INTRODUCTION
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.
MISSION
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.
MEMBERSHIP
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.
OPERATING PROCEDURES
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.
Administration
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.