[Federal Register Volume 85, Number 143 (Friday, July 24, 2020)]
[Notices]
[Page 44865]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-16084]



[[Page 44865]]

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration


Consideration of Potential Age-Limiting Observations To Be Used 
To Compute 2020.00 Reference Epoch Coordinates in the National Spatial 
Reference System

AGENCY: The Office of the National Geodetic Survey (NGS), National 
Ocean Service (NOS), National Oceanic and Atmospheric Administration 
(NOAA), Department of Commerce (DOC).

ACTION: Request for information.

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SUMMARY: The National Geodetic Survey (NGS) is considering imposing age 
limits on the observations that will be used in the creation of 2020.00 
Reference Epoch Coordinates (RECs), as part of the modernization of the 
National Spatial Reference System (NSRS). Due to expected uncertainties 
in the vertical component of the Intra-Frame Velocity Model (IFVM), the 
age limits cannot be determined until well-structured, data-driven 
experiments have been conducted. Such experiments are expected to occur 
during the 2020 reference epoch adjustment projects (geometric, 
orthometric and gravimetric), which are scheduled for calendar year 
2022. Therefore, NGS requests that users take new Global Navigation 
Satellite System (GNSS) observations on geodetic control marks of 
interest, especially those marks that have not been surveyed since 
January 1, 2010, and share them with NGS before December 31, 2021.

DATES: The effective date of this announcement is upon publication of 
this notice. Submission of GNSS observations on geodetic control marks 
of interest are requested before December 31, 2021.

ADDRESSES: National Geodetic Survey, 1315 East-West Highway, Silver 
Spring, MD 20910.

FOR FURTHER INFORMATION CONTACT: Dr. Dru Smith, NSRS Modernization 
Manager, by email at [email protected], by phone at (240) 533-9654, or 
by mail at NOAA/NOS/NGS 1315 East-West Highway, Silver Spring, MD, 
20910.

SUPPLEMENTARY INFORMATION: In 2017, the National Geodetic Survey (NGS) 
announced its plans to estimate RECs on a five-year cycle in NOAA 
Technical Report NOS NGS 67, 2019, starting with the first reference 
epoch at 2020.00, as part of the modernization of the NSRS. In the 
Technical Report, the exact observations to be used for this estimation 
were listed as ``To Be Determined.'' Now, NGS is considering imposing 
age limits upon the observations that will be used, particularly 
because of expected uncertainties in the vertical component of the 
IFVM. These age limits cannot be determined until additional well-
structured, data-driven experiments are conducted. Such experiments are 
expected to occur during the 2020 reference epoch adjustment projects 
(geometric, orthometric, and gravimetric), which are scheduled for 
calendar year 2022.
    However, since the cut-off for new observations to enter those 
adjustment projects is December 31, 2021, any decision to age-limit 
input observations will come too late for submissions to impact the 
2020 RECs. While the cut-off for age-limited observations is unknown, 
certain assumptions are safe to make. For instance, it is unlikely that 
such an age-limit will be fewer than 10 years. Older observations may 
be used in the estimation of 2020 RECs, but this cannot be guaranteed. 
As such, NGS requests that users take new GNSS observations on geodetic 
control marks of interest that have not been surveyed since January 1, 
2010, and asks the users to submit the observations to NGS before 
December 31, 2021. Users may either (a) submit existing unsubmitted 
observations through the OPUS-Share tool or (b) conduct new GNSS 
observations and submit the data to NGS via the OPUS-Share tool.
    In order to increase the submission of GNSS observations on marks, 
NGS is prioritizing the finalization of an expanded OPUS-Projects tool, 
which will allow real-time kinematic and real time network (RTK/RTN) 
observations to be submitted, rather than the standard four-hour 
observations required in OPUS-Share. Initial roll-out of this new tool 
is expected to occur during calendar year 2020.
    This action is designed to increase both the number and the 
coordinate accuracy of geodetic control points, which in the modernized 
NSRS will have an estimated 2020.00 REC. Historically, NGS has combined 
data across multiple decades to estimate geodetic coordinates, yet such 
efforts have not fully accounted for the lack of information about 
vertical motion of geodetic control points throughout the years. Since 
height information is critical to the understanding of floods, failure 
to compute heights accurately can have negative impacts on property and 
lives. NGS views periodic re-surveys of geodetic control points, rather 
than the estimation of coordinates from observations that are years (or 
even decades) old, as the most effective way to maintain accurate and 
up-to-date knowledge of geodetic coordinates, including heights. As 
such, this announcement provides users of the NSRS with advance notice 
that geodetic control points of interest to them should be re-surveyed 
for the most accurate representation of geodetic coordinates, including 
heights.

    (Authority: Coast and Geodetic Survey Act of 1947, 33 U.S.C. 
883a et seq.)

Juliana P. Blackwell,
Director, National Geodetic Survey, National Ocean Service, National 
Oceanic and Atmospheric Administration.
[FR Doc. 2020-16084 Filed 7-23-20; 8:45 am]
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