C4G CORS Keep Rolling On

CORS AntennaOne of the most ironic effects of the political squabbling in Washington is how it illustrates our voluntary dependence on hand holding by the federal government in this the supposed “land of the free.” Besides the thousands of those on the dole (individual or corporate) bemoaning the apparent cut off of funds, there is a general shutting down of all the government websites that provide useful information; among them those of the National Geodetic Survey (NGS). NGS, incidentally, descends from the oldest government scientific agency.

NGS operates a service at its website that thousands have come to depend on called OPUS, an acronym for Online Positioning User Service. Surveyors, in the form of mappers and geodesists as well as scientific researchers or simply the curious can submit high-grade GPS (GNSS) data, fill in a few blanks and in a short while, Voila! a precise result of the position of that data is returned by e-mail. The function is possible because of a nation-wide collection of Continuously Operating GPS/GNSS Reference Stations (CORS). Very high-end antennas and receivers precisely positioned that collect and store data continuously. The owners of these CORS share this data with NGS for archiving, processing and research.

The availability of this data from NGS as well as the OPUS function has been shut down recently like all the other useful government sites, unlike those few inexplicably blessed to stay on-line. Rumors have spread within the surveying community that CORS data and OPUS-like services are unavailable. This isn’t true. Many of those who operate the CORS and provide the data to the government also make it available. This story is the reason for this blog entry. One example is the Center for Geoinformatics (C4G) at Louisiana State University. The C4G network is close to my heart since I had a hand in its establishment and the installation of most of the stations within it.

Read more in the words of C4G and on the C4G website: News LINK and Website LINK.

C4Gnet Remains Online During Government Shutdown

As you can see by the status map below C4G CORS are all online and working as expected. C4Gnet subscribers have not and will not be affected by the current Federal Government shutdown.


More information on C4Gnet and the services offered by the C4G can be found at the C4Gnet Real time Network portal site at http://c4gnet.lsu.edu/ or on the C4G website at http://c4g.lsu.edu/.


24/7 CORS Data Availability

Due to the Federal Government shutdown, NOAA.gov and most associated web sites are unavailable. However C4G and the services it provides remain online and because the C4G is the original source for nearly all CORS data here in Louisiana and we know how much the positioning community relies on this data, C4G has set up an anonymous FTP server with access to raw GNSS data from most of the Louisiana National CORS sites. This service is offered to the public free of charge by C4G and will remain in place as long as NGS is unable to make CORS data available.


The C4G anonymous FTP server is available 24/7 @ ftp://cors.lsu.edu:8021/ or in your FTP client at the following settings.

  • Host: cors.lsu.edu
  • Port: 8021
  • Login Type: Anonymous

Note: raw CORS data is used in geodesy post-processing tools like Trimble Business Center, Leica Geo Office and Topcon Tools. GIS data collected autonomously can also be differentially corrected against raw CORS data in software tools like Trimble Pathfinder Office.


Contact your GNSS dealer if you need help setting up a connection to the C4G CORS FTP server or need details on the tools necessary to post-process GNSS data.


OPUS is Shutdown, 7 Comparable Online Post-Processing Service Are Still Available

For those of you who rely on OPUS for GPS post-processing, there are seven other free online post-processing services available that produce positions comparable to OPUS.
Here is a list of the seven free online GPS post-processing services:

  • 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

Click This Link to read a great article written by Eric Gakstatter of GPSWorld.com with a report on how all of these free online GPS post-processing services compare, including OPUS.