 
base and it was digitized from the USGS 1:5,000,000 scale U.S. base map.
	This document describes the STATSGO data, which provide national 
coverage at a scale of 1:250,000, except for Alaska, which is at a scale 
of 1:2,000,000.  A soil map in a soil survey is a representation of soil 
patterns in a landscape. The scale of the map and the complexity of the 
soil patterns determine what can be shown on the soil map. In designing 
soil surveys, the projected uses of the survey and the complexity of the 
soil patterns largely determine the scale of the soil map [4].  When using 
soil maps, remember that scale, accuracy, and detail are not synonymous.  
Scale is the relationship between corresponding distance on a map and the 
actual distance on the ground. Accuracy is the degree or precision with 
which map information is obtained, measured, and recorded, and detail is 
the amount of information shown.
	Map scale, accuracy, and detail are interrelated. A large-scale map 
is not necessarily more accurate or more detailed than a small-scale map; 
however, it generally shows more detail than a small-scale map. Soil maps 
are made by using field investigation methods. The accuracy of the maps is 
determined by many factors, including the complexity of the soils, design 
of the soil map units, intensity of field observations and data collection, 
and skills of the mapper.  A soil map at 1:250,000 scale should not be used 
to locate soils for intensive land uses, such as determining suitability for 
house lots. It is useful for understanding the soil resources and for planning 
broad use in a State or region. A soil map at 1:20,000 scale is useful in 
understanding and planning the soil resources of fields, farms, and 
communities,  but it is not useful for planning small (less than 1 acre) 
research plots. In many places the pattern of soils is very complex, and in 
some places soils grade imperceptibly to others. Because of this, soil 
delineations, even on large-scale maps, are not homogeneous or pure; thus, 
onsite investigations are needed to determine, for example, the suitability 
of a plot for a septic tank installation when using a soil map at scale of 
1:20,000.  The common practice of enlarging soil maps does not result in more 
detailed or accurate maps. Soil survey maps enlarged to 1:12,000 scale from 
1:20,000 scale are no more accurate or detailed than the original 1:20,000 map.  
Many times the information on soil maps is transferred to other base maps at 
different scales, which diminishes the new map's accuracy, especially if the 
base map is not planimetrically correct.
	Soil interpretive maps for specific uses are commonly made from the 
soil maps. These kinds of maps are single purpose and have the same credibility 
and limitations as the soil maps from which they are made.  Recognizing the 
different kinds of soil maps, knowing their merits and limitations, and 
understanding the relationship of map scale, accuracy, and detail are important.
In a detailed SSURGO soil map, each map unit is usually represented by a single 
soil component, typically a soil series phase [5]. Some SSURGO map units may 
have up to three named components. An interpretive map is normally made by 
classifying each unit according to the set of soil properties for a single 
component. In contrast, each map unit on a STATSGO map contains up to 21 
discrete components for which there are attribute data, but there is no 
visible distinction as to the location of these components within the 
delineation. Thus, to present information on an attribute, a series of maps 
must be used to portray the more complex set of available information.  The 
legend for STATSGO interpretive maps commonly shows the percentage of the map 
unit that meets a criterion or criteria. Caution must be used in evaluating 
the statistics presented in such a legend. Percentage ranges given represent 
all delineations in that class and do not represent an individual STATSGO 
delineation. Percentages do not statistically represent a subset of the 
delineation such as a county portion. They also do not represent the areas 
of the soil components that satisfy the criterion. However, the area of each 
map unit component is recorded in the data base and can be used to produce 
a table, even though the components cannot be displayed directly on the map.
	When STATSGO data are overlayed with other data, 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. It is incorrect to 
assign  land use attributes to the soil components by multiplying the 
proportions of soil components by the proportions of land uses. 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.

Map Unit Delineations
	Approximate minimum area delineated is 625 hectares (1,544 acres), 
represented on a map of 1:250,000 scale by an area appropriately 1 cm by 
1 cm (0.4 inch by 0.4 inch). Linear delineations should not be less than 
0.5 cm (0.2 inch) in width.  The number of delineations per 1:250,000 
quadrangle should range from 100 to 200, but a range of up to 400 is allowed.  
Delineations depict the dominant soils making up the landscape.  Other dissimilar 
soils, too small to be delineated, are present within a delineation.  Map unit 
delineations must join at State boundaries and composition of map 
units must be coordinated across State boundaries, not only in the identity, 
but also in the relative extent of each component. All component phase 
criteria are to join across State boundaries.

	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.
Components
	Map units are a combination of associated phases of soil series.  
Information about map units includes reliable estimates of the components 
and the percentage and method by which the composition is determined. 
Composition is determined by transecting representative segments of map 
units in published or unpublished soil surveys and documenting component 
composition or by using acreage data in the map unit use file. Transects 
may be observed in the field; however, it is more likely that they will be
located and examined on soil survey field sheets or in published soil surveys. 

Attribute Tables
	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
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
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