Safe and 

efficient 

transportation 

and commerce

NOS Priority: 

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2021 NOS SCIENCE REPORT

S

HIPS MOVE $1.5 TRILLION worth of products 

in and out of U.S. ports every year. Every 

ship moving in and out of U.S. ports relies on 

navigation charts and water level information 

that NOS alone provides. All mapping, charting, 

and transportation activities and infrastructure 

are founded on a reliable, accurate national 

coordinate system. NOS is solely responsible for 

maintaining that system, which provides more than 

$2.4 billion in potential annual benefits to the U.S. 

economy. Businesses in the maritime community 

rely on NOS for a range of decisions, from how 

much cargo to load to choosing the safest and 

most efficient route between two points. They use 

NOS data, tools, and services to plan seasonally 

for ship schedules to service global trade more 

safely and efficiently as significantly larger vessels 

transit through U.S. ports.

Following are transportation and commerce 

themed projects organized according to two 

primary scientific priorities of the National 

Centers for Coastal Ocean Science (NCCOS) 

strategic plan.
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2021 NOS SCIENCE REPORT Safe and Efficient Transportation and Commerce

Advanced Observation 

Technologies

Included below are nine highlighted scientific 

projects by NGS, OCS, and IOOS researchers and 

their partners, which are focused on advanced 

observation technologies.

Determining the Rotation of the Mariana 

tectonic plate

In a few years, NGS will modernize the National 

Spatial Reference System (NSRS). This system will 

include the definition of a plate-fixed reference 

frame for Guam and the Commonwealth of the 

Northern Mariana Islands (CNMI) called the 

Mariana Terrestrial Reference Frame of 2022 

or MATRF2022. To define such a frame, the 

absolute rotation of the underlying tectonic plate 

(Mariana) must be known relative to a global 

plate-independent frame, such as the International 

Terrestrial Reference Frame. Very few studies of 

the Mariana plate have ever been performed, 

and most are only relative to other plates. To 

address this situation, NGS in 2017 performed a 

complicated GPS survey of geodetic control points 

on numerous islands on the plate. This survey 

collected data on points that had been previously 

surveyed by GPS between 2003 and 2014. By 

differencing these various surveys, linear velocities 

were implied and subsequently used to define the 

rotation of the plate. This estimate of the plate’s 

rotation was the most accurate and data-rich 

estimate ever performed for this small tectonic 

plate and will serve as the underlying model for 

MATRF2022. The results were published in the 

NOAA Technical Report series in August 2020.

FY21 ACCOMPLISHMENT: 

Peer reviewed publication in the NOAA Technical 

Report series quantifying the absolute rotation of 

the Mariana plate.

NOAA Technical Memorandum: https://geodesy.noaa.gov/library/pdfs/NOAA_TR_NOS_

NGS_0074.pdf

GPS-implied 

velocities on the 

Mariana plate 

(left), and some 

of the ground 

truth surveys 

which generated 

them in Maug 

(top right) and 

Alamagan 

(bottom right), 

CNMI. 

Image credit: NOAA/NOS/NGS.
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2021 NOS SCIENCE REPORT Safe and Efficient Transportation and Commerce

Machine Learning Applications for the 

Effective Operation of Autonomous 

Surface Vessels in Ocean Mapping 

Missions

In FY 2021, the NOAA/University of New 

Hampshire Joint Hydrographic Center and Center 

for Coastal and Ocean Mapping Autonomous 

Surface Vessel (ASV) Team, together with OCS, 

achieved significant improvements in the use of 

Machine Learning for ASV operations. The team 

has developed a software framework based 

on the Robotics Operating System, integrating 

cameras, swath mapping echo-sounders, marine 

radar, lidar, marine automatic identification service 

(AIS), National Marine Electronics Association 

(NMEA) based sensors for engine monitoring and 

vehicle health. The software framework builds on 

the open source nature of ROS with algorithms 

for object detection and classification and system 

control and includes a custom operator’s interface 

and map-based mission planning software. Its 

modular architecture allows for rapid integration 

of new algorithms and technologies into robotic 

vessels and for collaboration and sharing of those 

algorithms with others. 

The Joint Hydrographic Center uncrewed 

surface vessel underway off Portsmouth, 

New Hampshire. Image credit: NOAA/NOS/OCS.

FY21 ACCOMPLISHMENT: 

The program achieved significant improvements 

in autonomous surface vessel operation for 

hydrographic survey and ocean mapping.

Project URL: https://www.unh.edu/unhtoday/2021/01/seas-day

AWARDS:

The project team won first place in the Virtual 

Ocean Robotics Challenge (https://www.

oceanroboticschallenge.com) sponsored by Open 

Robotics, the Naval Post Graduate School and the 

Office of Naval Research.

Downward continuation of airborne gravity 

data for vertical datum determination

NGS is conducting a large-scale campaign, called 

Gravity for the Redefinition of the American 

Vertical Datum (GRAV-D), to collect airborne 

gravity data over wide areas at a nominal flight 

height of 6 km. This project started in 2007 

and has currently flown 86% of the U.S. and its 

territories. The flights also extend 100 km over the 

border into Mexico and Canada as well as into the 

open ocean areas. These newly acquired gravity 

data will serve as the backbone for computing 

the forthcoming vertical datum in North America 

(the North American-Pacific Geopotential Datum 

of 2022). How to downward continue the gravity 

data from flight trajectories to a reference ellipsoid 

surface, and how to render the 3D scattered data 

into a 2D grid with regular grid intervals, have 

been difficult problems in the field of physical 

geodesy for many decades. It is important to find 

the optimal solution to derive the best information 

from these aerial gravity data for the vertical 

datum computation. An NGS research geodesist 

has led an international working group within the 

International Association of Geodesy to tackle 

this problem. The group includes professors 

and scientists from numerous universities and 

agencies in the United States, Europe, Taiwan, 

and Canada. The working group has used both 

simulated data, and real GRAV-D data in the 

Colorado area, as a test bed to analyze various 

downward continuation methods. The resulting 

geoid models agreed at the mm-level, once data 

editing problems were addressed. The analysis 

also showed that there are spectrum leakage 

problems for some of the methods. The group 

developed high-performance-computation (HPC) 

software packages for comparing the six different 

methods, and these will be shared with the global 

geodetic community.
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2021 NOS SCIENCE REPORT Safe and Efficient Transportation and Commerce

Schematic of airborne data collection 

and software outputs for vertical datum 

determination. Image credit: NOAA/NOS/NGS.

FY21 ACCOMPLISHMENT: 

Established solid theoretical background to 

downward continue aerial gravity data for geoid 

modelling; developed HPC software to share; 

obtained 1mm model agreements from the 

different formulizations; found and fixed the 

spectral leakage problem in the current NGS 

operational tools.

Published Abstract: Li, X., Huang, J., Willberg, M., Pail, R., Slobbe, C., Klees, R., Forsberg, 

R., Hwang, C., and Hilla, S.: On Downward Continuing Airborne Gravity Data for Local 

Geoid Modeling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2706, 

https://meetingorganizer.copernicus.org/EGU21/session/39915

Multi-Constellation GNSS Calibration of 

User/Receiving Antennas at the National 

Geodetic Survey

Sub-centimeter positions with the Global Navigation 

Satellite System (GNSS) require modeling and 

correction for the electrical properties of the 

receiving antenna. Creating a correction table for 

the antenna’s electrical properties is called antenna 

calibration. Although NGS has calibrated GPS 

user antennas since 1994, recent acquisition and 

programming of a 6-axis industrial robotic arm (a 

device capable of achieving positions with submm accuracy) and tunable multi-GNSS receivers 

has allowed NGS to increase the capabilities 

of the antenna calibration program. The NGS 

calibration system has successfully demonstrated 

that it will be able to calibrate user antennas for 

all GNSS frequencies, with results that agree well 

with community standards. 

Top: KUKA 6-axis robotic arm, as installed 

at NGS’s Testing and Training Facility, with a 

chokering GNSS antenna mounted on the 

robot’s tool end. Bottom: The robotic arm 

is housed inside a retractable dome, and is 

pictured here with several antennas used to 

validate the system’s results. Image credit: NOAA/NOS/NGS.
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2021 NOS SCIENCE REPORT Safe and Efficient Transportation and Commerce

FY21 ACCOMPLISHMENT: 

Achieved multi-GNSS, full-spectrum calibrations 

with new high-accuracy 6-axis robotic arm.

Project URL: https://www.ngs.noaa.gov/ANTCAL/ 

AWARDS:

A previous, less accurate system using a 2-axis 

robot won a 2014 Bronze Medal “for the design 

and implementation of a NOAA absolute GPS/

GNSS antenna calibration program to improve 

GPS positioning accuracy for all users.”

Modeling Geoid Change in Alaska at 

Higher Resolution

NGS’ upcoming geopotential datum requires a 

dynamic component to ensure it matches the 

changing shape of the geoid—the level surface 

formed by Earth’s gravity that best describes 

mean sea level—with centimeter accuracy. 

NASA’s GRACE and GRACE-FO satellites have 

provided a record of changes to Earth’s gravity 

field due to ice mass loss, hydrology, and solidEarth processes. While they adequately capture 

these changes over most of North America, ice 

mass loss in Alaska changes the gravity field at 

much smaller scales than these satellites can 

resolve, resulting in errors of omission of more 

than 1 centimeter per decade. NGS scientists 

augmented the spatial resolution of the satellite 

models with predictions of geoid change derived 

from glacier elevation change measured with 

airborne altimetry and photogrammetry. These 

models were used to generate predictions of 

geoid change in southern Alaska since the 

mid-20th century that will be compared with 

historical gravity, elevation, and astronomical 

measurements.

FY21 ACCOMPLISHMENT: 

Created models of geoid change in Alaska with 

enhanced spatial resolution and developed and 

carried out a survey campaign to validate the 

models against historical measurements.

Presentation URL: https://www.ngs.noaa.gov/web/science_edu/presentations_library/

files/agu2019_hardy.pdf

New position time series, velocities and 

quality measures for the CORS Network

The NOAA Continuously Operating Reference 

Station (CORS) network is a volunteer-based 

network of Global Positioning System (GPS) 

reference stations located mainly in the US and its 

territories. NGS scientists have reprocessed all GPS 

data collected via this network since 1996. Daily data 

Left panel: A map of predicted geoid change in southern Alaska from ice mass loss with sites of 

historical gravity, elevation, and astronomical measurements. Right panel: NGS scientist collecting 

gravity measurements using a relative gravimeter during an Alaska survey. Image credit: NOAA/NOS/NGS.
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2021 NOS SCIENCE REPORT Safe and Efficient Transportation and Commerce

for GPS weeks 834 through 1933 were reprocessed 

leading to reference coordinates and velocities for 

3049 stations aligned to the global reference frame 

IGS14. The derived velocity field was compared 

to several other solutions and to three regional 

geophysical and geodetic velocity models. These 

comparisons uncovered unstable stations which 

move differently than the regional kinematics around 

them. Once these were identified and excluded, 

we estimated the horizontal and vertical stability 

of this updated realization to be better than ~0.3 

and ~0.6 mm/year, respectively. We used the 

position residuals and estimated uncertainties 

from this reprocessing to derive long-term stability 

measures for all active stations. These measures 

exposed ~60 CORS with the poorest long-term 

stability, which have been consequently excluded 

from serving as mapping control. 

FY21 ACCOMPLISHMENTS:

(1) The updated realization of the US National 

Spatial Reference System derived in this work is 

now officially in use; (2) This work was published 

in the Journal of Applied Geodesy in January 

2021; (3) The work is based on intensive use of 

estimation theory and statistical analysis and 

successfully incorporated concepts and in-house 

developed Artificial Intelligence tools: edge 

detection, cluster analysis and information theory.

Peer reviewed journal article: https://www.degruyter.com/document/doi/10.1515/jag2020-0041/html

NGS participation in the 3rd IGS 

reprocessing of GNSS data (REPRO3)

In early 2022, the International Earth Rotation and 

References Systems Service (IERS) will release 

the 2020 iteration of the International Terrestrial 

Reference Frame (ITRF2020). The forthcoming 

realization of ITRF2020 will combine observations 

from all of the major space geodetic techniques, 

including data from global navigation satellite 

systems (GNSS). The international body responsible 

for coordinating the GNSS contribution to 

ITRF2020 is the International GNSS Service (IGS). 

This effort by the IGS, completed in April 2021, 

was called the 3rd IGS reprocessing campaign. 

NGS is one of several IGS Analysis Centers (ACs) 

that participated in this campaign. To do so, we 

reprocessed all available GNSS data from 533 

global continuously operating reference stations 

for the period between January 1, 1994, through 

December 31, 2020. These data were reprocessed 

using the most up-to-date techniques and 

models to produce three primary products: daily 

ground station positions, daily Earth-orientation 

parameters, and daily precise orbit solutions. These 

products, representing 27 years of daily solutions, 

were then sent to the IGS and were combined 

with independently computed solutions from the 

other IGS ACs. The combined IGS daily solutions 

were then sent to the IERS to be incorporated into 

ITRF2020. ITRF2020, much like previous iterations 

Left panel: Major part of the NOAA CORS Network. Right panel: Velocity noise east of the Rockies 

(RMS ~0.2 mm/yr). Image credit: NOAA/NOS/NGS.
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2021 NOS SCIENCE REPORT Safe and Efficient Transportation and Commerce

of the ITRF, will form the backbone for all scientific 

positioning applications around the globe. It will 

also be the basis for the modernized U.S. National 

Spatial Reference System (NSRS), the official U.S. 

reference frame for all federal civilian applications. 

By participating in this campaign, NGS has ensured 

that there is superb representation of GNSS data 

from ground stations within the U.S. and our areas 

of interest (e.g. Caribbean, Pacific islands, etc.). This 

will allow NGS to very strongly tie the upcoming 

modernized NSRS to ITRF2020.

IGS ACs, including NGS, submitted 27 years 

of daily GNSS solutions to the IGS. The 

combined daily IGS solutions were then sent 

to the IERS for combination with solutions 

from the International Laser Ranging Service 

(ILRS), the International DORIS Service (IDS), 

and the International VLBI Service (IVS).

Image credit: NOAA/NOS/NGS.

FY21 ACCOMPLISHMENT: 

NGS reprocessed 27 years of daily GNSS 

solutions dating back to January 1, 1994. These 

solutions will contribute directly to the forthcoming 

ITRF2020 reference frame.

Precision Marine Navigation Data Gateway 

Viewer

NOAA and OCS have developed a web-mapping 

application that enables users to explore NOAA’s 

navigation datasets that are formatted based on 

international standards. The Data Gateway Viewer 

provides an easy-to-use, interactive resource for 

discovering NOAA’s navigation data products. 

Users can navigate to a region of interest, find the 

data that are available for that area, and access 

downloadable versions of the data in the cloud 

through the NOAA Big Data Program. It also 

uses new visualization techniques to make the 

data easy to comprehend. The beta version of 

the Data Gateway is one piece of NOAA’s larger 

effort to integrate marine navigation data services. 

The Data Gateway provides a visualization of 

the data NOAA is also serving via the cloud in a 

machine-to-machine readable format for software 

companies to utilize in various navigation software 

applications from portable pilot units to electronic 

charting systems and even mobile applications. 

The Data Gateway Viewer is an important tool 

Screen grab from the Precision Marine Navigation Data Gateway Viewer. Image credit: NOAA/NOS/OCS.
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2021 NOS SCIENCE REPORT Safe and Efficient Transportation and Commerce

for making the maritime community aware of 

NOAA’s navigation data, and it represents the 

continued commitment to ensure precision marine 

navigation in U.S. waters.

FY21 ACCOMPLISHMENT: 

A beta version of the Precision Marine Navigation 

Data Gateway Viewer was launched in January 

2021 that provides surface current forecast 

guidance (S-111 data).

Data Gateway Viewer Application URL: https://beta.marinenavigation.noaa.gov/gateway/

Data Gateway Viewer Press Release URL: https://nauticalcharts.noaa.gov/updates/

noaa-releases-new-visualization-resources-precision-navigation-data-gateway-and-datadashboard/

Short Term Predictive System (STPS) 

Enhancing Search-and-Rescue Nationwide 

with IOOS Oceanographic High Frequency 

Radar

In FY 2021 the Short Term Predictive System 

model (STPS) footprint expanded to cover the 

entire continental United States, Hawaii, and 

Puerto Rico. The model now assimilates data from 

newly added IOOS High-Frequency (HF) radar 

sites around the country into surface current 

forecasts for the U.S. Coast Guard’s (USCG) 

Search and Rescue Optimal Planning System 

(SAROPS) and also provides the framework 

to deliver data from future IOOS HF radar 

installations to the system. In 2000, the USCG 

Research & Development Center began a multiyear investigation into the utility of NOAA IOOS 

real-time HF radar surface current measurements 

for search and rescue. This assessment showed 

HF radar derived currents performed better 

when compared against available NOAA tidal 

current predictions. A team at the University of 

Connecticut, with IOOS funding, developed the 

STPS empirical statistical model to deliver these 

HF radar current forecasts; in May 2009 the 

STPS forecasts went live in the SAROPS for the 

mid-Atlantic, and later expanded to the U.S. West 

Coast in 2012.

FY 2021 ACCOMPLISHMENT:

The STPS ocean surface current forecast model 

expands to provide IOOS HF radar data nationwide 

for improving U.S. Coast Guard search-and-rescue.

Technical Paper: https://rucool.marine.rutgers.edu/media/downloads/papers/

National%20IOOS%20High%20Frequency%20Radar%20SAR%20Project.pdf

Schematic of the 

data pathways 

and components 

of the IOOS 

enhancements 

to the HF radar 

component of 

USCG SAROPS. 

The blue dotted 

lines enclose 

components that 

existed prior to 

the project. The 

enhancements 

are shown within 

the white dotted 

lines.

Image credit: NOAA/NOS/IOOS.
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2021 NOS SCIENCE REPORT Safe and Efficient Transportation and Commerce

Ecosystem Science for 

Conservation and Sustainable 

Use

Below is a highlighted scientific project by OCS 

researchers and their partners, which is focused 

on ecosystem science for conservation and 

sustainable use of coastal systems. 

Building the National Bathymetry

The National Bathymetry is a foundational dataset 

that supports the next-generation of navigation 

services as well as commerce, science, industry, 

and public curiosity. OCS compiles disparate 

hydrographic and LIDAR source surveys based 

on standard metrics like resolution, accuracy, 

survey date, and data license. In fiscal year 2020, 

the team built the New England dataset and 

that region is now being updated monthly as 

new sources are available. This year, the team 

is building out the National Bathymetry for the 

Gulf of Mexico region and work is underway to 

distribute products of this critical bathymetric 

compilation in various datum, formats, and 

resolutions. The establishment of a data-driven 

workflow through automation and expertise allows 

for increased quality, accessibility, and timeliness 

of bathymetric source data.

FY21 ACCOMPLISHMENT: 

The National Bathymetry is being built out for the 

Gulf of Mexico region while the already built New 

England region is regularly updated with newly 

available source surveys. 

Project URL: https://nauticalcharts.noaa.gov/updates/building-the-national-bathymetry/

 A preliminary build of the bathymetry for New England. Image Credit: NOAA/NOS/OCS.