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 ±1cm 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:

Benjamin Fernandez has built this tool optimized for Louisiana that you can use by simply putting in a place, address or zipcode to search for what Benchmarks are needed in any area your interested in.  

            

C4G Call to Action for Louisiana Survey Community to collect GPS on BenchMarks!

Vertical controls for all surveys shall be determined in the North American Vertical Datum of 1988 (NAVD88). All measurements shall be referenced to local control stations of the National Spatial Reference System, specifically the public domain Louisiana State University Continuously Operating Reference Stations network or other currently National Oceanographic and Atmospheric Administration National Geodetic Survey approved reference stations, such as benchmarks, monuments, or continually operating reference stations.

https://legis.la.gov/Legis/Law.aspx?d=410843

C4Gnet.XYZ GNSS Online Post Processing - powered by Trimble Online Processing App

Works throughout Louisiana and some parts of Mississippi and Texas.

Get a Free C4Gnet.XYZ GNSS Online Post Processing Service Account, user accounts are available for the C4Gnet.XYZ GNSS Online Post Processing Service which requires a yearly free subscription that is available simply by asking one of the C4Gnet.XYZ administrators. To get a free user account, first Register Here then send an email to This email address is being protected from spambots. You need JavaScript enabled to view it. or This email address is being protected from spambots. You need JavaScript enabled to view it. and request a free C4Gnet.XYZ GNSS Online Post Processing Service Subscription.

Here is a list of other free online GPS post-processing services:

  • OPUS: (Currently Under Government Shutdown) NGS GPS Data Processing Online Positioning User Service
  • CSRS-PPP: Canadian Spatial Reference System, Natural Resources Canada
  • AUSPOS: Geoscience Australia
  • GAPS: University of New Brunswick
  • APPS: Jet Propulsion Laboratory
  • SCOUT: Scripps Orbit and Permanent Array Center (SOPAC). University of California, San Diego
  • magicGNSS: GMV
  • CenterPoint RTX: Trimble Navigation

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