Logical_Consistency_Report:
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 are free of gaps. The tests of logical
consistency are performed using vendor software. 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). Edge locations generally do
not deviate from centerline to centerline by more than 0.01 inch.
The Soil Survey of Erie County, Pennsylvania is edge matched to
the adjacent SSURGO (Soil SURvey GeOgraphic) certified Soil Surveys
of Ashtabula County, Ohio, Chautauqua County, New York, Crawford County,
Pennsylvania and Warren and Forest Counties, Pennsylvania.
The feature edges (mapping unit boundaries) match those in the adjacent
soil surveys. The descriptive attributes and the feature labels do not
match exactly.
The soil survey boundary for Erie County matches the soil
survey boundaries of the adjacent certified soil surveys.
Completeness_Report:
A map unit is a collection of areas defined and named in terms of
their soil components or miscellaneous areas or both. Each map
unit differs in some respect from all others in a survey area and
each map unit has a symbol that uniquely identifies the map unit
on a soil map. Each individual area, point, or line so identified
on the map is a delineation.
Soil Scientists identify small areas of soils or miscellaneous 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.
A map unit has specified kinds of soils or miscellaneous areas
(map unit components), each with a designated range in
proportionate extent. Map units include one or more kinds of soil
or miscellaneous area. Miscellaneous areas are areas that have little
or no recognizable soil.
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, NRCS; Agricultural Handbook 436, Soil Taxonomy, 1995,
USDA, NRCS; and all Amendments; Keys to Soil Taxonomy,
(current issue) USDA, NRCS; National Soil Survey
Handbook, title 430-VI,(current issue) USDA, NRCS.
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 use a single name from the
dominant component in the map unit. Dissimilar components are
minor in extent. The soil component in a consociation may be
identified at any taxonomic level. Soil series is the lowest
taxonomic level. A consociation that is named as a miscellaneous
area is dominantly that kind of area and minor components do not
significantly affect the use of the map unit. 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 consist
of two or more dissimilar components that occur in a regularly
repeating pattern. The total amount of other dissimilar components
is minor extent. The following arbitrary rule determines whether
complex or association is used in the name. The major components
of an association can be separated at the scale of mapping. In
either case, because the major components are sufficiently different
in morphology or behavior, the map unit cannot be called a
consociation. In each delineation of 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 are not consistently associated
geographically and, therefore, do not always occur together in
the same map delineation. These components are included in the
same named map unit because their use and management are the same
or very similar for common uses. Generally they are grouped together
because some common feature, such as steepness, stoniness, or
flooding, determines their use and management. If two or more
additional map units would serve no useful purpose, they may be
included in the same unit. Each delineation has at least one of the
major components, and some may have all of them. The same principles
regarding the proportion of minor components that apply to
consociations also apply to undifferentiated groups. The same
principles regarding proportion of inclusion 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 5 acres.