Slashdot Mirror
US Coast Guard Intends To Kill LORAN-C
adaviel writes "LORAN (Long Range Aids to Navigation) is an electronic navigation system using low-frequency radio, used by many boaters (including me) before GPS. It has an approximately 200m accuracy and is a functional replacement in case GPS fails or the US implements selective availability in time of war. The US Coast Guard, part of the Department of Homeland Security, intends to turn it off starting February 8." This is in spite of $160M spent on modernizing LORAN stations over the past 10 years.
Comment removed based on user account deletion
"This is especially idiotic considering GPS satellites that are currently in orbit are beginning to fail, and no country wants the responsibility of modernizing them, or repairing them."
Okay...
1. The DOD depends on GPS and matains the network. So what are you talking about countries wanting to take responsibility for the GPS network? The US DOD does.
2. You do not repair or modernize GPS satellites... You replace them.
3. GPS is going to keep working until it is replaced with something else or the US stops being a nation.
"Further, what if a GPS receiver goes offline on a ship?"
You use the backup? You don't really think that a ship would only have one do you?
The reason to keep both was that many operators spent a lot of money on Loran and GPS was expensive. Now GPS is cheaper and more reliable than Loran.
Your arguments are along the lines of "We should keep paying for hitching posts on our streets so we can keep horses as a back up for cars."
See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
200m is the absolute accuracy (and is a bit pessimistic). The repeatable accuracy is much better.
That is, if you sail into a port's harbour channel and save that as a LORAN-C waypoint you will typically be able to get back to that same spot within 20m or so easily.
SA made GPS accurate to 10m.. With the "SA" feature disabled, you're down to 2m... And with Satelite enhancements, it's more like 20cm !
But that's irrelevant.. Because SA was intended to disable any enemy force from using GPS for accurate positioning - until they realized D-GPS (Differential GPS) made the whole point moot (you take a reference point - you send the signal to the receiver - And therefore - the receiver can deduce the SA introduced clock error - because now you have a ref point .. And believe it or not - it is a United Stated Uniform service - the US Coast Gard - that came up with it to overcome the artificially introduced uncertainty).
However, the military still keep exclusive use of the 1Mhz band (with the 10Mhz being public) - for the only purpose of being able to make real time measurements on tropospheric distortions - so - what happens - is that the military can make 1m accurate reading WITHOUT sat aids.
Actually, yes. When I was commercial fishing on a troller in Alaska we used Loran grid coordinates, spoken in Danish, to tell our brothers where the fish were. No one else could understand us. If we said "Over and out" the conversation was finished, but if we said "I'm off," that meant to change frequencies, tell how many King's you'd caught, and give the coordinates. Without the Loran our sneaky ways will have to be changed.
How about a moderation of -1 pedantic.
At least my recollection is that while the absolute accuracy of LORAN isn't nearly as good as GPS, it actually had better repeatability (i.e. the ability to return tomorrow to that fishing spot you found today) than at least pre-DGPS/WAAS GPS did.
Today's modern GPS systems and supplemental accuracy aids probably make this moot, but it's a major reason why LORAN has survived as long into the GPS era as it did.
G.
I've been a sailor most of my life. We haven't used Loran C seriously for almost two decades. Most boats don't even have Loran receivers any more. It's GPS all the way whether you are a casual sailor or a commercial ship captain. In fact, large commercial ships are required to use GPS and special transceivers these days (the boater's equivalent of GPS-based aircraft systems). If backup matters one could pack a RDF or maybe even a sextant, but frankly GPS has not failed even once from the day it became available to boaters. Besides, Loran C pretty much only works near the coastline of major industrialized nations (or did)... it wouldn't be all that helpful if you were lost at sea.
The coast guard should have abandoned Loran C years ago.
-Matt
There are also examples of quite amazing navigation done using sextants, particularly the voyage of the James Caird http://en.wikipedia.org/wiki/Voyage_of_the_James_Caird