FGDC Document Number FGDC-STD-015-2009

Wetlands Mapping Standard

FGDC Wetlands Subcommittee

July 2009
Federal Geographic Data Committee FGDC Document Number FGDC-STD-015-2009

Wetlands Mapping Standard

ii

Federal Geographic Data Committee

Established by Office of Management and Budget Circular A-16, the Federal Geographic 

Data Committee (FGDC) promotes the coordinated development, use, sharing, and 

dissemination of geographic data. 

The FGDC is composed of representatives from the Departments of Agriculture, 

Commerce, Defense, Education, Energy, Health and Human Services, Homeland 

Security, Housing and Urban Development, the Interior, Justice, Labor, State, and 

Transportation, the Treasury, and Veteran Affairs; the Environmental Protection Agency; 

the Federal Communications Commission; the General Services Administration; the 

Library of Congress; the National Aeronautics and Space Administration; the National 

Archives and Records Administration; the National Science Foundation; the Nuclear 

Regulatory Commission; the Office of Personnel Management; the Small Business 

Administration; the Smithsonian Institution; the Social Security Administration; the 

Tennessee Valley Authority; and the U.S. Agency for International Development. 

Additional Federal agencies participate on FGDC subcommittees and working groups. 

The Department of the Interior chairs the committee. 

FGDC subcommittees work on issues related to data categories coordinated under the 

circular. Subcommittees establish and implement standards for data content, quality, and 

transfer; encourage the exchange of information and the transfer of data; and organize the 

collection of geographic data to reduce duplication of effort. Working groups are 

established for issues that transcend data categories. 

For more information about the committee, or to be added to the committee's newsletter 

mailing list, please contact: 

Federal Geographic Data Committee Secretariat 

c/o U.S. Geological Survey 

590 National Center 

Reston, Virginia 22092

Facsimile: (703) 648-5755 

Internet (electronic mail): fgdc@usgs.gov 

World Wide Web: http://www.fgdc.gov
Federal Geographic Data Committee FGDC Document Number FGDC-STD-015-2009

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CONTENTS

Page

1 Introduction ............................................................................................................... 1

1.1 Background.......................................................................................................... 1

1.2 Objectives ............................................................................................................ 2

1.3 Scope.................................................................................................................... 2

1.4 Applicability ........................................................................................................ 5

1.5 FGDC Standards and Other Related Practices..................................................... 5

1.6 Standard Development Procedures and Representation ...................................... 7

1.7 Maintenance Authority ........................................................................................ 7

2 FGDC requirements and Quality components....................................................... 7

2.1 Imagery ................................................................................................................ 7

2.1.1 Source Imagery ........................................................................................... 8

2.1.2 Base Imagery .............................................................................................. 9

2.2 Classification........................................................................................................ 9

2.3 Accuracy ............................................................................................................ 10

2.3.1 Target Mapping Unit and Producer’s Accuracy ....................................... 11

2.3.2 Horizontal Accuracy ................................................................................. 12

2.4 Data Verification................................................................................................ 13

2.4.1 Logical Consistency.................................................................................. 13

2.4.2 Edge Matching.......................................................................................... 14

2.4.3 Attribute Validity...................................................................................... 14

2.5 Datum and Projection ........................................................................................ 15

2.6 Metadata............................................................................................................. 15

2.7 FWS Coordination and Quality Control ............................................................ 15

References 17

Appendix A: Attributes for Wetland Classification (Normative) ............................ 19

Appendix B: Attributes for LLWW (for Landscape, Landform, Water Flow path, 

and Waterbody Type) (Informative).................................................... 23

Appendix C: Definitions (Informative)....................................................................... 31

FIGURES

Figure 1a: Wetlands and Deepwater Habitats Classification............................................ 21

Figure 1b: Wetlands and Deepwater Habitats Classification ........................................... 22
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TABLES

Page

Table 1. Spatial Resolution Requirements of Source Imagery.......................................... 8

Table 2. Spatial Resolution Requirements of Base Imagery ............................................. 9

Table 3. Classification Levels Required Based on Habitat Type .................................... 10

Table 4. TMU and PA Requirements .............................................................................. 12

Table 5. Horizontal RMSE Accuracy Requirements....................................................... 13
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1 INTRODUCTION

1.1 Background

The U.S. Fish and Wildlife Service (FWS) has had the responsibility for 

mapping wetlands in the United States. Those map products are currently 

held in the Fish and Wildlife Service Wetland Database (sometimes 

referred to as the National Wetlands Inventory or NWI). As time has 

passed, more local, state and non-governmental organizations have 

become interested in mapping wetlands, and at a more refined scale than 

has been available from the Service’s Wetland Database. It has become 

increasingly important to have consistency and to develop a wetlands 

mapping standard that everyone can use to map and share wetlands data in 

a digital format. It is highly desirable to be able to reprocess wetlands 

data from the Service’s Wetland Database to support multiple mapping 

applications and digital products. It is also important for wetland data to 

be “compatible/complementary” with other water data, such as the 

features represented in the National Hydrography Dataset (NHD), so that 

wetlands can be considered in a more holistic environmental context, 

whether at the watershed, ecosystem, or regional level. 

In early wetlands inventory mapping, the intended end-products were 

primarily paper-based maps, and small wetland features were represented 

as points. These points were an artifact of the scale limitations of the 

cartographic technology used at the time. As technology progressed, such 

geographic data were stored as polygons and lines. The use of modern 

digital technology and on-screen mapping of wetlands allows 

interpretation to be done in much finer detail. Features previously 

represented as points and lines can now be delineated as polygons. 

Increasingly, such finer-detail digital wetlands map products are needed 

(instead of the traditional paper-based maps), to allow for comparison with 

other maps and data, execution of spatial analyses, and other data 

processing. 

The Wetlands Geodatabase, which houses all FWS digital geospatial 

wetlands data, including digital data contributed by outside cooperators, 

forms the Wetlands Spatial Data Layer of the National Spatial Data 

Infrastructure (NSDI). A national standard is needed to facilitate inclusion 

of new wetlands data into the NSDI, as mandated by Office of 

Management and Budget Circular A-16 (Revised) August 19, 2002. This 

will support a consistent transition from traditional paper-based map 

products to technology-based mapping products, and increase sharing and 

multiple uses of the wetlands data. 
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1.2 Objectives

The objective of the Federal Geographic Data Committee’s (FGDC)

Wetlands Mapping Standard is to support the accurate mapping and 

classification of wetlands while ensuring mechanisms for their revision 

and update as directed under OMB Circular A-16 (Revised). This new 

FGDC Standard is designed to direct the current and future digital 

mapping of wetlands.

The current structure of the FWS Wetlands Geodatabase is a mosaic of 

best available wetlands data. The goal of the Federal Geographic Data 

Committees Standard is to improve the overall quality and consistency of 

new wetland data added to the FWS wetlands data layer. While this 

standard cannot change the FWS wetlands data produced prior to its 

implementation, the standard specifies a core set of data quality 

components necessary to add to the FWS wetlands data layer in a way that 

is consistent and supports multiple uses of the data, while meeting the 

requirements of the NSDI. The standard is based largely on the existing

standard used by U.S. Fish and Wildlife Service in support of the 

Service’s Wetland Database: Fish and Wildlife Service National 

Standards and Quality Components for Wetlands, Deepwater and Related 

Habitat Mapping.

The standard provides specification of the minimum data quality 

components for wetlands inventory mapping needed to support inclusion 

of the data into the NSDI, particularly when these activities are funded or 

conducted by the Federal government. The standard balances the burden 

on the end-user community with the need for consistency and documented 

quality of digital mapping products. Additionally, this standard is created 

to coordinate wetlands mapping with the NHD, a national geospatial

framework recognized by the FGDC. Although this standard is structured 

to be extensible over time, it is deliberately developed with a forwardlooking perspective to accommodate technology and map-scale 

enhancements that assure its long-term usability, and minimize the need 

for revisions and updates. 

1.3 Scope

The FGDC Wetlands Mapping Standard directs the incorporation of 

federally-funded wetlands data into the Wetlands Geodatabase (under 

direction of the FWS) and the Wetlands Data Layer of the NSDI. This 

standard provides minimum requirements and guidelines for wetlands 

inventory mapping. Specific cartographic, photogrammetric, and 

classification conventions where applicable, have been identified and are 
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represented by other Federal standards. Nothing in the standard precludes 

the use of ancillary or collateral data (such as soil data, Digital Elevation 

Models, LIDAR, radar, topographic maps, etc.) to enhance wetland 

mapping. In fact, these ancillary or collateral sources are often important 

in wetland mapping.

For activities which include wetlands inventory mapping as a subset, any 

new, updated or revised wetland mapping shall conform to this standard. 

More general mapping activities may use wetlands data from NSDI to 

incorporate the wetland subset rather than conducting new wetland 

mapping. Mapping activities of which wetlands may be a subset include,

but are not limited to:

Land Use Land Cover (LULC) classifications

Forest cover maps

Floodplains

Exemptions to the Standard

Circumstances for which this Standard does not apply, or for 

which portions of the technical requirements of the Standard may be 

waived, include the following:

1. Wetlands inventory mapping activities that are not federally-funded 

are strongly encouraged but not required, to comply with the FGDC 

Wetlands Mapping Standard. The NSDI will not incorporate noncompliant wetlands inventory data from any source except the FWS 

wetlands maps created prior to the implementation of this Standard 

(these pre-standard FWS wetland maps may be provided as scanned 

images only).

2. FWS wetlands mapping and other federally-funded projects that began 

prior to the Standard’s effective date. Also exempt are federallyfunded projects for which contract execution occurred prior to the 

Standard’s effective date, even if the actual work had not begun prior 

to that date. 

3. The Standard is designed to support polygonal wetland datasets and 

does not apply to plot/point transects, and linear datasets. While 

nothing in this standard precludes the capture of point or line data for 

referencing wetlands below the target mapping unit (TMU, see section 

2.3.1), only polygon features will be included in the FWS Wetlands 

Database.

4. The Standard is neither designed, nor intended, to support legal, 

regulatory, or jurisdictional analyses of wetland mapping products, nor 
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does it attempt to differentiate between regulatory and non-regulatory

wetlands.

5. Change detection efforts that seek to extrapolate the amount of change 

in wetland area, type, functionality, value, integrity or quality, from 

samples. An intermediate step in these change detection efforts may 

include mapping individual wetlands in sample plots; this Standard 

does not prevent Federal funding for this intermediate step. 

6. Marine and estuarine benthic habitat mapping is exempt because it 

currently necessitates the use of definitions and classifications which 

require different approaches than the FGDC Classification of Wetlands 

and Deepwater Habitats in the United States standard.

7. Maps and data developed for site-specific wetland studies for scientific 

research, environmental assessments (EAs) and environmental impact 

statements (EIS), and wetland determinations for regulatory purposes, 

when these site-specific activities necessitate the use of definitions and 

classifications which are incompatible with the FGDC wetland 

classification standard.

8. Mapping products when they are not developed primarily for wetland 

inventory mapping and classification. These types of data are useful as 

ancillary or collateral data for wetlands inventory mapping. For 

example: 

Deepwater substrate types

Vegetation types

Soil types (including hydric soil units)

Topography

Geology

Forest cover maps

Hydrography

Navigation or bathymetry

Submerged aquatic vegetation (SAV)

9. In order to ensure the “best available” data are included in the 

wetlands layer of the NSDI, a mechanism is needed to allow the 

incorporation of wetlands data that are not compliant with the FGDC

Wetlands Mapping Standard. Allowing extremely limited and welljustified inclusion of non-compliant data where data meeting the 

Standard does not yet exist may allow for comprehensive coverage of 

“best available” data more quickly, meeting the needs of many end 

users. An exemption from a specific minimum requirement in the 

Standard may be granted based on data quality, but not on cost. An 

authorized exemption or waiver from a specific minimum requirement 

in the Standard may be requested to incorporate non-compliant 

wetlands data. The official waiver form, instructions, and contact 

information are available from the FWS at 
Federal Geographic Data Committee FGDC Document Number FGDC-STD-015-2009

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http://www.fws.gov/wetlands/WetlandsLayer/WetlandsSubcommittee.html. 

The FWS is the final authority for approving or rejecting the waiver 

request. 

1.4 Applicability

This standard is intended for all Federal or federally-funded wetlands 

inventory mapping including those activities conducted by Federal 

agencies, states, and federally-recognized tribal entities, non-governmental 

organizations, universities, and others. Specifically, if Federal funding is 

used in support of wetlands inventory mapping activities, then use of this 

standard is mandatory. The adoption of the standard for all other wetlands 

inventory mapping efforts (non-federally funded) is strongly encouraged 

to maintain and expand the wetland layer of the NSDI. 

1.5 FGDC Standards and Other Related Practices

The following standards and applications are listed as core components to 

the FGDC Wetlands Mapping Standard effort. Some of these standards 

are included because the FGDC Wetlands Mapping Standard was 

developed in consideration and conformance with their requirements and 

intent. 

The related FGDC standards include:

Classification of Wetlands and Deepwater Habitats in the United 

States, FGDC-STD-004 

http://www.fws.gov/wetlands/_documents/gNSDI/ClassificationWetla

ndsDeepwaterHabitatsUS.pdf

Content Standard for Digital Geospatial Metadata (version 2.0) 

FGDC-STD-001-1998, http://www.fgdc.gov/metadata/geospatialmetadata-standards

Geospatial Positioning Accuracy Standards Part 3. National standard 

for spatial data accuracy. FGDC-STD-007.3-1998, 

http://www.fgdc.gov/standards/projects/FGDC-standardsprojects/accuracy/part3/chapter3

National Vegetation Classification Standard (Version 2), FGDC-STD005-2008

Soil Geographic Data Standard, FGDC-STD-006

Information Technology – Geographic Information Framework Data 

Content Standard, Part 5: Governmental unit and other geographic area 

boundaries, http://www.fgdc.gov/standards/projects/FGDC-standards-
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projects/framework-datastandard/GI_FrameworkDataStandard_Part5_GovernmentalUnitBoun

daries.pdf

Other related practices include:

Canadian Wetland Inventory maintained by Agriculture and AgriFood Canada (AAFC) at http://www.cwi-icth.ca/

National Hydrography Database (NHD) maintained by the USGS at 

http://nhd.usgs.gov/ 

Fish and Wildlife Service National Standards and Quality Components 

for Wetlands, Deepwater and Related Habitat Mapping, 

http://www.fws.gov/stand/standards/dl_wetlands_National%20Standar

ds.doc

Draft FGDC Riparian Standard maintained by FGDC at

http://www.fgdc.gov/standards/projects/FGDC-standardsprojects/riparian-mapping/index_html

Guidance for Benthic Habitat Mapping: An Aerial Photographic 

Approach maintained by the U.S. NOAA Coastal Services Center. 

Available for download at

http://www.csc.noaa.gov/benthic/mapping/pdf/bhmguide.pdf.

Coastal and Marine Ecological Classification Standard (CMECS)

developed for NOAA by NatureServe at 

http://csc.noaa.gov/benthic/funding/active.htm

RAMSAR Classification for Wetland Type maintained by Convention 

on Wetlands (Ramsar, Iran, 1971) at 

http://www.ramsar.org/ris/key_ris_types.htm

Primary Indicators Method. Tiner, R.W. 1993. The primary 

indicators method - a practical approach to wetland recognition and 

delineation in the United States. Wetlands 13(1): 50-64. (This method 

is typically used for verifying Service Wetland Database wetlands on 

the ground),

http://www.fws.gov/wetlands/_documents/gOther/PrimaryIndicatorsM

ethod.pdf

NatureServe’s Terrestrial Ecological System Classification

Comer, P., D. Faber-Langendoen, R. Evans, S. Gawler, C. Josse, G. 

Kittel, S. Menard, M. Pyne, M. Reid, K. Schulz, K. Snow, and J. 

Teague. 2003. Ecological Systems of the United States: A Working 

Classification of U.S. Terrestrial Systems. NatureServe, Arlington, 

Virginia.

http://www.natureserve.org/library/usEcologicalsystems.pdf
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1.6 Standard Development Procedures and Representation

Stakeholder representation from the Federal, State, and local government, 

non-profit, and private sectors was included in the development of this 

Standard to ensure that the end-user information requirements are 

reflected in the final product. Technical development of the content of this 

Standard began in June 2006 with a 3-day meeting of the workgroup 

comprised of members representing multiple Federal agencies and 

stakeholder groups. It was emphasized again that the Standard would 

benefit from a wide vetting process targeting diverse members of the enduser community. Technical refinement of the Standard occurred through 

the Spring of 2008 based on over 125 comments received through the 

Federal Register Notice process in late 2007.

 

The development of this Standard generated findings for minor revisions 

to other existing FGDC standards, including an expansion of the FGDC 

Wetlands and Deepwater Habitat Classification System; additional tools 

for handling and tracking wetland unique identifiers; and publishing new 

FGDC standards for related habitat types.

1.7 Maintenance Authority

The maintenance authority for the FGDC Wetlands Mapping Standard

resides with the Chair of the FGDC Wetland Subcommittee at the Fish and 

Wildlife Service. This workgroup recommends review of this Standard at 

five-year intervals. 

2 FGDC REQUIREMENTS AND QUALITY COMPONENTS

The sections below present the specifications for the technical components 

of the FGDC Wetlands Mapping Standard. To further the Information

Quality Act and conform to the FWS “Data Collection Standards for 

Mapping Wetland, Deepwater and Related Habitats”, a technically skilled 

person other than the person doing the original image interpretation shall

perform an initial quality control review of the image interpretation for the 

entire project area. Producers shall provide an opportunity for review by 

other interested agencies and stakeholders prior to submission to the FWS 

for inclusion in the NSDI. Names and affiliations of the reviewers of the 

data shall be included in the metadata.

 

2.1 Imagery

Source imagery is the imagery used to develop signatures and interpret 

wetlands. The source imagery used shall be color infrared at a minimum 
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of 1m resolution1or as specified in Table 1, in order to provide the 

required target mapping unit (TMU) and producer’s accuracy (PA) metrics 

(see section 2.3 Accuracy for more information on TMU and PA). Using 

a resolution of less than 1m (higher detail) will enhance the capability to 

meet the minimum requirements. The purpose of specifying source 

imagery requirements is to ensure meeting the TMU and PA metrics. 

Base imagery is the ortho-rectified imagery (aerial photography/satellite 

imagery) that is used as the base image (map) to overlay wetlands data. 

The base imagery shall be rectified to a national standard dataset. Digital 

Orthophoto Quarter Quads (DOQQs) at 1:12,000 scale are currently the 

most widely used base imagery. The purpose of specifying base imagery 

requirements is to produce a high detail and consistent wetland data layer. 

2.1.1 Source Imagery

Table 1. Spatial Resolution Requirements of Source Imagery 

Lower 48 States, 

Hawaii, & Territories

*

Estuarine & 

Lacustrine 

Deepwater **

Alaska (Including 

Deepwaters) 

R

esolution

1m 3m 5m

*Includes the lower 48 states, Hawaii, District of Columbia, Trust Territories, Puerto Rico, and the 

Virgin Islands. Estuarine and lacustrine deepwater habitats are excluded. Alaska is also excluded.

**Includes the Estuarine and Lacustrine deepwaters of the lower 48 states, Hawaii, District of 

Columbia, Trust Territories, Puerto Rico, and the Virgin Islands. Alaska is excluded.

Additional incorporation of any of the imagery source(s) from the 

following list will enhance data quality. 

Near-infrared wavelength imagery

Stereoscopic imagery

Leaf-off imagery 

Source imagery at a scale greater than 1:40,000 (higher detail) 

In some situations, incorporation of some of these imagery sources may be 

necessary to achieve the completeness and accuracy requirements 

specified in this Standard. To better interpret to the subclass level, multiseasonal imagery may be desirable.

 

1

For example, source imagery scales of 1:40,000 or greater (higher detail) should be sufficient to 

produce 1m resolution.
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2.1.2 Base Imagery

The minimum requirement for this Standard is that all base imagery shall

have a true spatial resolution and scale based on the geographic context of 

the mapping effort (Table 2).

Table 2. Spatial Resolution Requirements of Base Imagery

Lower 48 States, 

Hawaii,

& Territories *

Estuarine & Lacustrine 

Deepwater **

Alaska (Including 

Deepwaters)

R

esolution

1m 3m 5m

S

cale

1:12,000 1:24,000 1:63,360

*Includes the lower 48 states, Hawaii, District of Columbia, Trust Territories, Puerto Rico, and the 

Virgin Islands. Estuarine and lacustrine deepwater habitats are excluded. Alaska is also excluded.

**Includes the Estuarine and Lacustrine deepwaters of the lower 48 states, Hawaii, District of 

Columbia, Trust Territories, Puerto Rico, and the Virgin Islands. Alaska is excluded.

2.2 Classification

The FGDC Wetlands Mapping Standard is based upon the classification 

system described in the FGDC endorsed standard, Wetlands and 

Deepwater Habitats of the United States. The minimum standard for the 

completeness of the wetland classification is: ecological system, 

subsystem (with the exception of Palustrine), class, subclass (only 

required for forested, scrub-shrub, and emergent classes), water regime, 

and special modifiers (only required where applicable). The minimum 

standard for deepwater habitat classification is: system, subsystem, class, 

and water regime. Table 3 represents required classifications based on 

habitat type (see Appendix A for details). Further recommendations for 

classification are discussed in Appendix B. 
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Table 3. Classification Levels Required Based on Habitat Type

System Subsystem Class Subclass

 Water 

Regime

Special 

Modifiers 

(where 

applicable)

Lower 48 

States, 

Hawaii, &

Territories *

Yes Yes Yes Yes Yes Yes***

Estuarine & 

Lacustrine 

Deepwater **

Yes Yes Yes  Yes** *** Yes No

Alaska 

(Including 

Deepwaters)

Yes Yes Yes Yes Yes Yes***

At a minimum users shall include Subclass for forested, and scrub-shrub classes.

*Includes the lower 48 states, Hawaii, District of Columbia, Trust Territories, Puerto Rico, and the 

Virgin Islands. Estuarine and lacustrine deepwater habitats are excluded. Alaska is also excluded.

**Includes the Estuarine and Lacustrine deepwaters of the lower 48 states, Hawaii, District of 

Columbia, Trust Territories, Puerto Rico, and the Virgin Islands. Alaska is excluded.

***Farmed wetlands need only include system and farmed modifier; cultivated cranberry bogs may 

be classified as PSSf.

 Classify as unconsolidated bottom unless data indicates otherwise for estuarine and lacustrine 

deepwater habitats. 

** ***Users should include Class and Subclass when data are available for estuarine and lacustrine 

deepwater habitats; for other areas Class will suffice.

2.3 Accuracy 

Accuracy is a measure of both errors of omission and commission. For 

wetland mapping, accuracy may be dependent upon several factors 

affecting identification including:

 

Scale of imagery

Mapping scale or base map scale 

Quality of imagery

Season of imagery (leaf-off or leaf-on)

Type of imagery or emulsion of imagery

Environmental conditions when imagery was captured

Difficulty of identifying particular types of wetlands

Availability and quality of ancillary or collateral data sources

Accuracy is also a function of data quality and technology as well as 

proper training of the image interpreter. Classification accuracy of the 

final map product should be measured by the TMU and PA metrics. This 

Standard presents no requirement for User’s Accuracy (UA). 

The Target Mapping Unit is an estimate of the size class of the 

smallest wetland that can be consistently mapped and classified at a 
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particular scale of imagery, and that the image-interpreter attempts to 

map consistently. TMU allows for mapping below a specified 

threshold, but does not subject that finer detailed mapping to the 

accuracy requirements of the Standard. The size of a TMU is based on 

a simple square or a circle shape (a polygon with significant interior 

area relative to its perimeter) and not a long, narrow rectangle (i.e., a 

linear feature with little or no discernable interior area at the scale of 

interest). Therefore, wetlands which appear long and narrow (less 

than 15 feet wide at a scale of 1:12,0002), such as those following 

drainage-ways and stream corridors, are excluded from consideration 

when establishing the TMU. Such wetlands may or may not be 

mapped, depending on project objectives. 

Producer's Accuracy measures the percentage of wetland features 

that are correctly identified and correctly classified on the imagery. 

PA is measured by both feature and attribute accuracy. Feature 

accuracy is the correctness of the identification of wetland vs. nonwetland. Attribute accuracy is the correctness of the classification of 

the wetlands using the FGDC Wetlands Classification Standard. 

User’s Accuracy measures the percentage of reference sites on the 

ground (field-check) sites that are correctly classified on the map. This 

Standard presents no requirement for User’s Accuracy.

Spatial accuracy is a function of two metrics: Horizontal Accuracy and 

Vertical Accuracy.

Horizontal Accuracy refers a feature’s horizontal positional accuracy 

in relation to the base imagery.

Vertical Accuracy is a measure of the positional accuracy of a dataset 

with respect to a specified vertical datum.

Requirements for these accuracy metrics are presented in the following 

sub-sections. This Standard presents no requirement for Vertical 

Accuracy.

2.3.1 Target Mapping Unit and Producer’s Accuracy

 

2 The 15 feet wide measurement for linear features is specified because when viewed at a scale of 

1:12,000, two lines bounding a polygon will converge if the polygon is less than 15 feet wide.
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Wetlands data that meet or exceed the minimum TMU and PA

requirements will be accepted for submission to the NSDI. Ninety-eight 

percent of all wetlands visible on an image, at the size of the TMU or 

larger shall be mapped regardless of the origin (natural, farmed, or 

artificial). For the lower 48 states and Hawaii and the Trust Territories, 

features that are at least 0.5 acres shall be mapped with a demonstrated PA 

of 98% for feature accuracy and 85% for attribute accuracy, or higher,

across each DOQQ (or the project area if the project area is smaller than a 

DOQQ), as documented through external quality assessment of samples.

The minimum technical requirements are specified in Table 4. Habitat 

changes that have occurred between the date of the base imagery and the 

date of field observation/groundtruthing are not considered errors because 

the wetland was correctly classified on the base imagery. 

Table 4. TMU and PA Requirements

Lower 48 States, 

Hawaii, 

& Territories *

Estuarine & 

Lacustrine 

Deepwater **

Alaska (Including 

Deepwaters) 

TMU 0.5 acres (0.2 ha) 1.0 acres (0.4 ha) 5.0 acres (2.0 ha)

Feature Accuracy 

(Wetland 

Identification)

98% 98% 98%

Attribute 

Accuracy (FGDC 

Wetlands 

Classification)

85% 85% 85%



PA across each DOQQ (or the project area if the project area is smaller than a DOQQ), as 

documented through external quality assessment of samples.

*Includes the lower 48 states, Hawaii, District of Columbia, Trust Territories, Puerto Rico, and the 

Virgin Islands. Estuarine and lacustrine deepwater habitats are excluded. Alaska is also excluded.

**Includes the Estuarine and Lacustrine deepwaters of the lower 48 states, Hawaii, District of 

Columbia, Trust Territories, Puerto Rico, and the Virgin Islands. Alaska is excluded.

The actual TMU and PA for the project area shall be declared in the 

metadata, along with an associated justification and description of the 

quality assurance process used. 

2.3.2 Horizontal Accuracy

Horizontal accuracy is ensured by conformance with FGDC DOQQ 

requirements used by many Federal agencies3. The FGDC Wetlands 

 

3

FGDC Content Standards for Digital Orthoimagery

http://www.fgdc.gov/standards/projects/FGDC-standards-projects/orthoimagery/orth_299.pdf

USGS Digital Orthophoto Standards
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Mapping Standard requires that spatial accuracies are reported at the 90% 

or 95% confidence interval. Conformance with FGDC DOQQ 

requirements ensures the horizontal accuracy will meet the 95% 

confidence level. Accuracy reported at the 95% confidence level means 

that 95% of the positions in the data set will have an error with respect to 

true ground position that is equal to or smaller than the reported accuracy 

value. The reported accuracy value reflects all uncertainties, including 

those introduced by geodetic control coordinates, compilation, and final 

computation of ground coordinate values in the product. 

The horizontal accuracy minimum requirement is commensurate with the 

base imagery/map scale available for the area (see Table 2). Please 

consult Section 3.2.3, Accuracy reporting, of Geospatial Positioning 

Accuracy Standards, Part 3: National Standard for Spatial Data Accuracy, 

for reporting multiple accuracies in a data set. This Standard requires a 

nominal RMSE commensurate with the context of the mapping as 

specified in Table 5. 

Table 5. Horizontal RMSE Accuracy Requirements

Lower 48 States, 

Hawaii, 

& Territories *

Estuarine & 

Lacustrine 

Deepwater **

Alaska (Including 

Deepwaters) 

Horizontal RMSE 

Accuracy 5m 15m 25m

*Includes the lower 48 states, Hawaii, District of Columbia, Trust Territories, Puerto Rico, and the 

Virgin Islands. Estuarine and lacustrine deepwater habitats are excluded. Alaska is also excluded.

**Includes the Estuarine and Lacustrine deepwaters of the lower 48 states, Hawaii, District of 

Columbia, Trust Territories, Puerto Rico, and the Virgin Islands. Alaska is excluded. 

2.4 Data Verification

The overall guiding principle is that the digital wetlands data added are 

added to the wetlands spatial data layer of the NSDI. To ensure quality 

control, the verification checks described below shall be followed prior to 

submission for inclusion in the NSDI. As the appointed steward for the 

national wetlands data layer, the FWS will determine if wetlands data 

submitted for inclusion in the NSDI is the best available data and, if so, 

will conduct the necessary data verification, quality control, and quality 

assurance procedures described in Section 2 of this document.

2.4.1 Logical Consistency

 

http://rockyweb.cr.usgs.gov/nmpstds/doqstds.html
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14

Logical consistency refers to the internal consistency of the data structure, 

and particularly applies to topological consistency. This Standard’s intent 

is to ensure the ability to generate seamless digital mapping products 

within a project area. Tests for logical consistency shall be performed that 

verify topology validity prior to submission to the NSDI. 

The minimum requirement for topological verification includes:

Polygons intersecting the border of a project area shall be closed 

along the border. 

Segments making up the outer and inner boundaries of a polygon tie 

end-to-end to completely enclose the area. 

Line segments shall be a set of sequentially numbered coordinate 

pairs. 

Neither duplicate features nor duplicate points exist in a data string. 

Intersecting lines are separated into individual line segments at the 

point of intersection. 

All nodes are represented by a single coordinate pair which indicates

the beginning or end of a line segment. 

2.4.2 Edge Matching

Edge-matching of wetland interpretation is required for a seamless 

wetlands database. There are two types of edge-matching: 1) internal ties 

along the borders of source images, and 2) external ties to pre-existing 

wetland data immediately adjacent to the project area. 

The Standard requires that in all cases, internal edge-matching will be 

performed. Wetland mapping units lying along the outer borders of source 

images within a project area, whenever practical will be edge-matched 

with interpretations on all adjacent images within the project area. All 

linear and polygon features will be edited to ensure an identical or 

coincident transition across images in the entire project area. At a 

minimum, features located on the outer edge of the project area will be 

closed exactly at the border of the project area.

2.4.3 Attribute Validity

This Standard requires that all polygons have a valid attribute code to 

depict wetland habitat type. To avoid attribute errors, all data submissions 

shall be run through attribute verification checks prior to submission to 

FWS by the map producer, and then again by FWS before inclusion in the 
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15

NSDI. 

The FWS Attribution Tools have been constructed to attribute map 

features that may depict wetlands, riparian areas, uplands or other natural 

resource features. These tools can also serve as a reference for uncommon 

or rarely used codes or to assist users who are not familiar with the 

alphanumeric wetland mapping codes. The main Attribution Tool contains 

the entire hierarchical scheme for classifying wetlands and deepwater 

habitats (Cowardin et al, 1979). These tools are available at:

http://www.fws.gov/wetlands/Data/Tools.html.

2.5 Datum and Projection

Wetlands data may be created or used in any standard datum and 

projection. However, in accordance with the FWS standard operating 

procedures, the FGDC Wetlands Mapping Standard requires all data to be 

re-projected to Albers Equal-Area projection and the datum to be North 

American Datum 1983 (NAD83), or more recent, prior to submission for 

inclusion in NSDI. 

2.6 Metadata

Metadata shall be provided by the map producer and conform to the most 

recent FGDC Content Standard for Digital Geospatial Metadata 

(CSDGM). Adherence to the Standard requires all metadata to include a 

description of the data verification, quality control, and quality assurance 

steps performed on the wetlands data to meet core accuracy requirements. 

FWS will validate the presence of required metadata prior to submission 

for inclusion in NSDI.

All metadata for derived wetland classifications shall contain a reference 

to the FGDC-STD-004 Wetlands and Deepwater Habitat Classification 

System.

2.7 FWS Coordination and Quality Control

Mapping organizations are advised to consult with FWS to coordinate any 

federally-funded wetlands mapping effort. Requirements for QC 

procedures are listed under the Source section of the table available at:

http://www.fws.gov/stand/standards/dl_wetlands_WWW.html.

The mapping organization should coordinate mapping activities with FWS 

to assure a logical, technically sound, and comprehensive approach. 

Mapping organizations shall run data through the FWS Attribution Tools 
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Wetlands Mapping Standard

16

(see 2.4) before providing the final finished project data to the FWS. FWS 

will be responsible for final quality control of all products.
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17

REFERENCES

Classification of Wetlands and Deepwater Habitats in the United States, 

FGDC-STD-004 (also referred to as Cowardin Classification System in 

the Standard)

http://www.fws.gov/wetlands/_documents/gNSDI/ClassificationWetlands

DeepwaterHabitatsUS.pdf

Content Standard for Digital Geospatial Metadata (version 2.0) FGDCSTD-001-1998, http://www.fgdc.gov/metadata/geospatial-metadatastandards

National Hydrography Database (NHD) maintained by the USGS at 

http://nhd.usgs.gov/

Draft FGDC Riparian Standard maintained by FGDC at

http://www.fgdc.gov/standards/projects/FGDC-standardsprojects/riparian-mapping/index_html

Fish and Wildlife Service National Standards and Quality Components for 

Wetlands, Deepwater and Related Habitat Mapping, 

http://www.fws.gov/stand/standards/dl_wetlands_National%20Standards.

doc

Geospatial Positioning Accuracy Standards Part 3. National standard for 

spatial data accuracy. FGDC-STD-007.3-1998

Guidance for Benthic Habitat Mapping: An Aerial Photographic 

Approach maintained by the U.S. NOAA Coastal Services Center. 

Available for download at

http://www.csc.noaa.gov/benthic/mapping/pdf/bhmguide.pdf

National Vegetation Classification Standard, FGDC-STD-005

http://www.fgdc.gov/standards/projects/FGDC-standardsprojects/vegetation/NVCS_V2_FINAL_2008-02.pdf/

RAMSAR Classification for Wetland Type maintained by Convention on 

Wetlands (Ramsar, Iran, 1971) at 

http://www.ramsar.org/ris/key_ris_types.htm

U.S. Geological Survey. 2001. Standards for revised primary service 

quadrangle maps. Part 2 specifications. National Mapping Technical 

Instructions. U.S. Department of the Interior, U.S. Geological Survey, 

Reston, VA. 76p. plus appendices.
Federal Geographic Data Committee FGDC Document Number FGDC-STD-015-2009

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Primary Indicators Method. Tiner, R.W. 1993. The primary indicators 

method - a practical approach to wetland recognition and delineation in 

the United States. Wetlands 13(1): 50-64,

http://www.fws.gov/wetlands/_documents/gOther/PrimaryIndicatorsMethod.pdf
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Appendix A: Attributes for Wetland Classification (Normative)

19

APPENDIX A: 

ATTRIBUTES FOR WETLAND CLASSIFICATION

(NORMATIVE)
Federal Geographic Data Committee FGDC Document number FGDC-STD-015-2009

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Appendix A: Attributes for Wetland Classification (Normative)

20

The following keys in Figures 1a and 1b provide a list of codes for writing alpha-numeric designations for wetlands and deepwater 

habitats as defined by the wetlands classification system developed by the U.S. Fish and Wildlife Service (Cowardin et al. 1979). 

Three examples of the use of the codes follow: E2EM1P = estuarine (E) intertidal (2) emergent wetland (EM) persistent (1) irregularly 

flooded (P); PFO1Ad = palustrine (P) forested wetland (FO) broad-leaved deciduous (1) temporarily flooded (A) partly 

drained/ditched (d); L2AB3Fh = lacustrine (L) littoral (2) aquatic bed (AB) rooted vascular (3) semipermanently flooded (F) 

diked/impounded (h).
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Appendix A: Attributes for Wetland Classification (Normative)

21

Figure 1a: Wetlands and Deepwater Habitats

EM – Emergent 2 Nonpersistent

1 - Subtidal M - Marine 2 - Intertidal RB – Rock Bottom 1 Bedrock 2 Rubble UB – Unconsolidated Bottom 1 Cobble-Gravel 2 Sand 3 Mud AB – Aquatic Bed 1 Algal 3 Rooted Vascular

RF – Reef 1 Coral 3 Worm RF – Reef 1 Coral 3 Worm AB – Aquatic Bed 1 Algal 3 Rooted Vascular US – Unconsolidated Shore 1 Cobble-Gravel 2 Sand 3 Mud 4 Organic RS – Rocky Shore 1 Bedrock 2 Rubble

System

Subsystem

Class

Subclass

WETLANDS AND DEEPWATER HABITATS CLASSIFICATION

1 - Subtidal E - Estuarine 2 - Intertidal RB – Rock Bottom 1 Bedrock 2 Rubble

UB – Unconsolidated Bottom 1 Cobble-Gravel 2 Sand 3 Mud 4 OrganicAB – Aquatic Bed 1 Algal 3 Rooted Vascular 4 Floating VascularRF – Reef 2 Mollusk 3 Worm RF – Reef 2 Mollusk 3 Worm AB – Aquatic Bed 1 Algal 3 Rooted Vascular 4 Floating Vascular US – Unconsolidated Shore 1 Cobble-Gravel 2 Sand 3 Mud 4 Organic RS – Rocky Shore 1 Bedrock 2 Rubble

System

Subsystem

Class

Subclass SB – Streambed 1 Bedrock 2 Rubble 3 Cobble-Gravel 4 Sand 5 Mud 6 Organic EM – Emergent 1 Persistent 2 Non- persistent 5 Phragmites australis

SS – Scrub- Shrub 1 Broad-Leaved Deciduous 2 Needle-Leaved Deciduous 3 Broad-Leaved Evergreen 4 Needle-Leaved Evergreen 5 Dead 6 Deciduous 7 EvergreenFO – Forested 1 Broad-Leaved Deciduous 2 Needle-Leaved Deciduous 3 Broad-Leaved Evergreen 4 Needle-Leaved Evergreen 5 Dead 6 Deciduous System R - Riverine 7 Evergreen Subsystem Class

Subclass

Classification of Wetlands and Deepwater Habitats of the United States, Cowardin et al. 1979

RB – Rock Bottom 1 Bedrock 2 RubbleUB – Unconsolidated Bottom 1 Cobble-Gravel 2 Sand 3 Mud 4 Organic AB – Aquatic Bed 1 Algal 2 Aquatic Moss 3 Rooted Vascular 4 Floating Vascular US – Unconsolidated Shore 1 Cobble-Gravel 2 Sand 3 Mud 4 Organic 5 Vegetated RS – Rocky Shore 1 Bedrock 2 Rubble SB*** – Streambed 1 Bedrock 2 Rubble 3 Cobble-Gravel 4 Sand 5 Mud 6 Organic 7 Vegetated

1 - Tidal 2 – Lower Perennial 3 – Upper Perennial 4* - Intermittent 5** – Unknown Perennial

* Intermittent is limited to the Streambed Class ** Unknown Perennial is limited to Unconsolidated Bottom *** Streambed is limited to Tidal and Intermittent Subsystems Page 1 of 2
Federal Geographic Data Committee FGDC Document number FGDC-STD-015-2009

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Appendix A: Attributes for Wetland Classification (Normative)

22

Figure 1b: Wetlands and Deepwater Habitats Classification
Federal Geographic Data Committee FGDC Document number FGDC-STD-015-2009

Wetlands Mapping Standard

Appendix B: Attributes for LLWW (for Landscape, Landform, Water Flow path, and Waterbody Type) 

(Informative)

23

APPENDIX B:

ATTRIBUTES FOR LLWW (FOR LANDSCAPE, LANDFORM, WATER FLOW 

PATH, AND WATERBODY TYPE)

(INFORMATIVE)
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Appendix B: Attributes for LLWW (for Landscape, Landform, Water Flow path, and Waterbody Type) 

(Informative)

24

The following keys provide a list of other descriptors that have been developed by the 

U.S. Fish and Wildlife Service to describe other wetland properties not currently 

addressed in Cowardin et al. 1979 wetland classification system. When added to existing 

NWI wetland classifications, the expanded wetland database becomes a more powerful 

analytical tool, allowing users to predict wetland functions for large geographic areas,

better characterize wetlands (e.g., palustrine wetlands associated with lakes, rivers, 

streams, and ponds), and generate information of interest to policymakers and others 

(e.g., how many and how much of the wetland resource is isolated or connected to waters 

of the United States). When the Cowardin et al. classification is reviewed in the future, it 

is likely that these attributes in whole or part will be added to the classification. This 

operational draft system is referred to informally as LLWW (for Landscape, Landform, 

Water Flow path, and Waterbody type).

Simplified Keys for Classifying Tidal and Nontidal Wetlands by

Landscape Position, Landform, and Water Flow Path (Adapted from Tiner 2003)

Landscape Position

1. Wetland borders a river, stream, lake, reservoir, in-stream pond, estuary, or ocean ......2

1. Wetland does not border one of these waterbodies; it is surrounded by upland or

borders a pond that is surrounded by upland ............................................................Terrene

2. Wetland lies along an ocean shore and is subject to tidal flooding.......................Marine

2. Wetland does not lie along an ocean shore or if oceanside, it is not subject to tidal 

flooding................................................................................................................................3

3. Wetland lies along an estuary (salt-brackish waters) and is subject to tidal 

flooding.................................................................................................................. Estuarine

3. Wetland does not lie along an estuary or if along the estuary, it is not subject to tidal 

flooding................................................................................................................................4

4. Wetland lies along a lake or reservoir or within its basin (i.e., the relatively flat plain 

contiguous to the lake or reservoir) ............................................................................ Lentic

4. Wetland lies along a river or stream, or in-stream pond, or borders a marine or 

estuarine wetland or associated waters but is not flooded by tides (except 

episodically).........................................................................................................................5

5. Wetland is associated with a river or stream...................................................................6

5. Wetland is not associated with a river or stream; it is a freshwater nontidal wetland

bordering a marine or estuarine wetland or associated waters .................................Terrene

6. Wetland is the source of a river or stream and this watercourse does not flow through

the wetland................................................................................................................Terrene

6. A river or stream flows through or alongside the wetland .............................................7

7. Wetland is periodically flooded by river or stream ................................................Lotic4

7. Wetland is not periodically flooded by the river or stream .................................Terrene

 

4 Lotic wetlands are separated into river and stream sections (based on watercourse width: polygon = Lotic River vs. 

linear = Lotic Stream at a scale of 1:24,000) and then divided into one of five gradients: 1) high (e.g., shallow mountain 

streams on steep slopes), 2) middle (e.g., streams with moderate slopes), 3) low (e.g., mainstem rivers with 

considerable floodplain development and slow-moving streams), 4) intermittent (periodic flows), and 5) tidal 

(hydrology under the influence of the tides).
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Appendix B: Attributes for LLWW (for Landscape, Landform, Water Flow path, and Waterbody Type) 

(Informative)

25

Landform

1. Wetland occurs on a slope >2% .............................................................................. Slope

1. Wetland does not occur on a slope>2% ..........................................................................2

2. Wetland forms an island completely surrounded by water .....................................Island

2. Wetland does not form an island.....................................................................................3

3. Wetland occurs in the shallow water zone of a permanent nontidal waterbody, the 

intertidal zone of an estuary with unrestricted tidal flow, or the regularly flooded 

(daily tidal inundation) zone of freshwater tidal wetlands..................................... Fringe

3. Wetland does not occur in these waters or in estuarine intertidal zones with 

unrestricted tidal flow......................................................................................................4

4. Wetland occurs in a portion of an estuary with restricted tidal flow due to tide 

gates, undersized culverts, dikes of similar obstructions ........................................ Basin 

4. Wetland does not occur in such location.........................................................................5

5. Wetland forms a nonvegetated bank or is within the banks of a river or stream ... Fringe

5. Wetland is a vegetated river or stream bank or not within the banks..............................6

6. Wetland occurs on an active alluvial plain of a river (a polygonal feature)5... Floodplain*

6. Wetland does not occur on an active floodplain..............................................................7

7. Wetland occurs on a broad interstream divide (including headwater positions) 

associated with coastal or glaciolacustrine plains or similar plains..................Interfluve*

7. Wetland does not occur on such a landform....................................................................8

8. Wetland occurs in a distinct depression................................................................... Basin

8. Wetland occurs on a nearly level landform ................................................................ Flat

----------------------

*Basin and Flat sub-landforms can be identified within these landforms when desirable.

 

5

For practical purposes, floodplain is restricted to rivers (i.e., polygonal watercourses); similar areas along streams 

(i.e., linear watercourses) are designated as basins or flats.
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Appendix B: Attributes for LLWW (for Landscape, Landform, Water Flow path, and Waterbody Type) 

(Informative)

26

Water Flow Path6

1. Wetland is typically surrounded by upland (nonhydric soil); receives precipitation

and runoff from adjacent areas with no apparent outflow7.................................. Isolated**

1. Wetland is not geographically isolated ...........................................................................2

2. Water flow is mainly bidirectional from tides or lake/reservoir fluctuations .................3

2. Water flow is essential one-directional (downstream)....................................................4

3. Wetland is subjected to tidal flooding................................................Bidirectional-Tidal

3. Wetland is located along a lake or reservoir and not along a river or stream entering 

this type of waterbody; water levels are mainly affected by the rise and fall of lake 

reservoir water levels.....................................................................Bidirectional-Nontidal***

4. Wetland is a sink, receiving water from a river, stream, or other surface water source 

and lacking surface-water outflow .........................................................................Inflow

4. Wetland is not a sink; surface water flows through or out of the wetland ......................5

5. Water flows out of the wetland, but does not flow into this wetland from another 

source................................................................................................................... Outflow

5. Water flows through the wetland, often coming from upstream or uphill sources 

(typically wetlands along rivers and streams) ............................................. Throughflow

-----------------------

**Wetland is geographically isolated; hydrological relationship to other wetlands and watercourses may 

be more complex than can be determined by simple visual assessment of surface water conditions. If 

groundwater relationships are known can apply other water flow paths as appropriate, but add 

“groundwater” to the term (e.g., outflow-groundwater).

***Bidirectional-Nontidal flow could be expanded to reference the water flow path of the associated 

waterbody: Bidirectional-nontidal/throughflow, Bidirectional-nontidal/inflow, Bidirectionalnontidal/outflow, and Bidirectional-nontidal/isolated.

Waterbody Types from Dichotomous Key

 

6

Surface water connections are emphasized because they are more readily identified than groundwater linkages (see 

footnote below for paludified landscapes).

7 Water flow path for some bogs and similar wetlands may be paludified; paludification processes occur in areas of low 

evapotranspiration and high rainfall, peat moss moves uphill creating wetlands on hillslopes (i.e., wetland develops 

upslope of primary water source).
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Appendix B: Attributes for LLWW (for Landscape, Landform, Water Flow path, and Waterbody Type) 

(Informative)

27

List of Estuary, Ocean, River, Stream, Lake, and Pond Types 

(with corresponding map codes assigned)

EY Estuary

1 drowned river valley estuary

 a open bay (fully exposed)

 b semi-enclosed bay

 c river channel

2 bar-built estuary

 a coastal pond-open

 b coastal pond-seasonally closed

 c coastal pond-intermittently open

 d hypersaline lagoon

3 river-dominated estuary

4 rocky headland bay estuary

 a island protected

5 island protected estuary

6 shoreline bay estuary

 a open (fully exposed)

 b semi-enclosed

7 tectonic

 a fault-formed

 b volcanic-formed

8 fjord

9 other

Note: If desired, you can also designate river channel (rc), stream channel (sc),and 

inlet channel (ic) by modifiers. Examples: EY1rc = Drowned River Valley 

Estuary river channel; EY2ic= Bar-built estuary inlet channel. If not, simply 

classify all estuarine water as a single type, e.g., EY1 for Drowned River Valley 

or EY2 for Bar-built Estuary.

OB Ocean or Bay

1 open (fully exposed)

2 semi-protected oceanic bay

3 atoll lagoon

4 other reef-protected waters

5 fjord

RV River
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(Informative)

28

1 low gradient

 a connecting channel

 b canal

2 middle gradient

 a connecting channel

3 high gradient

 a waterfall

 b riffle

 c pool

4 intermittent gradient

5 tidal gradient

6 dammed gradient

 a lock and dammed

 b run-of-river dammed

 c other dammed

ST Stream

1 low gradient

 a connecting channel

2 middle gradient

 a connecting channel

3 high gradient

 a waterfall

 b riffle

 c pool

4 intermittent gradient

5 tidal gradient

6 dammed

 a lock and dammed

 b run-of-river dammed

 c beaver dammed

 d other dammed

7 artificial

 a connecting channel

 b ditch

LK Lake

1 natural lake (see also Pond codes for possible specific types)

 a main body

 b open embayment

 c semi-enclosed embayment

 d barrier beach lagoon

2 dammed river valley lake
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Appendix B: Attributes for LLWW (for Landscape, Landform, Water Flow path, and Waterbody Type) 

(Informative)

29

 a reservoir

 b hydropower

 c other

3 other dammed lake

 a former natural 

 b artificial

4 other artificial lake

PD Pond

1 natural

 a bog

 b woodland-wetland

 c woodland-dryland

 d prairie-wetland (pothole)

 e prairie-dryland (pothole)

 f playa

 g polygonal

 h sinkhole-woodland

 i sinkhole-prairie

 j Carolina bay

 k pocosin

 l cypress dome

 m vernal-woodland

 n vernal-West Coast

 o interdunal

 p grady

 q floodplain

 r other

2 dammed/impounded

 a agriculture

 a1 cropland

 a2 livestock

 a3 cranberry

 b aquaculture

 b1 catfish

 b2 crayfish

 c commercial

 c1 commercial-stormwater

 d industrial

 d1 industrial-stormwater

 d2 industrial-wastewater

 e residential

 e1 residential-stormwater

 f sewage treatment
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(Informative)

30

 g golf

 h wildlife management

 i other recreational

 o other

3 excavated

 a agriculture

 a1 cropland

 a2 livestock

 a3 cranberry

 b aquaculture

 b1 catfish

 b2 crayfish

 c commercial

 c1 commercial-stormwater

 d industrial

 d1 industrial-stormwater

 d2 industrial-wastewater

 e residential

 e1 residential-stormwater

 f sewage treatment

 g golf

 h wildlife management

 i other recreational

 j mining

 j1 sand/gravel

 j2 coal

 o other

4 beaver

5 other artificial

Source: Tiner, R.W. 2003. Dichotomous Keys and Mapping Codes for Wetland 

Landscape Position, Landform, Water Flow Path, and Waterbody Type Descriptors. U.S. 

Fish and Wildlife Service, National Wetlands Inventory Program, Northeast Region, 

Hadley, MA. 44 pp.

http://library.fws.gov/wetlands/dichotomouskeys0903.pdf
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Appendix C: Definitions (Informative)

31

APPENDIX C:

DEFINITIONS

(INFORMATIVE)
Federal Geographic Data Committee FGDC Document number FGDC-STD-015-2009 

Wetlands Mapping Standard

Appendix C: Definitions (Informative)

32

Commission error – commission errors are errors related to 

misclassification or limits of scale. For wetland mapping, commission 

errors include: 1) misclassification (e.g., nonwetland areas mapped as 

wetlands or misidentification of the wetland type), 2) small uplands 

included within a large wetland mapping unit, and 3) small wetlands of 

different type included within a larger wetland unit of another type (e.g., 

a small scrub-shrub wetland within a palustrine forested wetland 

mapping unit) simply because they are too small to map (below the target 

mapping unit). The latter two situations are commonly referred to as 

“inclusions.” Habitat changes that have occurred between the date of the 

base imagery and date of field observation/groundtruthing are not 

considered errors as the wetland was correctly classified on the base 

imagery. 

Cowardin classification system – the U.S. Fish and Wildlife Service’s 

official wetlands and deepwater habitat classification system written by 

Cowardin, Carter, Golet, and LaRoe and published in 1979, endorsed by 

the FGDC as Classification of Wetlands and Deepwater Habitats of the 

United States, FGDC-STD-004 in 1996.

estuarine and lacustrine deepwater – subtidal waters below the extreme 

spring low tide mark in estuaries and tidal freshwater lakes and nontidal 

waters of lakes deeper than 2 m at annual low water; "deepwater" 

excludes the shallow water zone of lakes (lacustrine littoral wetlands).

federally-funded – financial support for the mapping project comes 

directly or indirectly from one or more federal agencies.

final map product – the final map product directed by this Standard is the 

incorporation of the interpreted and mapped wetlands within a project 

area into the Fish and Wildlife Service Wetland Database. Additional 

final map products may be required by the funding federal agencies.

horizontal accuracy – refers to a feature’s spatial relationship to the base

imagery.

imagery – in the context of wetland mapping, imagery is a picture or 

digital representation of an area captured through remote sensing 

instruments (e.g., aerial cameras or other sensors) that yield information 

about the Earth; imagery includes aerial photographs and digital 

geospatial imagery for computer analyses, but does not include maps 

(cartographic products - e.g., topographic maps and planimetric maps).

logical consistency – logical consistency refers to the internal 

consistency of the data structure, and particularly applies to topological 

consistency. 

non-federally funded – financial support comes from state, local, or 

private funds with no contribution either directly or indirectly from 

Federal sources.
Federal Geographic Data Committee FGDC Document number FGDC-STD-015-2009 

Wetlands Mapping Standard

Appendix C: Definitions (Informative)

33

National Spatial Data Infrastructure (NSDI) – consistent means to share 

geographic data among all users could produce significant savings for 

data collection and use and enhance decision making. Executive Order 

12906 calls for the establishment of the National Spatial Data 

Infrastructure defined as the technologies, policies, and people necessary 

to promote sharing of geospatial data throughout all levels of 

government, the private and non-profit sectors, and the academic 

community. 

The goal of this Infrastructure is to reduce duplication of effort 

among agencies, improve quality and reduce costs related to 

geographic information, to make geographic data more accessible to 

the public, to increase the benefits of using available data, and to 

establish key partnerships with states, counties, cities, tribal nations, 

academia and the private sector to increase data availability. 

The NSDI has come to be seen as the technology, policies, criteria, 

standards and people necessary to promote geospatial data sharing 

throughout all levels of government, the private and non-profit 

sectors, and academia. It provides a base or structure of practices 

and relationships among data producers and users that facilitates 

data sharing and use. It is a set of actions and new ways of 

accessing, sharing and using geographic data that enables far more 

comprehensive analysis of data to help decision-makers choose the 

best course(s) of action. Much has been accomplished in recent 

years to further the implementation of the NSDI, but there is still 

much to be done to achieve the vision of current and accurate 

geographic data being readily available across the country.

omission errors – for wetland mapping, omission errors are wetlands that 

are not identified on the map. Wetlands may be omitted due to several 

factors that preclude their identification or delineation including scale 

and emulsion of imagery, mapping scale or base map scale, quality of 

imagery, environmental conditions when imagery was captured, and 

difficulty of identifying particular types of wetlands. 

Producer’s Accuracy (PA) – measures the percentage of features that are 

correctly classified on the imagery. PA is measured by both feature and 

attribute accuracy. Feature accuracy is the correctness of the 

identification of wetland vs. non-wetland. Attribute accuracy is the 

correctness of the classification of the wetlands using the FGDC 

Wetlands Classification Standard.

project area – a geographic area where wetland mapping is to be 

performed through some form of remote sensing (e.g., 

photointerpretation, satellite or other image processing). It may range in 

size from a region, state, county, or municipality or to portion thereof. 

For purposes of this Standard, a project area is not a site-specific area 
Federal Geographic Data Committee FGDC Document number FGDC-STD-015-2009 

Wetlands Mapping Standard

Appendix C: Definitions (Informative)

34

where construction, restoration, or similar actions are proposed or where 

on-the-ground wetland delineations are performed. It would be best for 

project areas to be indexed and organized by USGS topographic 

quadrangles or DOQQs. The Fish and Wildlife Wetland Database 

recognizes only data input based on the USGS 7.5 minute quadrangle 

and DOQQ grid. 

spatial resolution – the detail with which a map depicts the location and 

shape of geographic features. The larger the map scale, the higher the 

possible resolution. As scale decreases, resolution diminishes and feature 

boundaries shall be smoothed, simplified, or not shown at all; for 

example, small areas may have to be represented as points.

Target Mapping Unit (TMU) – is an estimate of the size class of the 

smallest wetland that can be consistently mapped and classified at a 

particular scale of imagery, and that the image-interpreter attempts to 

map consistently. TMU allows for mapping below a specified threshold, 

but does not subject that finer detailed mapping to the accuracy 

requirements of the Standard. 

upland – “Upland” or “U” is the default classification for regions of the 

map that are not classified as wetlands or other aquatic habitats. As 

such, the designation “Upland” represents generalized terrestrial areas 

which have not been further subdivided or categorized by type. While 

“Upland” primarily includes terrestrial (non-wetland) areas and former 

wetlands that are effectively drained or filled, it may include unclassified 

wetlands such as human-modified areas (e.g., farmed wetlands), 

wetlands that are too small to be differentiated, wetlands that couldn’t be 

detected on the type of imagery used (e.g., small wetlands under forest 

cover), and other unintentional wetland omissions (errors). According to 

the FWS Wetlands Classification System (Cowardin et al, 1979):

The upland limit of wetland is designated as (1) the boundary 

between land with predominantly hydrophytic cover and land with 

predominantly mesophytic or xerophytic cover; (2) the boundary 

between soil that is predominantly hydric and soil that is 

predominantly nonhydric; or (3) in the case of wetlands without 

vegetation or soil, the boundary between land that is flooded or 

saturated at some time during the growing season each year and 

land that is not.

User’s Accuracy (UA) – measures the percentage of reference sites on 

the ground that are correctly classified on the map.

vertical accuracy – the measure of the accuracy of the vertical measure 

of a reference point. 

wetland classification – in support of maintaining an ecological 

perspective, wetlands are defined as below, based upon the FWS 
Federal Geographic Data Committee FGDC Document number FGDC-STD-015-2009 

Wetlands Mapping Standard

Appendix C: Definitions (Informative)

35

Wetlands Classification System (Cowardin et al, 1979). This definition 

is the national standard for wetland mapping, monitoring, and data 

reporting as recognized by the FGDC on December 17, 1996.

Wetlands are lands transitional between terrestrial and aquatic 

systems where the water table is usually at or near the surface or the 

land is covered by shallow water. 

For purposes of this classification wetlands must have one or more 

of the following three attributes: (1) at least periodically, the land 

supports predominantly hydrophytes, (2) the substrate is 

predominantly undrained hydric soil, and (3) the substrate is nonsoil 

and is saturated with water or covered by shallow water at some 

time during the growing season of each year.

wetlands inventory mapping – more detailed mapping and classification 

of wetlands beyond distinguishing wetland from non-wetland or between 

simple categories of forested and non-forested or vegetated and nonvegetated.