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Vertical Reference Systems Work Group Charter


The NOAA National Geodetic Survey has implemented various vertical datums which impact a broad spectrum of users of the National Spatial Reference System (NSRS).  These include the North American Vertical Datum of 1988 (NAVD 88), and other more localized modern datums such as the Puerto Rico Vertical Datum of 2002 (PRVD 02) and the American Samoa Vertical Datum of 2002 (ASVD 02).  The Federal Geodetic Control Subcommittee (FGCS) has a special interest in and responsibility for "development and evaluation of geodetic data definitions and standards” and “establishment of surveying specifications to support [those] standards.”  This includes defining a consistent well-defined vertical reference frame and ways to access it.  Although FGCS has a wide range of representation it is recognized that there are other federal, state, local, and private sector interests in these new vertical datums that should also be considered.

Implementation of the new datums is still underway, as agencies and users continue to update their products.  Having access to a consistent vertical reference frame is crucial to meeting the current needs of the users of the NSRS, and enabling the transition to future technologies and datum determinations.  With the advancement of Global Positioning System (GPS) and other Global Navigation Satellite System (GNSS) technologies, as well as global gravity determination projects such as Gravity Recovery and Climate Environment (GRACE) and Gravity field and steady-state Ocean Circulation Explorer (GOCE), future definitions of the US National Vertical datum are being considered. The proper integration of Global Positioning System (GPS) and other Global Navigation Satellite System (GNSS) data, through programs and projects such as NOAA’s Height Modernization, FEMA’s Map Modernization, and the USACE  National Levee Database and Comprehensive Evaluation of Project Datums efforts into the vertical component of the NSRS is of utmost importance in order to continue to provide accurate, cost-effective vertical reference frame to the Nation.  The Vertical Reference System Work Group shall investigate and report on available information and recommend an overall strategy for the future role of GNSS and other technologies as it relates to vertical control surveys.


The first mission of this Work Group is to provide scientific advice and assistance to NOAA’s National Geodetic Survey in support of completing practical implementation from older to more contemporary vertical reference systems on a nation-wide scale. This includes making recommendations regarding what tools are needed to move the Nation to these new reference frames. One facet of this task will be to implement a National Height Modernization Program that will allow users of GNSS and geospatial data to obtain accurate orthometric heights using modern technologies in conjunction with traditional surveying techniques such as gravity observations and leveling.  The Group will provide information utilizing its own professional abilities, responsibilities, and contacts with users of geodetic data.  These contacts will include subject-matter specialists within their own departments and agencies.  Detailed approaches to accomplishing this mission will be determined by the Work Group.

The second mission of this Work Group is to monitor uses and users of the vertical component of the NSRS and of advanced technologies with the goal to anticipate future needs.  In the next 10 years, it is expected that there will be a need for another kind of vertical reference frame by users of spatial data.  Rather than wait till that transition is underway to develop the standards, specifications, guidelines, and tools to meet that need, this Work Group will discuss the possibilities and recommend ways to meet that need as it develops.


The Chair of this Work Group will be from NOAA, National Geodetic Survey and must posses an extensive, practical knowledge of vertical surveys and GNSS procedures.  Each member agency of FGCS may designate one or two employees to serve on this Work Group.  It is preferred that the Work Group members have a practical knowledge of classical vertical surveys and/or GNSS vertical related activities.  The Work Group Chair may propose additional Work Group members from non-FGCS Federal agencies as deemed appropriate.  The Chair shall be appointed by the FGCS Chair, with the concurrence of the agency representatives.


The Work Group shall meet as often as necessary, as but not less than twice each year, as directed by the Work Group Chair to consider directives from FGCS.  Normally, notification of meetings and an agenda will be distributed to members of the Subcommittee and to the Executive Secretary at least 14 days in advance of the meeting.

All decisions shall be on the basis of consensus agreement. Where agreement is not reached, the issue will be promptly referred to the FGCS Chair for resolution.

The Work Group Chairperson shall consult with the Chairperson of FGCS to determine the need for further coordination prior to implementing Work Group decisions that impact FGCS and FGDC or its other subcommittees or Work Groups.

The Work Group may establish additional rules and procedures for conducting business.
The Work Group will:
1. Collect information from users about their vertical reference system needs.
2. Consider and document the impact on users from changes in the vertical reference system.
3. Review existing vertical reference systems, including datum definition, data types, and estimates of precision and accuracy.
4. Develop improvements to strategies to incorporate modern technology information such as GNSS, and global gravity programs such as GRACE and GOCE, into vertical reference systems.
5. Recommend the appropriate course of action for NGS and other Federal agencies to take with regard to vertical reference frames.
6. Document and report the findings of the Work Group to the Chairperson, FGCS, for distribution to FGCS members.


The FGCS member agencies have supported the activities of these personnel while engaged in coordination functions; such support would be expected for the Work Group members. The Work Group Chair will generally arrange meeting sites, prepare the meeting agendas from the Group’s recommendations, prepare meeting notes and finalize reports.  The Chair may occasionally assign a member of the Group to assist with these functions.

Last Updated: Jul 15, 2008 10:24 AM
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