GPS NAVIGATION
AND
THE BACKUP
ISSUE
by
Langhorne Bond
Delivered to:
“THE FUTURE OF GPS:COMMERCIAL
OPPORTUNITIES”
A CONFERENCE
SPONSORED BY
WHITE HOUSE WEEKLY
WITH BACKUP BY
GPS WORLD
From
the earliest days of GPS, technical experts have commented on, and warned
about, the vulnerability of the GPS signal.And
for good reason:the signal comes
from low powered satellites 11,000 miles above the earth.The
signal received on or above the earth is below the level of background
electronic noise.One commentator,
trying to describe the signal in layman’s terms, compared it to the light
received from a 25-watt bulb 11,000 miles away.
Modern
receivers work nicely with such a tiny signal.Most
of the claims made for this marvelous navigation and location system are
proving out.
Marvelous
as it is, however, the GPS system has one serious weakness:it
is so low powered it can easily be blotted out or disrupted.
Within
the past year there has been a cascade of well publicized incidents.
Here
are some highlights:
·At
the Moscow Air Show a primitive, first generation jammer
operating on 4 GPS frequencies at only 5 watts of power was able to destroy
the GPS signal for a distance of 200 kilometers.Retail
price:$3,500.Unspecified
“middle eastern” customers had acquired the jammer.
·
Numerous US Department of Defense exercises blotted out GPS at various
regions all over the
·
The President’s Commission on Critical Infrastructure Protection (PCCIP),
a top level White House technical advisory group, described GPS navigation
as the greatest single risk to
·
Very recently a shadowy group of international computer hackers, known
as Masters of Downloading, announced they had cracked the US DOD code that
controls the GPS satellites.Now these
folks, wherever they are, may be able to send up a signal that turns off
the GPS birds.Or sets them spinning
uselessly, like Galaxy 4.
·
Two high level
II.GPS
AND NAVWAR
GPS
was, and is, first of all a military system.The
US DOD has publicly directed that all military weapons systems – aircraft,
cruise missiles, and precision guided munitions such as standoff missiles
– be equipped with GPS guidance.DOD,
of course, has always been aware of the vulnerability of the GPS signal,
and has been conducting an extensive counter-jamming program to minimize
GPS signal loss, and to restore the signal.These
efforts have been black; and properly so.I
expect the work to go on forever:it’s
the fog of war.
One
outcome of this work is that the DOD has decided to include inertial systems
in its planes and rockets. AKA, a backup system.
Mike
Shaw of the DOD’s satellite office was recently quoted as saying, “There
is very little we can do to prevent intentional jamming.”
Is
there a lesson here for civil users?
III.GPS
– A LIMITED EDITION MIRACLE
Those
of us who have harped on the vulnerabilities of GPS have been subject to
a lot of griping from the GPS advocates, and the criticism is really not
fair.Everyone realizes that GPS is
a breakthrough, and it will be universally used for radiolocation and radionavigation
all over the globe.It will be especially
useful where there is no location signal at all – at little or no cost.
Useful
though GPS is, however, it is not perfect.Vulnerability
is its greatest limitation.This limitation
affects different users differently.
IV.WHO
IS AT RISK?
It
is now estimated that only 10% of the $10 + billion annual market for GPS
products are for aviation and marine navigation. The bulk of this market
– agriculture, railroad train tracking, truck and container management,
surveying, backpacking, etc. – are in applications where the loss of the
GPS signal is an annoyance, and is expensive.But
life is not at stake.
Aviation
and marine navigation are different.Plane
loads of people and vessels full of thousands of passengers and explosive
and toxic cargo depend for safety on radionavigation
signals.
Consider
a typical night when the entire East Coast of the
The
risk to vessels is similar.The latest
mega cruise ships will have four thousands souls on board. Loss
of the GPS signal will put them into danger and onto submerged rocks with
great loss of life.
V.SOLE
MEANS NAVIGATION
Originally
it was thought that GPS, because of its universal coverage and great accuracy,
would be all that was needed for every phase of flight.Now
we know better.The notion of GPS
as the “sole means” of navigation for aircraft and vessels is dead.The
passing was officially announced to the world by the
VI.GPS
NAVIGATION LIVES!
GPS
navigation is alive and well.It
just needs a little help.
The
serious debate amongst navigation and safety experts now is about the most
effective, lowest cost mix of systems that will meet the public’s need
for assured safety.
The
outcome of this debate is very important to the manufacturers and users
of navigation systems.The first company
to figure it out and put the right equipment on the market, the first company
fully to embrace the new reality, will get out ahead of the pack.
The
question of the hour is – GPS plus what?
VII.THE
GREAT BACK-UP DEBATE
FAA
system architects and planners are trying to define the appropriate navigation
service needed for the various areas of the world, classes of users, and
kinds of air traffic.Here is an
outline of the issues.
A.Enroute
Flight Over the Oceans, the Poles, and Unequipped
Land Masses
Today
these parts of the globe are overflown by
heavy, well-equipped aircraft—airliners and biz jets—going from one well
equipped airport to another.There
are no ground based radio signals available here and virtually all aircraft
use modern inertial systems with a very high level of accuracy.These
triple redundant systems are self-contained and therefore immune to jamming
or outside interference. GPS may have benefits here.The
ideal is an integrated GPS/inertial nav
system which protects against loss of GPS.
B.The
Outback/Forward Areas/the Interior
Undeveloped
areas of the world such as the Canadian north, Alaska, central Australia,
much of Africa, central Asia, the interior of Brazil, to name a few, have
little density of air traffic and no ground based radio navigation at all.GPS
in these undeveloped areas is a real breakthrough, providing accurate navigation,
and a vertically guided precision approach to a high decision height, to
the small aircraft typical in these regions.In
these areas where no terrestrial radionavigation
signal at all is available, GPS is an obvious safety improvement.Here,
a back-up system is not yet in place, so loss of GPS is just a return to
the status quo ante.
C.The
Developed World
The
developed world—Europe, North America, Japan, and the populated conurbations
of the rest of the world, are now equipped with totally reliable ground
based navaids whose accuracy and continuity
meet world standards of safety.
In
these areas traffic is heavy, the routes are tightly spaced, and the loss
of all navigation and approach signals would be catastrophic.
The
standard navaids in developed areas are
VOR/DME, NDB, LORAN C, and ILS.In
these areas a back-up system for all phases of flight—en route, terminal
maneuvering, and precision approach—is mandatory.
VIII.PROTECTION
AGAINST LOSS
A.RAIM
RAIM—receiver
autonomous integrity monitoring—is a mnemonic for a GPS receiver feature
which tells the pilot or ship captain immediately when the GPS signal is
lost or unusable.This feature is
the first line of defense against
GPS
unreliability and should be mandatory for all GPS navigation receivers,
both airborne and maritime.
FAA
and the Coast Guard should require RAIM for all GPS receivers, even when
teamed with dissimilar systems such as VOR/DME, ILS, and LORAN C.
B.VOR/DME
The
VOR/DME system includes 1027 transmitters in the
C.ILS
There
are 1,100 ILS’s in the
FAA
plans to scrap all 1,100 ILS in the near future.At
least that’s the plan.
The
GPS signal would supplant ILS within a decade.The
GPS signal, when augmented by WAAS and LAAS, can provide an accuracy to
CAT I or better precision approach standards.The
problem is that the GPS signal often disappears, sometimes because of the
inherent causes, often from intentional interference.
ILS
is the only back-up for GPS for precision approach, and it is now universally
acknowledged that a complement of ILS’s
will remain in service for the foreseeable future.So
the commercial opportunity for every IFR equipped aircraft lies with an
integrated ILS/GPS precision approach receiver.This
will permit a descent-stabilized precision approach wherever a GPS signal
can be received plus an ILS approach when needed.
So
the question is, how many ILS’s (and VOR/DME’s)
should be retained as a back-up?
D.The
Skeleton System
FAA’s
answer is the skeleton system, a name only FAA could have come up with.Within
the agency there is now a draft plan to retain a skeleton system of VOR/DME’s
and ILS’s.Approximately
80% of both networks would be scrapped.The
remaining 250 or so of each would be available for those days when the
sun, or terrorists, or the DOD blot out the GPS signal.
The
skeleton system has been carefully coordinated with the satellite enthusiasts
in the Air Transport Association’s staff.You
will not be surprised to learn that only the major airports keep ILS’s
and VOR/DME’s.The
little airports and the smaller hubs are stripped bare.At
least 500 of the 630 airports with ILS’s
are to be denuded.In my opinion,
this ATA-sanctioned scheme is a severe threat to air carrier safety.
The
general aviation situation is even worse.FAA
proposes to scrap virtually all the VOR/DME’s
and ILS’s used mainly by the little guys.GA
gets no back-up at all.
Amazingly,
the AOPA has joined forces with ATA in this plan.The
carriers and the GA lobby have jointly endorsed the “sole means” doctrine
and have endorsed a skeleton back-up network that is inadequate for air
carriers and non-existent for business and small aircraft.Are
the general aviation leaders paying attention?
E.LORAN
C
The
LORAN C navigation system presents a special case because it serves both
aviation and maritime users.
Approximately
1.3 million LORAN C navigation sets are in use in the
The
use of LORAN C for marine navigation is critical.Only
the LORAN C signal follows the surface of the earth and is therefore received
by vessels at distances of 500 or more miles.LORAN
C is the only back-up signal to GPS for vessels.That’s
why the NTSB has endorsed its teaming with GPS.
The
LORAN C signal is very difficult to jam.The
high powered long wave signal covers the entire
LORAN
C costs, by government standards, virtually nothing.A
private firm has offered to operate and modernize the entire
US LORAN C chain of 26 stations for $12 million per year.
And
the US DOT proposes to close down every LORAN C station and take the navigation
signal off the air.
This
position is incomprehensible.The
FAA’s historic antipathy to LORAN C is at least understandable—the Coast
Guard runs it.But the Commandant’s silence,
and Secretary Slater’s disengagement, are harder to fathom.Did
the Vice-President’s technology-dazzled staff send down orders to kill
all but the satellite systems?That
is the rumor.
IX.THE
LIABILITY SYNDROME
On
the afternoon of the last day of the Rio Conference something very important
happened.You may have missed it,
because the entire aviation trade press missed it.The
delegates from 100 nations endorsed a multi-lateral treaty to establish
the obligations and liability of GNSS providers, namely the
Here
is the reason.The Presidential Decision
Directive (PDD) that set out US policy on GPS specifically reserved to
the President (“the National Command Authority”) the right to degrade,
spoof, or turn off the GPS signal at any time, anywhere, for any reason.And
we have refused to enter a GPS agreement to which we would be bound.Given
that our troops use the GPS signal for virtually all our delivery systems,
and that our enemies can use the signal against our troops, this is absolutely
the right policy.
But
it makes other nations more than nervous when they tie their economies
to GPS.This is why the Europeans
almost certainly will put up their own GPS look-alike satellite system.
Hence
the decision to move toward a multi-lateral treaty which will require the
provider to enter a binding commitment to keep the signal going without
interruption and which will also pin liability for failure of the system
on the provider and, probably, on the manufacturers of the satellites and
of the receivers.
The
formal approval for a liability convention must come from the ICAO Assembly
this fall and the convention itself would be a year from then.Ratification
into effect would take still longer but not, I predict, too long.What
nation will delay ratifying a treaty that pins liability for an aircraft
crash or surveying error caused by loss of the
I
doubt the
This
is a matter to which the companies pursuing the $10 billion GPS market
might want to pay attention.
May
I suggest the most promising defense against a bankrupting liability suit
in, say,
There
is only one ultra low cost, unjammable,
highly accurate back-up system with coverage right down to the ground.It’s
LORAN C.
Thank
you.