Next message: Lu Abel: "Re: GPS shortcomings."
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
> >>>
> >>>
> >>>
> >
> >
> >
> >
