Federal registry announcement (3/21/2018) shows that all remaining 38 NDGPS sites will close and cease broadcasting Realtime DGPS by 2020.?ÿ?ÿ
Alaskan's fought hard to keep the stations running during the last round of closures - all AK sites are slated for closure beginning 2020.
The NDGPS sites are our longest running CORS up here
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all remaining 38 NDGPS sites will close and cease broadcasting
The FR entry says that they'll stop broadcasting, but it stops short of affirmatively saying that they'll be decommissioned entirely.?ÿ Have you explored the possibility that they might be maintained as CORS?
Our CORS stations are disappearing due to attrition. They seem to have been "given" to our State Land Dept., who had no funding to operate them, and then "given" to our DOT, which has no funding to operate them either...
Jim,
I have asked my NGS advisor the same.?ÿ The terms closure and discontinued were used in this FR - similar in 2016.?ÿ Our experience from 2016 has shown any time a NDGPS station serving as a CORS that was slated for decommissioning AND went down for mechanical/power/data serving issues, the site was torn down.
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Joel
From an NGS Advisor: When the USCG discontinues a DGPS signal it also decommissions the station, so it would be removed from CORS network unless the site is adopted by another agency.?ÿ
This does mean that other agencies or entities could consider adopting these stations as they begin to blink out, and that would be an agency-by-agency decision process. In many circumstances adoption of these stations has been determined to be inadvisable due to the legal and permitting barriers associated with taking over a former DOD-operated site; when this is considered in combination with the existing stability of the DGPS mounts, equipment age (most are GPS-only receivers), and existing alternative siting options, there are typically more feasible options for sustaining a cGNSS presence at many of the former DGPS sites.
I can't speak to other areas of the country, but down here ENG5 and ENG6 are pretty unreliable and have been supplanted by other stations in the area (MARY, INRI, SBCH) that are newer and better maintained. As the article states, the Coast Guard "beacon" signals were hugely important at one time because Selective Availability made autonomous GPS unreliable and WAAS, GLONASS, Galileo, etc. did not exist. A lot of people down here did a lot of surveying in the marsh and on the water using beacon receivers; one of the great things about them was that the corrections were broadcast in NAD83 so no transformation was necessary. However, they were also broadcasting RTCM type 9 corrections, which, due to the nature of the message structure, can have a lot of latency, especially if there are more than six satellites being tracked and corrected. WAAS is a much better DGPS signal as long as you can pick up the satellite.
The long and the short of it is that the beacon stations have outlived their usefulness when it comes to their stated and intended purpose, which was to aid in coastal and riverine navigation. Hopefully at least some of the stations that are important national CORS to the people in the region will be maintained as such; as for us, if ENG5 and ENG6 go away it won't affect us much.
As Lee said, the beacon stations have essentially outlived their usefulness and been replaced by other options.
These were once essential for night navigation as well, but communication (radio) and navigation (radar) technology made them obsolete less than 20 years after they were installed.
http://www.dreamsmithphotos.com/arrow/arrows.html
https://en.wikipedia.org/wiki/Transcontinental_Airway_System
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Up here in Alaska, the loss of these stations will be pulling down valuable CORS when projected PBO site de-construction is about to begin (2018). ?ÿ I think they are still worth fighting for on several fronts.
PBO which makes up the bulk of our adopted CORS network are, like NDPGS sites, GPS-only.?ÿ Our receivers were switched out in 2014.?ÿ Our NDGPS sites have consistently better power with requirements for realtime signals at high probabilities where remote PBO sites are at a higher risk of outages due to batteries and remoteness.?ÿ The CORS stations that I have personally visited (KEN6/GUS6) are built with little to no multipath, and unlike alot of other stations, are not attached to buildings with a bolt.?ÿ ?ÿMaybe ours were built to different standards up here - i don't know.?ÿ ?ÿ
NDGPS works very well under canopy too - we tested the quality up here in Alaska with a baseline of 100km.?ÿ https://www.gps.gov/cgsic/meetings/2008/rasher2.pdf?ÿ .?ÿ But using NDGPS on land is just an added benefit from its navigational capacity on the water.?ÿ I'm not an RF guy, but those NDGPS signals are very strong, and hug the water, designed to penetrate in fjords and not for aircraft with the benefit of flying 5000' AGL.
Granted, manufacturers have all but abandoned NDGPS, but mariners are a stubborn lot who look for redundancy in the wheelhouse and in the north, on the water NDGPS supplies that extra navigational signal immune to southern horizon blockage like those encountered in SE Alaska fjords. (see comments in 2013?ÿand 2015?ÿcaptains of our ferry system).?ÿ We also could think about how susceptible we are to putting our satellite eggs in one basket (Easter reference) - PRN 135 - that supplies our highest horizon signal.?ÿ In 2010 for many months WAAS was rendered useless in our northern climes, but luckily, the satellite was not lost.?ÿ ?ÿNo matter what signal enhancements WAAS will bring to the plate, NW Alaska will remain susceptible to WAAS augmentation
NDGPS coverage and accuracy tests were conducted by USCG for many of the stations, and supported approaches to harbors.?ÿ The signal strength is undeniably strong, consistent, FREE!?ÿ with no subscription, and for us GIS guys, already in NAD83 (2010) or if you are in Hawaii?ÿ on the extreme edge of WAAS GRS coverage NAD83 (PA11). https://www.navcen.uscg.gov/?pageName=ndgpsOAReports
Up here, in the high latitudes, with predicted increase in marine traffic especially thru some very tight sea lanes, I don't think we should be pulling down maritime CORS - we should be fighting to keep them.
Gavin,
No answers here either, but 168 comments in 2015, 16% of them from Alaska, did show support for continuation of service including our ferry, pilot associations.?ÿ There is no comment period on this current NOTICE in the FR - this is a notice of closure.?ÿ All 38 active NDGPS sites will cease broadcasting and be dismantled.?ÿ Maritime use of these signals in tight spaces is where NDGPS excels and while its clear agriculture is a clear consumer, fishing and maritime traffic is going to be a clear loser up here.?ÿ?ÿ
Comparisons of WAAS and NDGPS signals in the fjords of SouthEast Alaska would be an interesting study to see. Its made clear from the NDGPS study that the broadcast is heard in areas where some of the trickiest navigation is found.?ÿ Having experienced at least 6 trips up and down through those channels during my fishing days it was vital to time a transit at slack tide (or risk going backwards in a place like Seymour narrows).?ÿ Its value for prudent navigation should be made clear.?ÿ Were talking increased cruise ships and maritime shortcuts like through Shelikof Straits that worry me most and a reliance on a Geostationary satellite built for aircraft navigation down to a few hundred feet for augmentation on the seas.
Another case that makes Alaska a little bit different and something that warrants closer inspection for us.?ÿ I don't have answers in this budget crisis were undergoing up here either, but this is where the federal level push is warranted in my opinion.
