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  • The Future of the National Spatial Reference System
  • How the 2022 Datum Change will impact Louisiana
  • Louisiana's Terrestrial Gravity Studies 
  • GEOID model Improvements for Louisiana
  • Louisiana State NSRS Legislation
  • Expert Panel Discussions - Q & A

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Two scientists working with gravimeterNovember 26, 2018

BATON ROUGE, LA – Throughout the month of October, 10 members of the National Geospatial-Intelligence Agency visited LSU’s campus and other statewide GPS sites to take gravity measurements for a research project spearheaded by LSU Center for Geoinformatics (C4G) Chief of Geodesy Cliff Mugnier.

Every five to 10 years, the NGA takes measurements of the earth’s gravity field to check for subsidence, a project Mugnier has been working on for nearly 30 years.

“LSU has the largest university-owned network of permanent GPS stations in the world, which reach from Louisiana throughout the Gulf Coast,” Mugnier said. “Over the years, I have asked the military to come in to take measurements at these stations. I first go to the New Orleans Corps of Engineers, whose colonel then writes a letter to the Pentagon asking if they can come to Louisiana and observe different places where we have our GPS antennas for our research on subsidence. The idea is if you come back to the same spot over a period of years and see an increase in the strength of the earth’s gravity, that means you’re getting closer to the center of the earth, which equates to subsiding.”

The NGA kicked off its recent Louisiana trip at LSU’s Absolute Gravity Station using instrumentation similar to the FG5-X Absolute Gravity meter that C4G purchased this year. C4G also houses two CG5 Relative Gravity meters. From LSU, the NGA team—consisting of two groups of five trainees from New Mexico, Whiteman Air Force Base in Missouri, and both the East and West Coasts—moved on to other GPS core sites across south Louisiana that included Oakdale, Alexandria, New Orleans, Slidell, Boothville, Lafayette, Lake Charles, Cocodrie, and Grand Isle. The NGA will take measurements in north Louisiana this winter to conclude their 2018 Louisiana campaign.

“The reason for these gravity measurements is to have a completely independent physical measurement of vertical movement as a function of gravity, rather than readings from the GPS satellites,” Mugnier said. “It all fits together for the subsidence research, but another reason is when people mortgage their homes, the banks require them to have flood insurance, which is based on elevation. The Corps [of Engineers] is also interested in subsidence because they have the responsibility of levees and flood control.” 

The NGA hasn’t visited Louisiana since 2003, shortly after Mugnier arrived at LSU. Though subsidence is of vast importance to Louisianans, the NGA does not take measurements every year because subsidence is a slow process.

“If you do it too frequently, the observations get lost in what is called white noise,” Mugnier said. “Even though the instruments are super precise, you still have to have the time for the sinking to be enough for the instruments to detect.” 

Mugnier’s research on Louisiana subsidence began when he taught at the University of New Orleans, where the first NGA measurements were taken in 1989. Since then, research has shown that UNO’s campus is sinking at a rate of 9.1 mm/year, which Mugnier said is significant when you consider that equates to 3 feet in 100 years.

“Three feet is a whole lot when you also consider sea level is rising about 2 mm each year,” he said. 

Since the first reading taken at LSU around 2003 by the National Geodetic Survey, it has been discovered that LSU’s campus is subsiding around 5 mm/year near the fault line on Nicholson Drive. The campus is on the downside of the fault.

Since subsidence is an unstoppable force, Mugnier has made sure that C4G will continue his research when he is no longer at LSU. The man who started C4G, LSU Professor Roy K. Dokka, established the organization whose mission is in keeping with state law that says C4G is the source to keep track of elevations for the state of Louisiana.

“So, we have an organization that’s going to be here long after I’m gone,” Mugnier said. “And we have the perfect research project that will go on forever.”

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Contact: Erin Verpil
Center for GeoInformatics
Coordinator
225-578-8743

Welcome to the LSU Center for GeoInformatics (C4G)
Home of the Louisiana Spatial Reference Center (LSRC) and the 
GULFNet Continuously Operating Reference Station (CORS) Network
http://LSRC.lsu.edu

Access to the LSU/C4G/LSRC Free GULFNet CORS data
=================
Data can be retrieved via anonymous ftp from CORS.lsu.edu on port: 8021
or by pointing your browser to ftp://cors.lsu.edu:8021/ GULFNet CORS stations are owned and operated by C4G. The data collected by all GULFNet CORS is distributed to the public free of charge. All LSRC CORS GNSS data files collected from GULFNet CORS stations are made available to NGS & the public in Trimble’s proprietary data-file formats (R00/T00/T01/T02) or (.DAT or .TGD). All GULFNet CORS files found in this data archive are logged in formats by native to Trimble GPS/GNSS receivers from "Record Type 27" (RT27) files. The data include observation, meteorological, navigation/ephemeris for the stations. Most data are available within 1 hour from when they were recorded at each remote CORS site.
Louisiana NGS CORS
======================== NGS redistributes some of the GULFNet CORS data to the public free of charge through its partnership with the LSRC at LSU's Center for GeoInformatics. NGS publishes it's subset of the GULFNet CORS data through their CORS website found at the following links. https://geodesy.noaa.gov/CORS/ http://alt.ngs.noaa.gov/CORS NOAA's National Geodetic Survey (NGS) operates the Continuously Operating Reference Station (CORS) network that consists of group of Global Navigation Satellite System (GNSS) reference stations which provide code range and carrier phase data to users in support of postprocessing applications. The stations are owned and operated by federal, state, local agencies, private companies, and university groups, and NGS redistributes their data to the public free of charge. The GNSS data collected at these stations are made available to the public by NGS in Receiver INdependent EXchange (RINEX) format. The data include observation, meteorological, navigation/ephemeris, station logs and NGS coordinate files for the stations. Most data are available within 1 hour from when they were recorded at the remote site, and a few sites have a delay of 24 hours. ACCESS TO DATA ================= Data can be retrieved via anonymous ftp from geodesy.noaa.gov or alt.ngs.noaa.gov or ftp://geodesy.noaa.gov/cors or ftp://alt.ngs.noaa.gov/cors Alternatively a customized data request service is available at: http://geodesy.noaa.gov/UFCORS FILE RETENTION POLICY ====================== RINEX observation, meteorological, navigation and TEQC summary files: Hourly files are only kept for 2 days Daily files are kept permanently However after 30 days the 24hr (daily) RINEX observation files that are gzipped ({ssss}{ddd}0.{yy}o.gz) are decimated to a 30 second sampling rate equivalent to the {ssss}{ddd}0.{yy}d.Z site specific GPS navigation files are only kept for sites that NGS submits to the IGS network Meteorological files are available only for sites with independent meteorological sensors After six-months to one year the second copy of the RINEX observation files that are gzipped is removed i.e. file name {ssss}{ddd}0.{yy}o.gz All orbit files are kept permanently Coord files are updated as needed Logs files are updated as needed Plot files are updated daily NGS CONTACT INFORMATION ================================== If you have questions about this file or about CORS in general please check http://www.ngs.noaa.gov/CORS/ http://alt.ngs.noaa.gov/CORS or email ngs.cors @ noaa.gov

 

Louisiana State University’s Center for GeoInformatics (C4G) in its role as the Louisiana Spatial Reference Center (LSRC) has been awarded a grant for $3.1 million over the next five years (2018-2023) from the National Oceanic and Atmospheric Administration (NOAA) for their support in the Regional Geospatial Modeling. The Principal Investigator and Project Director is Boyd Professor George Z. Voyiadjis, Director of the C4G with Co-Investigators Randy L. Osborne, Clifford J. Mugnier and J. Anthony Cavell. Larry Dunaway and Jon Cliburn round out the investigating team.

$400K Micro-g LaCoste FG5-X Absolute Gravity Meter
Setup of C4G’s new $400K Micro-g LaCoste FG5-X Absolute Gravity Meter on the Baton Rouge – AA gravity mark in the CEE Materials Lab located in Patrick F. Taylor Hall.

The LSRC’s grant awarded in collaboration with a continuing 5-year Gulf Coast-wide partnership among Mississippi, Texas, Louisiana, Florida and Alabama; is to support the improvement and modernization of NOAA’s National Spatial Reference System (NSRS). Key to these efforts will be the collection of accurate, precise, and consistent geospatial data to improve regional geospatial models and to coordinate the use of this geospatial data by users to improve the NSRS for the states bordering the northern Gulf of Mexico. Partnership outreach efforts will bring awareness, access, and education to users of the NSRS. The geospatial data resources produced through the partnerships will improve NSRS Height Modernization efforts across the entire northern Gulf of Mexico coast.

The LSRC at Louisiana State University proposed a unified, regional partnership that will focus on the following objectives as the Louisiana portion of the broader proposal package submitted by the University of Southern Mississippi.

C4G staff participated in the 2018 NACAG at Table Mountain
C4G staff Jon Cliburn & Larry Dunaway participated in the 2018 North American Comparison of Absolute Gravimeters event heald at NOAA’s Table Mountain Gravity Observatory in Longmont, CO.

LSRC will work to enhance the infrastructure of geodetic control, coastal remote sensing data, terrestrial gravity measurements and other physical datasets. Various means will be used which include deploying two Scintrex CG-5 Relative Gravity Meters that were purchased at a cost of $100K each under prior grants, one from a NOAA/NGS height modernization grant and another from an LSU Board of Regents grant. C4G’s new self-funded $400K Micro-g LaCoste FG5-X Absolute Gravity Meter will be deployed to collect terrestrial gravity measurements at the C4G’s Continuously Operating Reference Stations (CORS), NSRS benchmarks, and LSRC eccentric benchmarks, which will allow LSRC to improve the geodetic modeling for future datums and NSRS modernization.

Several newly acquired pieces of equipment will be used for these observations. The Scintrex Trident Tripod, which in conjunction with C4G’s CG-5 Relative Gravity Meters will be used to observe the Gravity Gradient by accurately positioning the gravity meter at three predetermined levels for quick and precise measurements. The LSRC will acquire through the NOAA grant a $100K Digital Zenith camera in the first year of this grant from the Institute of Geodesy and Geoinformatics located at the University of Latvia and use this new instrument to measure the vertical deflection at CORS sites. The deflection of the vertical is a measure of how far the gravity direction has shifted, caused by local anomalies, which helps increase the accuracy of local surveys of the Earth’s gravity field.

Typical InSAR image taken of the Greater New Orleans area.
Typical InSAR image taken of the Greater New Orleans area.

LSRC will also collaborate with NASA’s Jet Propulsion Lab (JPL) in order to investigate targeting methods using InSAR to track regional subsidence to help develop guidelines and tools to access geodetic control and to manipulate and analyze geodetic data.

LSRC continues to maintain its existing geospatial data clearinghouse it established to provide free access to information that includes CORS raw data, flood maps, satellite, and aerial photography, digital elevation models (e.g., LiDAR, RADAR, and InSAR), and other relevant assets necessary for regional geospatial modeling.

The national goal is to develop models with accuracies better than 2 cm (3/4 in.). The dynamic nature of Louisiana’s geology makes it an outlier when continental geodetic models are developed, with many negative results for Louisiana. The LSU C4G has demonstrated the ability to observe precise terrestrial gravity, elevations and geometric relationships to the degree necessary for improving the geodetic models. Observing and possibly predicting subsidence in south Louisiana and along the Gulf Coast has been an acute challenge recognized since the 1950s, and becomes more acute with time. The NOAA grant seeks to build on the work of the LSU C4G that shows promise of bringing Louisiana, and the Gulf Coast into the norm, permitting accurate geoid models, flood mapping, coastal studies, levee construction and public safety in general.

NGS plot shows GEOID12a produces 95% confidence at ± 4 to 8 cm in Louisiana
NGS plot shows GEOID12a produces 95% confidence at ± 4 to 8 cm in Louisiana

The Center for GeoInformatics was created in 2001 to build new research and services in Geodesy and Geoinformatics for the geodetic and geophysical communities. The C4G, in cooperation with NOAA’s National Geodetic Survey (NGS), founded the Louisiana Spatial Reference Center in 2002 as a partnership focused on a state-of-the-art positional infrastructure for the state of Louisiana and to provide technical leadership, training and access to positional data. LSRC is responsible for the network of GNSS control stations; a reliable spatial reference system in Louisiana (GULFnet). The C4G maintains the GNSS Real Time Network (C4Gnet), established in 2007 to serve surveying, mapping, utilities, emergency response, agriculture, forestry, public safety, transportation, machine control for construction, environmental, and scientific research. – Positioning Louisiana for the Future.

    The Center for GeoInformatics (C4G) in the Department of Civil and Environmental Engineering (CEE) recently received new geodetic instruments to model the Earth’s gravity field. A Scintrex CG-5 Relative Gravity Meter, Leica T60 Total Station, and Trimble R10 GPS Rover Kit were acquired as part of an enhancement grant sponsored by the Louisiana Board of Regents. Drs. George Voyiadjis (PI) and Joshua Kent (Co-PI) led the one-year project, which ended in June, 2017. The instruments are acquired to address the needs of three objectives: First, to develop a novel, high-resolution gravity model of sea level (i.e., geoid); second, to augment knowledge of existing subsidence rates and the driving mechanisms; and finally, promote advanced geodetic research at the University.

Here, as in many river deltas around the world, land surfaces are sinking due to subsidence. On average, southern Louisiana experiences ~10 millimeters per year of subsidence.   Understanding the mechanisms that drive subsidence is essential for mitigating risk and promoting sustainability.  The CG-5 relative gravity meter supports these goals by measuring the relative differences in the Earth’s gravity across southern Louisiana.  Surveys using the total station and R10 rover kit are currently underway to geodetically correlate the CG-5 data with absolute gravity readings collected in the early 2000s by the National Geospatial-Intelligence Agency and the National Geodetic Survey. The updated gravimetric surveys conducted by C4G researchers and staff will deliver much needed insight into the variety of geophysical processes driving the spatially and temporally heterogeneous rates of subsidence measured across the state. 

In addition to the subsidence research, this enhancement grant will directly and indirectly benefit Louisiana’s geodetic stakeholder and consumer communities. For nearly a decade, the C4G has provided tools, services, and other geodetic resources dedicated to precise positioning throughout the state and across the region.  Central to these resources is the C4GNet real-time reference network.  The network includes more than 50 continuously operating GPS reference stations (CORS) installed across Louisiana.  Over the next five years, the C4G plans to geodetically correlate the gravity measurements with antenna heights at each station.   Extended surveys will include CORS in neighboring states.  When completed, the data will contribute to the creation of a novel, high-resolution geoid model that will allow the geodetic community to accurately and precisely measure elevations above sea level.

The instruments acquired by this grant represent an investment into the geodetic research capacity at the C4G and CEE.   In addition to the above goals and objectives, these resources have already been selected for use by investigators in two external funding proposals, both of which will rely on the precision of these instruments to deliver meaningful geodetic solutions.  These instruments not only promote research activities, they have galvanized national and international collaborations with partners across the US Gulf Coast and western Europe.  More information about these instruments and geodetic models is available at the C4G website www.c4g.lsu.edu or gravity.c4g.lsu.edu.