As Loran Fades, Attention Shifts to DGPS and SBAS
Sam Wormley
http://www.gpsworld.com/survey/as-loran-fades-attention-shifts-dgps-and-sbas-9181?print=1
December 2, 2009
By: Eric Gakstatter
Few precise-positioning users have employed Loran in a professional sense, although maybe
you have in your personal life if you’re a airplane pilot or a mariner. Then again, if
you've flown as an airline passenger or cruised onboard a ship, you've benefited from the
back-up to GPS that Loran provides. Similarly, if you've used a mobile phone recently; you
don't see it, but the wireless carriers all use Loran as a back-up. That back-up is about
to go away.
Loran was developed initially for marine navigation and then adopted for aviation
navigation. I used Loran-C for aviation navigation in the early 90’s after I earned my
private pilot’s license. It was much easier than triangulating off of VORs and NDBs. Yes,
GPS receivers for aviation were starting to emerge at that time but flying is expensive so
a hand-held GPS was an out-of-reach luxury for a newlywed who just bought his first house
and was preparing to start a family.
Loran is a terrestrial (ground-based) system of broadcasting towers, somewhat synonymous
with NDGPS. You can read details about the system in the link I provided, but essentially
it’s a line-of-sight system in which the Loran receiver antenna needs a direct path to the
tower to utilize the signal. Coverage depends on the density of the broadcasting towers.
Some regions are covered better than others and when I was using it, there were many areas
that were not covered. Accuracy is always an ambiguous subject with respect to navigation
technologies, so I’ll go out on a limb and say that Loran-C accuracy is repeatable to
about 20 meters. A proposal was floated to upgrade Loran to a system called e-Loran which
is reportedly accurate to about 9 meters.
Anyway, over the past several years there’s been a discussion about what to do with the
Loran system because it’s clear that GPS has supplanted Loran as the primary navigation
system for marine and aviation. Several articles have been published in GPS World by
industry experts with most being in favor of maintaining Loran. The primary argument is
that we need a back-up system for GPS, not only for navigation, but for the many invisible
ways that GPS supports the national infrastructure (financial networks, wireless
communications, transportation).
HIPAR
> As Loran Fades, Attention Shifts to DGPS and SBAS
'Loran is a terrestrial (ground-based) system of broadcasting towers,
somewhat synonymous
with NDGPS. You can read details about the system in the link I
provided, but essentially
it’s a line-of-sight system in which the Loran receiver antenna needs
a direct path to the
tower to utilize the signal. Coverage depends on the density of the
broadcasting towers.'
???
--- CHAS
frijoli
>
> 'Loran is a terrestrial (ground-based) system of broadcasting towers,
> somewhat synonymous
> with NDGPS. You can read details about the system in the link I
> provided, but essentially
> a direct path to the
> tower to utilize the signal. Coverage depends on the density of the
> broadcasting towers.'
>
> ???
>
> --- CHAS
HIPAR
> HIPAR wrote:
>
> > 'Loran is a terrestrial (ground-based) system of broadcasting towers,
> > somewhat synonymous
> > with NDGPS. You can read details about the system in the link I
> > provided, but essentially
> > a direct path to the
> > tower to utilize the signal. Coverage depends on the density of the
> > broadcasting towers.'
>
> > ???
>
> > --- CHAS
>
> What was your question?
I'm questioning the veracity of the the segment of the article I
quoted. Let's start:
a) 'Loran is a terrestrial (ground-based) system of broadcasting
towers' -- True
b) 'somewhat synonymous with NDGPS' -- Not even close LORAN is a
hyperbolic radio navigation system
c) 'but essentially it’s a line-of-sight system in which the Loran
receiver antenna needs a direct path to the
tower to utilize the signal' -- LORAN is not a line of sight
system. It's signal operates at 100 kHz and propagates by ground wave
and ducting modes. There is often a sky-wave signal component.
d) 'Coverage depends on the density of the broadcasting towers.' --
Not really; more like the location of a (relatively) small number of
towers.
--- CHAS
Wolfgang S. Rupprecht
> Several articles have been published in GPS World by industry experts
> with most being in favor of maintaining Loran. The primary argument is
> that we need a back-up system for GPS, not only for navigation, but
> for the many invisible ways that GPS supports the national
> infrastructure (financial networks, wireless communications,
> transportation).
It is not like Loran is going to provide the microsecond clock
synchronization that cell towers need.
The government seems to be really bad at closing down anything, no
matter now antiquated and expensive it is to run. I was just reading
about how the post office was losing billions per year but they can't
lay off unneeded labor and they can't close underutilized post office
locations. It would cost political brownie points. It is easier to just
keep underutilized services going forever.
-wolfgang
--
Wolfgang S. Rupprecht
If the airwaves belong to the public why does the public only get 3
non-overlapping WIFI channels?
utilsea
I was LORAN C user long time ago (not so long, I'm not so old :-)
As far as I know, this year USA and perhaps GB decided to modernize
actual LORAN C network covering north atlantic
See on this forum some post relative to this or here
http://www.insidegnss.com/node/551#Baseband_Technologies_Inc_
Why spending money in a system without a world coverage and an
accuracy of few hundred metres ?
Just have a look on the frequency used (100khz) know that this
frequency can be received under few meters under water and look for
who need the best discretion at sea and for wich this accuracy is more
than enought.
You will see who is the main user of this system...
Utilsea
Alan Browne
> As Loran Fades, Attention Shifts to DGPS and SBAS
> http://www.gpsworld.com/survey/as-loran-fades-attention-shifts-dgps-and-sbas-9181?print=1
>
> December 2, 2009
> By: Eric Gakstatter
>
> Few precise-positioning users have employed Loran in a professional
> sense, although maybe you have in your personal life if you’re a
> airplane pilot or a mariner. Then again, if you've flown as an airline
> passenger or cruised onboard a ship, you've benefited from the back-up
> to GPS that Loran provides. Similarly, if you've used a mobile phone
> recently; you don't see it, but the wireless carriers all use Loran as a
> back-up. That back-up is about to go away.
I don't know of any airliner that has used Loran of any flavour. A lot
of military, some survey and other special missions aircraft have.
I'm not sure to what degree Loran permeates today as you describe.
Again, airliners did not use it; certainly not in any significant number
and the few airplanes I saw it on were usually special missions of some
kind or other. (I did rent a -172 with one once and played with it a
bit on a x-country flight).
For continental operations VOR/DME formed (still does) the navigation
reference for en route nav (with a smattering of NDB's). For oceanic
routes, INS and Omega/VLF were the nav systems of choice for airliners.
Accuracy requirements were not very tight over the ocean... I'd bet
that about 1/2 of airliners today still rely more on INS for oceanic
flights than GPS.
I'd say the "right" way to go is to help the Europeans get Galileo up
and commissioned asap. Then you will see commercial receivers that use
both signals concurrently in the solution ( PR is PR as far as the math
is concerned) and of course can run on either source of signals alone.
Roy Lewallen
an installed base of receivers. So to make it viable it'll be necessary
to convince GPS users to install a presently unnecessary Loran receiver
and antenna for the day that GPS might fail. While this might not be a
bad idea for critical military users, it'll be a hard sell for the
civilian market. Demand will be small so prices will be high. Without an
installed base of receivers, Loran won't be viable as a backup -- it
would take a long time -- I'd guess years -- after GPS system failure
for receiver manufacturers to gear up to meet the demand, for equipment
to be installed and checked, users trained, and procedures developed to
use it.
Are all you folks promoting Loran going to buy a portable Loran receiver
to keep in your car's glove box? Install one in your Cessna? Petition
the FAA to develop Loran instrument approaches?
Roy Lewallen
frijoli
I didn't see anyone here promoting it.
Since it's already in place it doesn't need promoting,
however that doesn't necessarily mean it should continue to
be supported, nor does it mean it should be discontinued.
Clay