GPS IN AVIATION AND
THE COMING AGE OF
AUTOMATED
LANDING SYSTEMS
By Pete Hand
FRS 144 April 17th, 2006
Outline
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A Brief History of GPS used in aviation
Goals and Objectives
GPS Aviation Technology throughout the years
ILS
 MLS
 WAAS
 LAAS
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Outline Continued
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Automated Landings
In the Military
 For Commercial use
 The future of automated landing systems
 TALS
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A Brief History
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June 1991Portable/panel mount GPS that interfaces with autopilot
On February 10th, 1993, the National Aeronautic Association selected
the Global Positioning System Team as winners of the 1992 Robert J.
Collier Trophy, the most prestigious aviation award in the United
States. This team consists of researchers from the Naval Research
Laboratory, the US Air Force, the Aerospace Corporation, Rockwell
International Corporation, and IBM Federal Systems Company
February 17, 1994 The Federal Aviation Administration announces
that GPS is operational an integrated as a part of the U.S. air traffic
control system.
In 1998, Vice President Al Gore announced plans to upgrade GPS
with two new civilian signals for enhanced user accuracy and reliability,
particularly with respect to aviation safety.
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Wikipedia entry and http://www.aero.org/education/primers/gps/gpstimeline.html
History continued
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Originally only used by the military (Air Force),
but the FAA has approved its use in commercial
aviation
Commercial GPS uses a different frequency
from the Air Force uses
First commercial GPS use in 1996
GPS in Commercial Aviation
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“The objective of NAS Implementation is to
develop the operational infrastructure to support
the certification process for satellite navigation and
provide the technical basis for the development of
GPS operational procedures for all phases of flight.
NAS Implementation communicates and
cooperates with numerous governmental and nongovernmental agencies to pave the way for a
smooth transition to satellite navigation.”
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http://gps.faa.gov/programs/index.htm - National Airspace
System
Goals
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Ultimately, the FAA, NAA, NAS, etc. wish to have
GPS-based aviation systems which operate all
flights
Would create the possibility for “drone commercial
aviation” – highly unrealistic, but a rising possibility
Would make it virtually impossible or terrorists to
hijack planes – although if they ever did they could
control every plane in the sky…
Ethical problems? Economic problems? Safety
problems? All an issue…
Improvements in Landing
Technology
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Selective Availability technology – used by the gov
through 2000 – accuracy only to 100 meters
2001 – best non-SA accuracy only to 15 meters
Differential GPS – used by the Gov until late 2001 – up
to10 meters accuracy
WAAS – still used by the gov – able to attain accuracy
of up to 3 meters
LAAS – developed in 2001 – current accuracy is 16 m
laterally and 4 m vertically – but goal is go have both
accuracies down to 1 meter
Early GPS - ILS
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Instrument Landing System
 2 separate systems – one vertical guidance and one
horizontal guidance systems
 Localizer antenna located at the end of the runway –
2 signals transmitted on a carrier frequency between
108 MHz and 111.975 MHz
 Localizer receiver on the aircraft measures difference
in depth of modulation – when the difference is 0
the localizer is in line with the center line of the
runway
ILS continued
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glideslope antenna array is sited to one side of
the runway touchdown zone – follows the path
of an aircraft down the center of the runway
The GS signal is transmitted on a carrier
frequency between 328.6 MHz and 335.4 MHz
uses a technique similar to that of the localizer
ILS Diagram
ILS in Use
Localizer Antenna at Whiteman Airforce Base
MLS
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Microwave Landing System – developed by FAA NASA and the
Department of Defense
-“designed to provide precision navigation guidance for
exact alignment and descent of aircraft on approach to a
runway”
- provides azimuth (The angle of rotation (horizontal) that a
ground based parabolic antenna ), elevation and distance
- supplements ILS – has both vertical and horizontal
guidance systems
- MLS use suspended by FAA in 1994 in support of then
new WAAS technology
MLS Diagram
WAAS
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“WAAS is a GPS-based navigation and landing system that is
meant to improve safety by providing precision guidance to
aircraft for all phases of flight at thousands of airports and
landing strips where there is no ground- based landing capability.
WAAS consists of 25 ground reference stations, 2 leased
geostationary satellites, 2 master stations, and 4 uplink stations.
The ground reference stations are strategically positioned across
the United States to collect GPS satellite data. WAAS is designed
to improve the accuracy, integrity, and availability of information
coming from GPS satellites and to correct signal errors caused
by solar storms, timing, and satellite errors. Unlike conventional
ground-based navigation aids, WAAS provides curved precision
approach paths in order to avoid obstacles, restricted airspace,
noise-sensitive areas, and congested airspace.”
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http://www.gao.gov/new.items/d0511.pdf
How it Works
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25 ground stations through out the United States –
compare GPS signal with known coordinates
Report to WAAS Master Station – sends singal to
WAAS satellite
WAAS satellite sends signal back to plane
“The WAAS-enabled GPS receiver adds the correction
factor to the GPS signals to derive a corrected GPS
signal which is far more accurate than the original GPS
signal.”
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http://gps.faa.gov/Programs/WAAS/waas.htm
WAAS Diagram
History of WAAS
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Developed by the DOT and the FAA in early 1995
First precision approach technology was Instrument
Landing System – a glide path, laser guided system
Soon replaced by MLS – Microwave Landing System in
the late 80’s which used microwaves to locate the
aircraft
Soon replaced by the highly more accurate, and much
cheaper WAAS system
More History
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July 10, 2003 – WAAS signal activated for
general aviation
March 2005, FAA leases services of WAAS
geostationary satellite from Lockheed Martin
through 2016
2006 – WAAS available in 99% of the
continental United States
Problems with WAAS
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Signal often affected by cloudy weather
Signal affected by “jamming” – not so much a
problem anymore with new technologies, but
was a problem at the start of GPS landing
systems
System can only cover a limited amount of the
country due to possible receiver locations –
however this percentage has reached 99% of the
country
LAAS
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“LAAS is a precision approach and landing system
that relies on the Global Positioning System (GPS)
to broadcast highly accurate information to aircraft
on the final phases of a flight. LAAS is being
developed specifically to augment GPS satellites to
support precision approaches and landing capability
to aircraft operating within a 20- to 30-mile radius
of the airport. LAAS approaches will be designed
to avoid obstacles, restricted airspace, noisesensitive areas, or congested airspace.”
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http://www.gao.gov/new.items/d0511.pdf
History of LAAS
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Concept first in 1992
System requirements first analyzed in 2001 –
developmental stage begins
Developed in late 2001
Due to be implemented in 2006, however due to the
FAA budget the project has been deferred to 2009
Only 18 million left in the budget as of the end of 2004
– will only carry LAAS development through 2005 –
implementation will require 600 million dollars
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http://www.gao.gov/new.items/d0511.pdf
How it Works
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“The Local Area Augmentation System (LAAS)
will augment the Global Positioning System to
provide an all-weather approach, landing, and
surface navigation capability. LAAS focuses its
service on a local area (approximately a 20-30
mile radius), such as an airport, and broadcasts
its correction message via a very high frequency
(VHF) radio data link from a ground-based
transmitter.”
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http://gps.faa.gov/Library/laas-f-text.htm
LAAS Diagram
Problems with LAAS
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Only covers 20-30 miles around a single airport –
WAAS covers much more of the country and is much
more effective
VHF uplink signal currently slated to share the
frequency band from 108 MHz to 118 MHz with
existing ILS localizer – users will have to own more
than one set of radio gear to operate the system
potential for a single point of failure – caused by
weather, solar activity, or jamming – airports with
LAAS have no back up…if the system goes you’re out
of luck!
Automated Landings
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Auto-pilot can already do take-offs, and in-flight
performance – the one untested area is landings
When automated landings are perfected, unpiloted flights may become a reality.
LAAS has brought automated landings into
possibility – with 1 meter accuracy as opposed
to the 100 meter accuracy of less than 15 years
ago
Possibilities with WAAS and LAAS
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WAAS and LAAS, or a combination of the two
are bringing ever closer the idea of unmanned
flight – both in the military and civilian realms
Greatly reduces the risk of terrorism involving
planes, but also puts human lives in the hands of
robots
Not yet at the level where we can abandon pilots
New LAAS system – if it is ever implemented
would make it possible to have un-piloted flights
To Summarize
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Technology has gotten much better in the past
10 years
LAAS accuracy can not be beat, but WAAS
coverage can not be beat, thus…
Final system likely to have LAAS at major
airports with WAAS around the rest of the
country
Auto-landings history (Military)
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In 1947, The UK Blind Landing Experimental Unit (BLEU) was
established within the Royal Aircraft Establishment, now QinetiQ.
BLEU conducted the world’s first fully automatic landing in 1950 and
had significant involvement in the development programme for the
world’s first Cat IIIb landing system for civil airliners.
Later technology developed by QinetiQ's predecessor include the
Microwave Aircraft Digital Guidance Equipment (MADGE),
developed as a tactical approach and landing system and was
subsequently adopted by the Royal Navy for precision recovery of
aircraft to the INVINCIBLE class aircraft carriers.
Recent work by QinetiQ's forebears on automatic landing systems has
focussed on the use of differential and relative-GPS systems. A
number of flight trials were conducted during the 1990s to explore the
use of GPS as a means for recovery of helicopters to restricted sites,
concentrating particularly on ship operations.
QinetiQ's recent ship trial aboard HMS INVINCIBLE has
demonstrated the world’s first fully automatic STOVL shipboard
recovery and landing.
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Taken from
http://www.qinetiq.com/home/newsroom/news_releases_homepage/2005/2nd_quarter/QinetiQs_JSF_world_first.html
Automated Landing Systems – Big
News
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“September 25, 2002 -- San Diego, California. General Atomics
Aeronautical Systems, Inc., the leading manufacturer of
unmanned aircraft systems, has successfully landed its IGNAT
unmanned aircraft using a company-developed automatic landing
system. Aeronautical Systems has funded and has now fully
demonstrated the capability of automatically landing its aircraft
without the direct control of the pilot. The automatic landing
software uses differential global positioning system (GPS) which
provides an accurate cross section of where the aircraft is in
space and in relation to the ground. Using this formula, the
aircraft descends at a pre-programmed rate to a fixed point on
the ground. This company-funded effort resulted in the first
automatic landing of the IGNAT on 12 September.”
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http://www.ga.com/news.php?subaction=showfull&id=1032940800&arc
hive=&start_from=&ucat=1&he
New Landing Systems
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“the means for guiding and controlling aircraft from an
initial approach altitude to a point where safe contact is
made with the landing surface. Such systems differ
from low-approach systems in three major respects: (1)
They furnish not only guidance but control of the
aircraft as well. (2) They furnish information on the
aircraft's position with respect to the terrain below it,
and the rate at which the landing surface is being
approached. (3) They do not require the pilot to assume
manual control near the ground”
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http://www.accessscience.com/Encyclopedia/0/06/Est_063
500_frameset.html?doi
TALS
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Tactical Automated Landing System – currently the
only commercially-oriented automated landing system
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Not available for commercial use but currently in
development for commercial use
Designed by the army to reduce dangers of landing at night,
but becoming more and more commercially oriented
Could be used in planes as early as 1212 – radar landing
system dependent on LAAS technology