eLoran and GPS

[Bullshooter]

I am posting to ask a question about a book I have read. I will attach a page that describes the eLoran system and suggests that since GPS can be compromised by bad actors, sunspots, and possible other factors, a hybrid Loran/GPS system has been sought by the U.S. Government to have a fallback in case GPS fails.

The book, Navigation Through the Ages, was published in 2009, so 15 years ago. I have not heard anything about such a hybrid system. For all I know it is currently in use and commercially available. As a matter of curiosity, can anyone comment on whether there has been further development, or discarding of this idea?

The attachment does a better job of describing this issue than I did.

BSer

[requiem]

So far as I'm aware there hasn't been much progress made. By the time there is progress, we'll likely all have ring laser gyros in our cell phones along with neutrino detectors.

[Jammer]

The eLoran discussions have gone next to nowhere. Most of the money and concern around GPS alternatives is for time synchronization uses, not navigation. Many people are unaware that some telecommunications and power distribution systems depend upon accurate (on the order of milliseconds) time synchronization between locations.


There is no Loran-like wide-area alternative to GPS under serious consideration at this point, but there are some metropolitan-scale experimental projects using the 900 MHz band out there.

[AA3JY]

“The U.S. Government has long been aware of GPS’s shortcomings, and in recent years various government branches have pushed for a re-appraisal of eLORAN.

As early as 2008, during the end of the Bush Administration, a press release was issued reporting the development of eLORAN as a supplemental navaid. Unfortunately, the recession hit, and nothing materialized until LORAN-C, and LORAN in general, were decommissioned in 2009.

However, discussions of eLORAN didn’t cease, and it was only a few years later when President Obama switched back to support LORAN, signing the Coast Guard Authorization Act of 2015 near the end of his presidency. The Act advocated for working with public and private entities to develop, “a positioning, navigation and timing system to provide redundant capability in the event Global Positioning System signals are disrupted, which may consist of an enhanced LORAN system.”

More recently, President Trump signed the National Timing Resilience and Security Act of 2018, which called on the Department of Transportation to reduce our critical dependency on GPS, propose an implementation plan to make America less dependent on GPS within the next two years and discuss creating possible eLORAN facilities.

Sadly, as of now, there’s still no news as to the development or completion of this plan.”

[barnakiel]

As long as we have the Sun and the sextant (and the chronometer ...) then do we truly need any alt to gps ??


b.

[Jammer]

If you're going to enter the harbor in the fog, then you either need GPS or the radiobeacons that have all been decommissioned.


Celestial Navigation is a wonderful thing offshore. For coastal navigation it lacks precision and availability as you can only get a fix at certain times of the day and under certain weather conditions.

[Bullshooter]

Interesting stuff.

I thought you guys would know something about it!

Thank you

Bser

[requiem]

Originally Posted by Jammer

If you're going to enter the harbor in the fog, then you either need GPS or the radiobeacons that have all been decommissioned.

Personally I'd prefer radar over those other two.

[GordMay]

I never make predictions.
I never have, and I never will.

An "enhanced Loran” service, eLoran, is one of several positioning, navigation, and timing [PNT] systems proposed, as a backup for GPS.
In the USA, Hellen Systems, UrsaNav, and Serco are working on eLoran projects, under DOT contracts.
For the eLoran system to cover the contiguous United States, six towers are needed, for timing applications, and 19 are needed, for position and navigation.

Because the ‘timing resilience act’ mandates that eLoran would have to be built by a public-private partnership, development would not have to wait, on the federal government’s annual funding cycles.
The question is: Who wants to pay for it?
That is where things got stuck. PNT is used by everybody; so, there is no agency, within the U.S. government, that is responsible for PNT.

Currently, Loran-C transmitters are deployed in England, France, Germany, Norway, and Denmark, together with differential eLoran reference stations, that provide better than 10-meter positioning accuracy, at seven ports, and port approaches along the English, and Scottish, east coast.
Russia and China also operate Loran-C and eLoran stations.
South Korea, which has been the victim of jamming, from North Korea, is deploying an eLoran test bed.
India and Saudi Arabia also operate Loran-C systems, and are pursuing upgrading them to eLoran.

China is using eLoran timing signals, to increase the security, and reliability, of financial, communications, and other infrastructure.
This paper [1] introduces the eLoran timing system principle, the characteristics of the eLoran and GNSS systems, and the current development status, of eLoran, in China. According to the paper, the system is planned for completion in 2026.

[1] “Analysis of the Development Status of eLoran Time Service System in China” ~ by Chaozhong Yang et al
➥ https://www.mdpi.com/2076-3417/13/23/12703

[s/v Jedi]

I don’t understand you

We have become much less dependent on GPS since we now have two additional global positioning systems: GLONAS and Galileo. Modern GNSS receivers have 72 channels supporting all three simultaneously!

About celestial vs coastal navigation: when you approach the coast from offshore you can simply use radar for precise navigation. Why does everybody forget about radar all the time? You can do bearings, distance, everything

[requiem]

Originally Posted by s/v Jedi

We have become much less dependent on GPS since we now have two additional global positioning systems: GLONAS and Galileo. Modern GNSS receivers have 72 channels supporting all three simultaneously!

Very much agree on the radar aspect, but I'm not sure about that dependence bit. I'd argue the addition of multiple constellations is primarily risk reduction from a national security standpoint, but doesn't address other risks.

Those risks being:

• Failure of onboard receiver (addressed by redundant hardware)
• Failure due to jamming or space weather (likely to impact all constellations)
• Failure (intentional or not) in a single system (this could get messy...)

Regarding that last item, if you have one system providing erroneous data, do you know how your receivers handle it? Does your HDOP simply jump from 3m to 3000m or will the receiver have some way to toss the bad data? Does the receiver attempt to determine which is the outlier, or does it simply fall back to a "trusted" constellation?

[Jammer]

Radar is my favorite piece of electronics on the whole boat.


I don't think it's sufficient for staying in the deep part of the channel in really poor viz. My radar does poorly in cluttered harbor areas and especially rivers and canals. There are too many nearby returns and so it can't see things that would be useful as landmarks.

[grantmc]

Originally Posted by barnakiel

As long as we have the Sun and the sextant (and the chronometer ...) then do we truly need any alt to gps ??
b.

Oh and nautical almanac and/or tables too. Yes?

Nightly disappearing Sun, bad weather covering sky.
GPS is very easy and convenient comparatively, to pinpoint where I am.
(RADAR is also incredibly useful for coastal navigation.)

[PippaB]

Funny how things come together. I remembered reading this thread a few days ago, and then see news of NexNav's filing (full document set) and comments to take over most of the 902-928MHz band and privatize it for PNT.

The EFF has a counterpoint.