Louisiana Spatial Reference Center

 

The LSU Center for GeoInformatics (C4G) continues its partnership with the USGS and FEMA to help accurately document high water marks following events like the flooding just experienced in south Louisiana. When events like this occur, the USGS receives a mission assignment from FEMA tasking them with collecting elevations of high water marks in the affected areas.

In March of this year C4G provided the vertical control needed to collect high water marks when heavy rains caused flash flooding across many areas of northern Louisiana. C4G was originally asked by USGS for help the beginning in August of 2012 following Hurricane ISAAC. The LSU Center for GeoInformatics provided USGS field crews with temporary access to its Real-Time Network (RTN), known as C4Gnet, to collect the data they need according to the FEMA Mission Assignment issued.

Once again, in the wake of the August 2016 flooding in southern Louisiana USGS has been tasked by FEMA with mission assignments to deploy numerous USGS crews in the Comite, Amite, Tangipahoa, Tickfaw, Vermillion and other basins further west to survey upwards of 600 - 800 high water marks using the C4Gnet RTN to correct all positions collected.

The USGS is a yearly subscriber to the Real-Time Network services offered by the Center for GeoInformatics but when events such as the recent flooding occur, C4G is ready and willing to step up and provide the additional temporary resources USGS needs to collect accurate data especially when public safety is at stake.

Note that the LSU Center for GeoInformatics is actively pursuing the funding necessary to do the control work needed to create better GEOID models in Louisiana. Feeding well distributed vertical control data into future GEOID models will improve the vertical accuracy of these models and is perhaps our only hope of ever creating a ±2cm GEOID in the state of Louisiana.

The NGS presentation on Friday March 15, 2013, pointed out that GEOID12a produces 95% confidence at ± 4 to 8 cm in Louisiana. The NGS conclusion states that the problem is too large for NGS to handle alone and we all need to work together to get better height results. They also recommend partnering with locals to leverage existing resources and that a plan needed to be created to move forward with improving heights.

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

The presentation was given by NGS geodesists / scientists, Michael Dennis and Dan Roman.

  • Michael Dennis was the recent project manager for the new adjustment to the North American Datum of 1983, NAD 83 (2011), and performed the S. LA project vertical adjustment.
  • Dan Roman is the head of research and development of geoid models at NGS.

Big picture ideas to consider from the presentation

  • Short term possibilities (through ~2015)
    • Extend 2009 MS leveling into and across LA
    • Establish GNSS infrastructure to monitor subsidence
    • New ~2015 GNSS Height Mod survey (gives 10-year delta time)
  • Medium term (~2016-2022)
    • Terrestrial gravity surveys
    • Incorporate GRAV-D aerial gravity into geoid model for region
  • Long term (~2022)
    • New vertical datum based on gravimetric geoid

Recently, NOAA’s National Geodetic Survey released updated orthometric heights for Southern Louisiana relative to the September 2010 GNSS Height Modernization project. These heights represent the most up to date heights available for the region. On March 15, 2013, NGS hosted a free, on-line webinar to present the results of this project.

 

Visit the NGS page for this event

To download the .mp4 file, click here.

Link to the presentation:

Bill Henning, NGSThe LSU Center for GeoInformatics hosted a training session on Best Methods to Achieve Accurate, Repeatable Orthometric Heights Using Real Time GNSS Networks. The event was held at the Orleans Parish Levee District Offices in New Orleans, Louisiana on August 15th 2012. The event was attended by over 60 individuals including surveyors, engineers, local, state and federal government officials. 

Some of the topics covered were:

  • Vertical Geodetic Control in Southern Louisiana
  • Providing the National Spatial Reference System in dynamic regions
  • Intro to GNSS
  • Guidelines for Establishing GPS-derived Ellipsoid Heights
  • Guidelines for Establishing GPS-derived
  • Orthometric Heights
  • Improvements to the Geoid Model
  • Real-time Kinematic Surveying and Best Practices
  • Introduction to Real-time Networks

The South Louisiana Flood Protection Authority District - East has made these trainings a Requirement for Professionals Working for the Levee District. Surveyors and Engineers that attended also received 8 Continuing Education Credits. The training provided professional Land Surveyors the requisite training to properly use an RTN system such as GULFNet or C4Gnet to provide current correct elevations. The main speaker was Bill Henning of NGS, one of the premier experts in the GNSS applications field. Registration, food and refreshments were handled by LSPS District 1 and plans are currently in the works to host additional events of this type in Baton Rouge and Shreveport in the near future.

If you are interested in attending one of these training events please sign up for the C4G mailing list or follow C4G in social media on Twitter, Facebook or the C4Gnet RSS feed. You can also find Podcasts, PDF's and Videos of past events on the C4G website or the C4G YouTube channel.

POSITION REPORT

GNSS Market Research and Analysis GPS/GNSS Networks and Services The Global Market for GNSS Augmentation Infrastructure and Services 2009-2013 March 2009 Abstract ©Position One Consulting Pty Ltd 2009 All rights reserved Authors Robert Lorimer & Eric Gakstatter

Global Navigation Satellite Systems (GNSS) include the United States GPS (the most commonly used today), Russia's Glonass, the EU's Galileo, China's Compass, the Indian Regional Navigation Satellite System (IRNSS) and Japan's Quasi-Zenith Satellite System (QZSS).

The signals from all these GNSS are subject to a myriad of errors and may not always tell the truth. Whereas this is not a problem for casual users or those who can tolerate such errors, there are many applications where integrity and accuracy must be improved.

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