NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: GPS shortcomings.
From: Courtney Thomas
Date: 2005 Jun 8, 23:43 -0500
From: Courtney Thomas
Date: 2005 Jun 8, 23:43 -0500
Great News ! Thank you, Courtney On Wed, 2005-06-08 at 20:51, Brooke Clarke wrote: > Hi Courtney: > > On the contrary, they will continue to work as they did, maybe better > performance because of the improvements in the antennas, transmitters > and the reference timing sources. > > But remember that LORAN-C was originally designed for coastal navigation > and now the focus is on blind aircraft landing. So the coverage area > does not extend too far from any coast. Global coverage map: > http://www.locusinc.com/images/MegapulseMap1.gif > > But I expect the coverage area to increase, especially near major airports. > > I have a number of timing LORAN-C receivers and they are almost as good > as GPS, see: http://www.pacificsites.com/~brooke/A2100F.shtml > > Have Fun, > > Brooke Clarke, N6GCE > > > > Courtney Thomas wrote: > > > Does this mean our old Loran receivers are soon worthless, or still > > usable just not as accurate, or what ? > > > > Thank you, > > Courtney > > > > > > On Wed, 2005-06-08 at 16:19, Brooke Clarke wrote: > > > >>Hi Carl: > >> > >>The current LORAN-C system is made up of chains of stations, one master > >>and a hand full of slaves. Now the slaves listen for the master pulse > >>and after a wait send their pulse. In the not too distant future all > >>stations will just transmit based on a collection of Cesium clocks. > >> > >>The result will be a more accurate fix. > >> > >>The older LORAN-C receivers could needed to be programmed for the Group > >>Repetition Interval (GRI) of the nearest chain. The new generation > >>receivers are, to borrow a GPS term, "All In View". These receivers > >>know about all the world's stations and use Digital Signal Processing > >>technology to receive all the stations at the same time. > >> > >>It was not only the events on 9/11 but also the realization that it's so > >>easy to jam GPS and European and Russian counterparts that kept LORAN-C > >>alive. > >> > >>The U.S. has turned off Selective Availability which makes a GPS fix > >>more accurate for civilian users, but to counter this the military is > >>developing jamming technology and from time to time tests it. If you > >>happen to be in a test area you position will be either wrong or non > >>existent. > >> > >>Have Fun, > >> > >>Brooke Clarke, N6GCE > >>-- > >>w/Java http://www.PRC68.com > >>w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml > >>http://www.precisionclock.com > >> > >> > >> > >>Carl Herzog wrote: > >> > >>>Lu Abel wrote: > >>> > >>> > >>>>Two or three years > >>>>ago the US Coast Guard was trying to accelerate their schedule for > >>>>shutting down Loran C. Now it looks like they and the US Department of > >>>>Transportation (which includes the US's Federal Aviation Administration) > >>>>are concerned about possible problems with GPS in navigation > >>>>applications (such as aircraft routing or precision harbor approaches) > >>>>that require hyper-reliability and appear to be considering an enhanced > >>>>Loran as a backup system. > >>> > >>> > >>>As of 1992, plans were in place to eliminate LORAN by 2015. By 1994, the > >>>termination date had been bumped up to the year 2000. Opposition by > >>>LORAN users, largely lead by general aviation interests, caused another > >>>review of the need for the system. > >>> > >>>At the same time, in an unrelated effort, the Volpe National > >>>Transportation Systems Center, a division of the U.S. Dept. of > >>>Transportation, was studying the vulnerabilities of the GPS system. They > >>>released their resulting paper on September 10, 2001. This report is > >>>available as a pdf online: > >>> > >>>http://www.navcen.uscg.gov/archive/2001/Oct/FinalReport-v4.6.pdf > >>> > >>>Needless to say, the events the next day gave the report a higher > >>>profile than it may have otherwise had. > >>> > >>>It was shortly after that the department began looking at refurbishing > >>>the existing LORAN infrastructure to backup GPS. Upgrades to the LORAN > >>>infrastructure in the U.S. are already well underway. This spring the > >>>Coast Guard upgraded all the transmitters and new timing and frequency > >>>equipment is being installed this summer. > >>> > >>>Studies are still underway to determine whether an enhanced LORAN system > >>>can completely meet standards for accuracy and other characteristics > >>>that would be required for it to serve as a backup to GPS in aviation > >>>and harbor approach navigation. So far the results look promising, but > >>>it may be a few more years before you start seeing integrated GPS/LORAN > >>>receivers for sale at your local marine supply store. > >>> > >>>Carl > >>> > >>> > >>> > > > > > > > >