Goodbye dGPS? Hello Virtual AtoNs?
No one should get overly upset quite yet, but it does seem that the U.S. Coast Guard is thinking about reducing the differential GPS (DGPS) correction stations it manages, and is also wondering if all the aids to navigation (AtoNs) it maintains are truly necessary these days. My friend Dean Travis Clark recently joined the Navigation Safety Advisory Council (NAVSAC) and he just sent around two of its working group resolutions for comments. I know he’d like to hear the opinions of Panbo readers too, and that these resolutions have not yet been finalized or presented to the USCG…
NAVSAC Resolution 12-05 is titled “Continued Maintenance / Operation of Differential Global Positioning System” and you can download it here. Remember that “DGPS” is a confusing term because it’s often also used for the satellite-based augmentation systems (SBAS) like WAAS, EGNOS, and MSAS that are used even by the tiny handheld Bad Elf Pro GPS just reviewed. The more specific DGPS that the USCG looks after in the U.S. is the earlier technology that uses ground stations and medium-frequency radio waves to deliver differential position corrections to an onboard GPS. I used to see yachts equipped with DGPS but not often these days, presumably because of SBAS and the cost of DGPS receivers like the Furuno GP150D.
Frankly, then, I don’t know much about the current state DGPS and how much it’s used by ships and the like, let alone how highly it’s valued. According to the resolution NAVSAC has tentatively concluded that the Coast Guard is underestimating DGPS use because they used the GPS accuracy flag included in AIS transmissions (only Class A can take input from a separate GPS, differential or otherwise) and also that DGPS is more reliable than SBAS. What do you all think? Should our government keep spending 15 million dollars a year maintaining the Differential stations? I must say that 15m strikes me as relatively small money…
I do have more of an opinion about NAVSAC Resolution 12-06, which is titled “Elimination or Reduction in the Number of Physical Aids to Navigation
(AtoN) and Consideration of ‘Virtual AtoN'” and can be downloaded here. I also found some valuable information about what the Coast Guard is thinking. Just go to NAVSAC’s DHS Homeport page, download the “April 2012 Summary Record and Transcripts” and scroll away. First off you’ll find that the Guard’s anticipated use of Virtual AtoNs (like the Vesper NZ example discussed here last April) will be primarily in addition to the charted physical AtoNs. For instance a VAtoN could be set up quickly to mark a dangerous wreck or a nav aid that’s dragged critically out of position. NAVSAC argues that not all vessels have the ability to display VAtoNs, which is certainly true, but don’t these examples fall into the “something being better than nothing” category?
Then contemplate the section titled “NAV 2040”, which itself is a sign of how far into the future the Guard is trying to look. That’s where I got the two slides on this page, which sum up the case for reduced AtoNs pretty nicely, I think. “Notional” is a rarely seen word meaning mental or theoretical, but I think you’ll get the idea. Navigators don’t rely on visual aids to navigation as much as they did in 1990 because they have better electronic aids onboard and ashore. I not only buy that notion, but in fact I was feeling it on my trip south. I appreciated all the markers along the narrow stretches of the ICW but truthfully I didn’t pay nearly as close attention to them as I did decades ago, because I didn’t have to. Plus I was listening to all the chatter on talk radio about how many people are dependent on government handouts while looking at an ICW that’s hardly used by commercial vessels any more. So I asked myself, “Aren’t all us snowbird cruisers welfare queens too?” Seriously, do we really need all those expensive-to-maintain beacons, buoys, and lights?
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