NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: GPS shortcomings.
From: Brooke Clarke
Date: 2005 Jun 8, 18:51 -0700
From: Brooke Clarke
Date: 2005 Jun 8, 18:51 -0700
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 >>> >>> >>> > > > >
