LORAN can be jammed.

See UK and France:

* https://insidegnss.com/uk-and-france-renew-ties-resilient-pn...

I feel like gps nav software should start considering the jamming and spoofing cases as real conditions they will encounter that should throw up an INOP warning.

It wouldn't take much smarts for it to consider the type of vessel it's in and the max and current speeds. If the calculated position of a 10 knot vessel suddenly jumps 100 km away in seconds, that sure seems like a spoof. And if you had 10 satellites locked and then you have none, that sure seems like jamming, or you're in a tunnel; INOP either way.

VOR is extremely short range and requires an extraordinary number of transmitters to provide any volume of coverage. Additionally it cannot provide coverage over oceanic areas. We USED TO have a nearly global long-range land based navigation system called LORAN, which only required one master station and a few remote stations to provide continent-scale coverage. But it was decommissioned in a cost savings move after it was determined that it could be replaced by GPS. It worked perfectly fine until it was decommissioned in 2010, not that long ago.

In the '90s I used to fly light aircraft back and forth between Seattle and Alaska. You were frequently out of range of any VOR transmitters, but that LORAN always worked. NDBs? That didn't work so great for Ron Brown.

https://en.wikipedia.org/wiki/Loran-C

And LORAN. But it may make a come-back.

GPS signals are just incredibly weak so it takes next to nothing to drown them out, easier still if you are above the receiver.

Also see https://q-ctrl.com/ironstone-opal

I'm sorry, but a multi-kilogram (at a guess), five-figure-priced (at a conservative guess) device with kilometer-scale error (per their actual press release) is not a substitute for a GPS.

And you probably can't improve on many of those specs no matter how much "inventing" you do. There's just not that much information in magnetic fields, especially if you don't spend an infeasible amount of money on keeping maps up to date. You're probably jammable, too.

The same applies to the gravitational hacks, and the mapping issue applies even to visual navigation.

Those guesses, by the way, are because not only is AQNav's "data sheet" worthless fluff, but they seem to be allergic to letting anybody even see a picture of the product. Which makes me doubt that they actually have what a normal person would think of as a "product" to begin with.