FGDC-STD-014.4-2008

Geographic Information Framework Data Content 

Standard 

Part 4: Geodetic Control 

May 2008 
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-STD-014.4-2008 

Geographic Information Framework Data Content Standard 

Part 4: Geodetic Control

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Contents 

Introduction................................................................................................................................... vi

1 Scope, purpose, and application .............................................................................................. 1

1.1 Scope................................................................................................................................. 1

1.2 Purpose ............................................................................................................................. 1

1.3 Application ........................................................................................................................ 1

2 Normative references................................................................................................................. 1

3 Maintenance authority ............................................................................................................... 1

3.1 Level of responsibility...................................................................................................... 1

3.2 Contact information ......................................................................................................... 2

4 Terms and definitions ................................................................................................................ 2

5 Symbols, abbreviated terms, and notations............................................................................ 4

6 Requirements.............................................................................................................................. 4

6.1 General .............................................................................................................................. 4

6.2 Designations ..................................................................................................................... 4

6.2.1 Unique identifier ............................................................................................................... 4

6.2.2 Descriptive identifier........................................................................................................ 5

6.2.3 URI...................................................................................................................................... 5

6.3 Coordinates....................................................................................................................... 5

6.3.1 General .............................................................................................................................. 5

6.3.2 Horizontal coordinates..................................................................................................... 5

6.3.3 Vertical coordinates ......................................................................................................... 5

6.4 Accuracy............................................................................................................................ 6

6.5 Geodetic datum ................................................................................................................ 6

6.5.1 General .............................................................................................................................. 6

6.5.2 Datum tag .......................................................................................................................... 6

6.5.3 Epoch date ........................................................................................................................ 6

7 Geodetic control Unified Modeling Language (UML) model.................................................. 7

7.1 Unified Modeling Language (UML) class diagram ........................................................ 7

7.2 UML objects ...................................................................................................................... 8

7.2.1 ControlPoint...................................................................................................................... 8

7.2.2 VerticalInformation........................................................................................................... 9

7.2.3 RS_Identifier.................................................................................................................... 10

7.3 HeightType code list ...................................................................................................... 11

Annex A (normative) Normative references ............................................................................. 12

Annex B (informative) Example of geodetic control data content ......................................... 13

Annex C (informative) User guidance for estimating local and network accuracy values.. 14

Annex D (informative) Control points and coordinated points .............................................. 15

Annex E (informative) Bibliography .......................................................................................... 16

Figures 

Figure 1 – Relationship between orthometric, ellipsoidal, and geoid heights........................ 6

Figure 2 – Geodetic control UML model ..................................................................................... 7
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Part 4: Geodetic Control

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Tables 

Table 1 – Data dictionary for ControlPoint ................................................................................. 8

Table 2 – Data dictionary for VerticalInformation ...................................................................... 9

Table 3 – Data dictionary for RS_Identifier............................................................................... 10

Table 4 – CodeList for HeightType ............................................................................................ 11
Federal Geographic Data Committee FGDC-STD-014.4-2008 

Geographic Information Framework Data Content Standard 

Part 4: Geodetic Control

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Foreword 

Geographic information, also known as geospatial information, both underlies and is the subject 

of much of the political, economic, environmental, and security activities of the United States. In 

recognition of this, the United States Office of Management and Budget issued Circular A-16 

(revised 2002), which established the Federal Geographic Data Committee (FGDC) as a 

coordinating organization. 

Work on this standard started under the Geospatial One-Stop e-Government initiative. The 

standard was developed with the support of the member agencies and organizations of the 

FGDC and aids in fulfilling a primary objective of the National Spatial Data Infrastructure (NSDI), 

that is, creation of common geographic base data for seven critical data themes. The seven core 

data themes are considered framework data of critical importance to the spatial data 

infrastructure. 

As the Geographic Information Framework Data Content Standard was developed using public 

funds, the U.S. Government will be free to publish and distribute its contents to the public, as 

provided through the Freedom of Information Act (FOIA), Part 5 United States Code, Section 552, 

as amended by Public Law No. 104-231, “Electronic Freedom of Information Act Amendments of 

1996”. 
Federal Geographic Data Committee FGDC-STD-014.4-2008 

Geographic Information Framework Data Content Standard 

Part 4: Geodetic Control

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Introduction 

The primary purpose of this part of the Geographic Information Framework Data Content 

Standard is to support the exchange of geodetic control data. This part seeks to establish a 

common baseline for the semantic content of geodetic control databases for public agencies and 

private enterprises. It also seeks to decrease the costs and simplify the exchange of geodetic 

control data among local, Tribal, State, and Federal users and producers. That, in turn, 

discourages duplicative data collection. Benefits of adopting this part of the standard also include 

the long-term improvement of the geospatial geodetic control data within the community. 

The Geographic Information Framework Data Content Standard, Part 4: Geodetic Control was 

developed with a certain philosophy which includes the following concepts: 

• Keep it simple; have the fewest data elements possible, but make those data elements 

mandatory. This encourages use of the part. 

• Anticipate which data elements surveying and mapping organizations, at all levels of 

government, have readily available. Again, this encourages use of the part. 

• Use single data types, for example, coordinate types. Different organizations store their 

data or make them available using a variety of data types, for example, latitude longitude, 

State Plane coordinates, UTM coordinates, elevations in meters, elevations in feet, and 

so on. Because the data provider, the organization creating the data, is the one most 

knowledgeable about their data, they should be responsible for converting their data into 

this single data type. Multiple data types would make the part less useful to data users. 

The rationale for this concept is based on the availability of tools, validated through the 

Federal Geographic Data Committee/Federal Geodetic Control Subcommittee, for 

converting other types of horizontal coordinate values to latitude-longitude. 

• Although geospatial data users often associate geodetic control coordinates with the 

highest accuracy coordinates attainable, there is no threshold set in this part for the 

accuracy of geodetic control coordinates, but the accuracy of the coordinates is a 

required data element. 

• Make the part compatible with current GIS software so data users do not have to convert 

the data to import them into their systems. 

• Require metadata supporting how the coordinates were derived and how their 

corresponding accuracy values were estimated. 

As stated in FRAMEWORK – Introduction and Guide, National Spatial Data Infrastructure, FGDC, 

1997 (p. 18): 

“Geodetic control provides a common reference system for establishing the coordinate positions 

of all geographic data. It provides the means for tying all geographic features to common, 

nationally used horizontal and vertical coordinate systems. The main features of geodetic control 

information are geodetic control stations. These monumented points (or in some cases active 

Global Positioning System control stations) have precisely measured horizontal or vertical 

locations and are used as a basis for determining the positions of other points. The geodetic 

control component of the framework consists of geodetic control stations and related information 

– the name, feature identification code, latitude and longitude, orthometric height, ellipsoid height, 

and metadata for each station. The metadata for each geodetic control point contains descriptive 

data, positional accuracy, condition, and other pertinent characteristics for that point. 

Geodetic control information plays a crucial role in developing all framework data and users’ 

applications data, because it provides the spatial reference source to register all other spatial 

data. In addition, geodetic control information may be used to plan surveys, assess data quality, 

plan data collection and conversion, and fit new areas of data into existing coverages.” 
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The Federal Geodetic Control Subcommittee (FGCS) of the Federal Geographic Data Committee 

was established to promote standards of accuracy and currentness in geodetic data financed in 

whole or part by Federal funds; to exchange information on technological improvements for 

acquiring geodetic data; to encourage the Federal and non-Federal communities to identify and 

adopt standards and specifications for geodetic data; and to collect and process the requirements 

of Federal and non-Federal organizations for geodetic data. The lead agency responsible for the 

coordination, management, and dissemination of geodetic data is the Department of Commerce, 

National Oceanic and Atmospheric Administration, National Ocean Service, National Geodetic 

Survey. 
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Part 4: Geodetic Control

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1 Scope, purpose, and application 

1.1 Scope 

Geodetic control surveys are usually performed to establish the basic positional framework from 

which supplemental surveying and mapping are performed. Geodetic control surveys are 

distinguished by use of redundant, interconnected, permanently monumented control points that 

comprise the National Spatial Reference System (NSRS) or are often incorporated into NSRS. 

Geodetic control surveys are performed to far more rigorous accuracy and quality assurance 

standards than those for local control surveys for general engineering, construction, or 

topographic mapping purposes. Geodetic control surveys included in NSRS meet automated 

data recording, submittal, project review, and least squares adjustment requirements established 

by the Federal Geodetic Control Subcommittee (FGCS). 

1.2 Purpose 

This document provides a common methodology for creating datasets of horizontal coordinate 

values and vertical coordinate values for geodetic control points represented by survey 

monuments, such as brass disks and rod marks. It provides a single data structure for relating 

coordinate values obtained by one geodetic survey method (for example, a classical line-of-sight 

traverse) with coordinate values obtained by another geodetic survey method (for example, a 

Global Positioning System geodetic control survey). 

1.3 Application 

This part of the Framework Data Content Standard is applicable to any geodetic control dataset 

and is intended to facilitate a common methodology to create, manage, and share geodetic 

control datasets from various organizations at the Federal, State, Tribal, and local government 

levels; academia; and the private sector. 

Although this part does not encompass non-geodetic control points, such as Public Land Survey 

System points, local government control points, project control points for public and private 

projects, aerial-photo control points, and so on, it can be used as a model for other control points 

and coordinated points (see Annex D). 

2 Normative references 

Annex A lists normative references applicable only to the Geodetic Control part. Annex A of the 

Base Document (Part 0) lists normative references applicable to two or more parts of the 

standard. Informative references applicable only to the Geodetic Control part are listed in Annex 

E. Annex D of the Base Document lists informative references applicable to two or more of the 

parts. 

3 Maintenance authority 

3.1 Level of responsibility 

The FGDC is the responsible organization for coordinating work on all parts of the Geographic 

Information Framework Data Content Standard. The U.S. Department of Commerce, National 

Oceanic and Atmospheric Administration, National Ocean Service, National Geodetic Survey, 

working with the FGDC, is directly responsible for development and maintenance of the 

Geographic Information Framework Data Content Standard, Part 4: Geodetic Control. 
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Part 4: Geodetic Control

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3.2 Contact information 

Address questions concerning this part of the standard to: 

Federal Geographic Data Committee Secretariat 

c/o U.S. Geological Survey 

590 National Center 

Reston, Virginia 20192 USA 

Telephone: (703) 648-5514 

Facsimile: (703) 648-5755 

Internet (electronic mail): gdc@fgdc.gov

WWW Home Page: http://fgdc.gov

Or 

Director 

National Geodetic Survey, NOAA, N/NGS 

1315 East-West Highway 

Silver Spring, Maryland, 20910-3282. 

4 Terms and definitions 

Definitions applicable to the Geodetic Control part are listed below. More general terms and 

definitions can be found in the Base Document (Part 0). Users are advised to consult that part for 

a complete set of definitions. 

4.1 

control point 

high-accuracy coordinated point used in determining the location of other points 

4.2 

coordinated point 

point with location defined by coordinates 

4.3 

geodetic control 

set of control points whose coordinates are established by geodetic surveying methodology 

EXAMPLE classical line-of-sight triangulation, traverse, and geodetic leveling or satellite 

surveys such as Doppler or GPS 

4.4 

geodetic datum 

datum describing the relationship of a coordinate system to the Earth [ISO 19111] 

4.5 

horizontal geodetic control 

control points for which horizontal coordinates that have been accurately determined can be 

identified with physical points on the Earth and used to provide horizontal coordinates for other 

surveys 
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Part 4: Geodetic Control

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4.6 

local accuracy 

correctness of the coordinates of a control point relative to the coordinates of other directly 

connected, adjacent control points

NOTE The reported local accuracy is an approximate average of the individual local accuracy values 

between this control point and other observed control points used to establish the coordinates of the control 

point. 

4.7 

National Spatial Reference System 

NSRS 

control framework for latitude, longitude, height, scale, gravity, orientation, and shoreline 

throughout the United States, comprised of coordinates of geodetic control points and models 

describing geophysical processes 

4.8 

network accuracy 

correctness of the coordinates of a control point with respect to the geodetic datum

NOTE For NSRS network accuracy classification, the datum is considered to be best expressed by the 

geodetic values at the Continuously Operating Reference Stations (CORS) supported by the National 

Geodetic Survey (NGS). By this definition, the local and network accuracies at CORS sites are considered 

to be infinitesimal, that is to say, to approach zero. 

4.9 

North American Datum of 1983 

NAD 83 

horizontal and 3-dimensional geodetic datum for the United States, Canada, Mexico, and Central 

America, based on the Geodetic Reference System 1980 ellipsoid and derived from the 

adjustment of more than 250,000 horizontal geodetic control points 

4.10 

North American Vertical Datum of 1988 

NAVD 88 

orthometric height geodetic datum for the United States, Canada, and Mexico, based on a 

minimally-constrained adjustment of more than 750,000 vertical geodetic control points 

4.11 

relative accuracy 

accuracy that accounts for only random errors in a dataset 

NOTE For positional data, the general measure of relative accuracy is an evaluation of the random 

errors (that is, where systematic errors and blunders have been removed) in determining the positional 

orientation (for example, distance, azimuth, elevation) of one point or feature with respect to another. 

4.12 

reference ellipsoid 

ellipsoid of specified dimensions and associated with a geodetic reference system or a geodetic 

datum 

NOTE Coordinates given in this system are said to be with respect to the reference ellipsoid. 

Reference ellipsoids are most commonly ellipsoids of revolution (that is to say, have two of the three 

possible axes of equal length) and are sometimes called reference spheroids. 
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Part 4: Geodetic Control

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4.13 

vertical geodetic control 

control points with accurately determined orthometric heights and/or ellipsoidal heights identified 

with physical points on the Earth that can be used to provide elevations for other surveys 

5 Symbols, abbreviated terms, and notations 

The following symbols, abbreviations, and notations are applicable to the Geodetic Control part. 

Symbols, abbreviations, and notations applicable to multiple parts are listed in the Base 

Document (Part 0). 

CORS – Continuously Operating Reference Stations 

HARN – High Accuracy Reference Network 

NAVD88 – North American Vertical Datum of 1988 

URI – Uniform Resource Identifier 

6 Requirements 

6.1 General 

For the purpose of this part of the Federal Data Content Standard, each geodetic control point 

shall have four (4) basic elements. They are: 

• Designations 

• Coordinates 

• Accuracy 

• Geodetic datum 

Each element is described in detail in the following paragraphs. For an example, see Annex B. 

6.2 Designations 

Designations refer to three types of identifiers used for each point in the dataset: 1) a unique 

identifier (mandatory); 2) a descriptive identifier (optional); 3) a Uniform Resource Identifier (URI) 

(optional). 

6.2.1 Unique identifier 

A unique identifier for each point within a dataset shall be composed of two parts: 1) a permanent 

identifier and 2) a namespace. The permanent identifier can be the organization’s unique 

database identifier. The namespace is the organization’s identifier (for example, abbreviation) for 

the organization who assigned/maintains the permanent identifier. The unique identifier allows 

traceability of each data point back to the organization and to other data held by that organization 

about the point. For example, NGS has a multitude of information about each geodetic control 

point, but only the basic information conforming to this part need be contained in the produced 

dataset. 

NOTE For geodetic control datasets, the uniqueness of namespace is maintained by the National 

Geodetic Survey through Input Format and Specifications of the National Geodetic Survey Data Base, 

Appendix C - Contributors of Geodetic Control Data, FGCS, 1994. 

If an organization has separate components, each providing its own datasets, the namespace 

shall be unique within that organizational element. For example, the U.S. Army Corps of 

Engineers has several districts. The permanent identifier shall be unique within a particular 

district, and each district shall have its own organizational identifier. The combination of the 

permanent identifier and the namespace provides for a truly unique identifier. 
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Part 4: Geodetic Control

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6.2.2 Descriptive identifier 

A descriptive identifier, such as the designation/point name or stamping which provides the user 

with a more meaningful name for the point, facilitates certain interactions with the point, for 

example, an understanding of what to physically look for in the field. Descriptive identifiers do not 

have to be unique within a dataset. 

6.2.3 URI 

A permanent URI, such as a URL, which provides the user with a direct link to an Internet-based 

resource that facilitates certain interactions with the point, for example, a link to an NGS 

datasheet or a scanned tie-sheet image. URI do not have to be unique within a dataset. 

6.3 Coordinates 

6.3.1 General 

Coordinates are of two types: horizontal and vertical. If only approximate values are present, 

they shall be used with their corresponding accuracies. 

Data providers shall provide the best set of coordinates available at the time of the request, but 

coordinates could change in the future based on improved, that is to say, more accurate, 

observational techniques. Data users are encouraged to be cautious and use the latest set of 

coordinate values. Typically geodetic coordinates do not change by more than their stated 

network accuracy. 

6.3.2 Horizontal coordinates 

The curvilinear system of latitude and longitude is required. Latitudes shall be referenced as 

positive north and negative south. Longitudes shall be referenced as positive east and negative 

west. If only an approximate value is available, use it along with its corresponding accuracy. The 

mandatory unit for latitude and longitude is decimal degrees. 

6.3.3 Vertical coordinates 

6.3.3.1 General 

Vertical coordinates consist of two types, orthometric height and ellipsoid height. Either 

orthometric or ellipsoid height shall be provided, and both shall be provided if both are measured. 

If only approximate values are available, provide at least one, along with its corresponding 

accuracy. The mandatory unit for height values is meters. 

6.3.3.2 Orthometric height 

Orthometric height shall be provided if measured, for example, by precise optical or electronic bar 

code leveling; vertical angle; or GPS. 

6.3.3.3 Ellipsoid height 

Ellipsoid height shall be provided if measured, for example, by GPS. 
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Part 4: Geodetic Control

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Figure 1 – Relationship between orthometric, ellipsoidal, and geoid heights 

6.4 Accuracy 

Local and network accuracies shall be provided in meters, expressed at the 95% confidence 

level. See FGDC-STD-007.2, Geospatial Positioning Accuracy Standards, Part 2: Geodetic 

Control Networks, for the methodology for defining local and network accuracies. 

NOTE See Annex C for guidance on estimating local and network accuracy values for geodetic control 

established using the older (for example, first order) methodology. 

6.5 Geodetic datum 

6.5.1 General 

Horizontal coordinates and ellipsoid heights shall be referenced to the North American Datum of 

1983 (NAD 83) and shall include the datum tag (for example, “NAD 83 (1986)”) and the 

coordinate epoch date (for example, “[1997.0]”), for example, “NAD 83 (1986) [1997.0]”. See also 

the Federal Register Notice, 1989. 

Orthometric heights shall be referenced to the North American Vertical Datum of 1988 (NAVD 

88). See also the Federal Register Notice, 1993. 

6.5.2 Datum tag 

The datum tag represents the date of the regional least squares adjustment associated with the 

horizontal geodetic control point. NAD 83 (1986) indicates horizontal coordinate values and 

ellipsoid height values on the NAD 83 datum resulting from the North American Adjustment 

completed in 1986. NAD 83 (ccyy) indicates coordinate values on the NAD 83 datum for the 

North American Adjustment, but readjusted to a State or regional High Accuracy Reference 

Network (HARN) during the year shown in parentheses (ccyy). See Annex B for an example. 

6.5.3 Epoch date 

The epoch date shall be used for control points in regions of episodic and/or continuous 

horizontal and vertical crustal motion where the coordinates change with time. The epoch date 

indicates the date the published horizontal coordinates and heights are valid. All points with 

adjusted horizontal coordinates and/or heights that fall within a crustal motion region shall have 

an epoch date based on the date of the latest survey from which the coordinates were 

determined. Points outside crustal motion regions shall not have an epoch date. 
Federal Geographic Data Committee FGDC-STD-014.4-2008 

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Part 4: Geodetic Control

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7 Geodetic control Unified Modeling Language (UML) model 

7.1 Unified Modeling Language (UML) class diagram 

Figure 2 – Geodetic control UML model
Federal Geographic Data Committee FGDC

Geographic Information Framework Data Content Standard Part 4: Geodetic Control

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7.2 UML objects 7.2.1 ControlPoint ControlPoint is a class that contains the identifier for the point (see 6.2.1), information about horizontal coordinaccuracy (see 6.4), and datum (see 6.5). ControlPoint also contains a link to a resource for the point (see 6.2.3)an association with the UML class VerticalInformation. Each geodetic location shall carry at least one height va

both orthometric and ellipsoidal height values. 

Table 1 – Data dictionary for ControlPoint 

Line Name/Role Name Definition Obligation/ Condition Maximum Occurrence Data Type 

1 ControlPoint <<Feature>> 2 uniqueID 

Permanent identifier can be the organization’s unique database identifier 

M 1 <<DataType>> Framework::Identifier 

3 horizontalPosition Position of horizontal coordinates for the control point M 1 <<Type>> GM_Point 4 localHorizontalAccuracy Local horizontal accuracy for the control point M 1 <<Abstract>> Data quality information

DQ_PositionalAccuracy 

5 networkHorizontalAccuracy Network horizontal accuracy for control point M 1 <<Abstract>> Data quality information

DQ_PositionalAccuracy 

6 horizontalReferenceSystem Information about referenceSystem, namely, datum M 1 Aggregated Class MD_CRS 7 link 

Identification of an external resource that provides documentation for the point 

O 1 

<<DataType>> Framework:: ExternalResource 

8 attribute Producer-defined attribute for inclusion in the transfer O * <<DataType>> Framework:: ExtendedAttribute 9 Role name: vertical Relationship with VerticalInformation M 2 <<DataType>> VerticalInformation 
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7.2.2 VerticalInformation VerticalInformation is a class that contains information about vertical coordinates associated with ControlPoint, inc

height (see 6.3.3), accuracy (see 6.4), and datum (see 6.5). This class also contains an association with ControlP

Table 2 – Data dictionary for VerticalInformation 

Line Name/Role Name Definition Obligation/ Condition Maximum Occurrence Data Type 

10 VerticalInformation <<DataType>> 11 height Distance above or below datum M 1 <<Type>> DirectPosition 12 /heightType 

Indicator if height is ellipsoidal or orthometric (although this information is inferred from the datum). This attribute is derived 

M 1 <<CodeList>> HeightType 

13 derived Indicator if the MD_CRS is derived (true) or referenced (false) M 1 Boolean 14 localVerticalAccuracy Local vertical accuracy for the control point M 1 <<Abstract>> Data quality information

DQ_PositionalAccuracy 

15 networkVerticalAccuracy Network vertical accuracy for control point M 1 <<Abstract>> Data quality information

DQ_PositionalAccuracy 

16 verticalReferenceSystem Information about referenceSystem, namely, datum M 1 VerticalCRS 17 Role name: controlPoint Relationship to control point M 1 <<Feature>> ControlPoint 
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7.2.3 RS_Identifier RS_Identifier is a class that contains information about the namespace used for the reference system, namely the 

Table 3 – Data dictionary for RS_Identifier 

Line Name/Role Name Definition Obligation/ Condition Maximum Occurrence Data Type 

18 Reference system information:: RS_Identifier Identifier used for reference systems <<DataType>> 19 codeSpace 

Name or identifier of the person or organization responsible for maintenance of the namespace 

O 1 CharacterString 

20 version Version identifier for the namespace O 1 CharacterString 
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Part 4: Geodetic Control 

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7.3 HeightType code list 

HeightType is a CodeList of values for the attribute heightType. 

Table 4 – CodeList for HeightType 

Name Definition 

ellipsoidal Distance of a point from the ellipsoid measured along the perpendicular 

from the ellipsoid to this point 

orthometric 

Distance measured along the plumb line between the geoid and a point on 

the Earth’s surface, taken positive upward from the geoid [adapted from 

the National Geodetic Survey, 1986] 
Federal Geographic Data Committee FGDC-STD-014.4-2008 

Geographic Information Framework Data Content Standard 

Part 4: Geodetic Control 

Annex A (normative): Normative references 

12

Annex A 

(normative) 

Normative references 

This annex lists normative standards that support only this part of the Framework Data Content 

Standard. Annex A of the Base Document (Part 0) lists normative references applicable to two or 

more parts of the standard. 

ANSI and ISO standards may be purchased through the ANSI eStandards Store at 

http://webstore.ansi.org/ansidocstore/default.asp, accessed October 2006. 

FGDC-STD-007.2-1998, Geospatial positioning accuracy standards, Part 2: Standards for 

geodetic networks, http://www.fgdc.gov/standards/projects/FGDC-standardsprojects/accuracy/part2/index_html/?searchterm=Geospatial%20positioning%20accuracy%20sta

ndards,%20Part%202:%20Standards%20for%20geodetic%20networks, accessed October 2006 

Federal Register Notice – Affirmation of datum for surveying and mapping activities; June 13, 

1989 (NAD 83) 

Federal Register Notice – Affirmation of vertical datum for surveying and mapping activities; June 

23, 1993 (NAVD 88)
Federal Geographic Data Committee FGDC-STD-014.4-2008 

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Part 4: Geodetic Control 

Annex B (informative): Example of geodetic control data content 

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Annex B 

(informative) 

Example of geodetic control data content 

Below are example values for geodetic control. 

uniqueID = MN0298 

uniqueIDAssigner = NGS 

descriptiveID = PUMKIN 

URI = http://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=MN0298 

coordinates – horizontal – latitude = 41.583365925 

coordinates – horizontal – longitude = -103.664305564 

coordinates – horizontal – accuracy – local = 0.046 

coordinates – horizontal – accuracy – network = 0.066 

coordinates – horizontal – geodeticDatum – baseDatum = NAD 83 

coordinates – horizontal – geodeticDatum – datumTag = 1995 

coordinates – horizontal – geodeticDatum – epochDate = 1997.0 

coordinates – vertical – orthometricHeight =1365.195 

coordinates – vertical – orthometricHeight – accuracy – local = 0.002 

coordinates – vertical – orthometricHeight – accuracy – network = 0.100 

coordinates – vertical – orthometricHeight – geodeticDatum – baseDatum = NAVD 88 

coordinates – vertical – orthometricHeight – geodeticDatum – datumTag = none 

coordinates - vertical – orthometricHeight – geodeticDatum – epochDate = 2003.0 

coordinates – vertical – ellipsoidHeight = 1346.13 

coordinates – vertical – ellipsoidHeight – accuracy – local = 0.064 

coordinates – vertical – ellipsoidHeight – accuracy – network = 0.127 

coordinates – vertical – ellipsoidHeight – geodeticDatum – baseDatum = NAD 83 

coordinates – vertical – ellipsoidHeight – geodeticDatum – datumTag = 1995 

coordinates – vertical – ellipsoidHeight – geodeticDatum – epochDate = 1997.0 
Federal Geographic Data Committee FGDC-STD-014.4-2008 

Geographic Information Framework Data Content Standard 

Part 4: Geodetic Control 

Annex C (informative): User guidance for estimating local and network accuracy values 

14

Annex C 

(informative) 

User guidance for estimating local and network accuracy values 

Local accuracy for horizontal and vertical geodetic control points is similar to the older accuracy 

methodology, since they are both methods to describe the relative accuracy between points. 

Hence, the older methodology can be converted into local accuracy by taking the average length 

of line, using the older defined accuracy of the points, and converting that into a value in meters. 

Examples for horizontal and vertical surveys are: 

• Second-order, class II horizontal survey (that is to say, 1:20,000) with average length line 

of 3,500 meters: 3,500 x 1/20,000 = 0.175 meters 

• Second-order, class II leveling survey (that is to say, 1.3 millimeters per square-root of 

the distance in kilometers) with an average bench mark spacing of 1 mile (that is to say, 

1.6 kilometers): 0.0013 x SQRT [1.6] = 0.0016 meters 

Network accuracy for horizontal geodetic control points can be estimated in two ways. First, if the 

NAD 83 coordinates are consistent with the original NAD 83 adjustment, for example, the original 

NAD 83 (1986), then the network accuracy has been determined to seldom exceed 1.0 meters. 

Second, if the NAD 83 coordinates are the result of a statewide or regional High Accuracy 

Reference Network (HARN) adjustment, then the network accuracy has been determined to 

seldom exceed 0.05-0.1 meter. If better values have been determined for network accuracy for 

the area covered by the specific dataset, then those values should be used in place of these 

general values. 
Federal Geographic Data Committee FGDC-STD-014.4-2008 

Geographic Information Framework Data Content Standard 

Part 4: Geodetic Control 

Annex D (informative): Control points and coordinated points 

15

Annex D 

(informative) 

Control points and coordinated points 

There are various categories of points that are described with coordinates. The most general 

category is coordinated points which can be any point on the ground or on a map for which 

coordinates have been determined. There are also many methods for determining the 

coordinates of these points. A subset category of coordinated points is control points. Control 

points have several common characteristics: 

• They are physical points on the ground which can be revisited or located for future use 

• They are used for subsequent projects, that is to say, they themselves are not the end 

product 

• Their coordinates are determined using more accurate techniques because they will be 

used to control or fit future spatial data activities 

Geodetic control is one type or category of control points. 

This part can be expanded with additional elements to make it fit the more general class of 

control points. For example, one attribute that could be added is control point TYPES. Some 

examples of these TYPES are: 

• NSRS – geodetic control points whose coordinates have been verified and placed in a 

national database 

• PLSS – Public Land Survey System points whose coordinates have been determined 

• Property corner – lot or property points, non-PLSS, whose coordinates have been 

determined 

• Photo control – photographic identifiable points set for aerial photography whose 

coordinates have been determined 

• Right-of-way – right-of-way points whose coordinates have been determined 

• Local control – random control points whose coordinates have been determined that are 

not multi-functional (that is to say, established for a single use) and are not NSRS 

Because the subject of control points involves almost every FGDC subcommittee, the task of 

developing a data content standard for all control points is much more involved than for geodetic 

control alone. 
Federal Geographic Data Committee FGDC-STD-014.4-2008 

Geographic Information Framework Data Content Standard 

Part 4: Geodetic Control 

Annex E (informative): Bibliography 

16

Annex E 

(informative) 

Bibliography 

The following documents contain provisions that are relevant to this part of the Framework Data 

Content Standard. Annex D of the Base Document (Part 0) lists informative references 

applicable to two or more of the parts of the standard. For dated references, only the edition cited 

applies. For undated references, the latest edition of the referenced document applies. 

ANSI and ISO standards may be purchased through the ANSI eStandards Store at 

http://webstore.ansi.org/ansidocstore/default.asp, accessed October 2006. 

Federal Geodetic Control Subcommittee, FGDC, Input formats and specifications of the National 

Geodetic Survey Data Base, FGCS, 2003, Silver Spring, MD, 

http://www.ngs.noaa.gov/FGCS/BlueBook/pdf/hContents.pdf, accessed October 2006