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The GPS/GNSS newsletter by Navtech Seminars
& GPS Supply,
the GPS professional's resource since 1984. |
| November 6, 2002 |
|
Editor-in-Chief:
Carolyn P. McDonald (send news items to cmcdonald@navtechgps.com)
Technical
Editor: Keith D. McDonald (satconsult@aol.com)
Production
& Design:
F'Lynne Didenko (fdidenko@navtechgps.com)
Welcome to "GPSetc.com
News" published
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news! To see previous
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Included
in this Newsletter:
(click on hyperlinks below to jump to news items)
1)
Performance Analysis of Navigation Systems Involving GPS
in
Australian Airspace by Professor Brian
O'Keeffe
2)
Navtech Seminars' 2003 Schedule Now on Web!
3)
Register for December 2002 Courses in New Orleans!
Look for Our Postcard!
4)
GPS Quiz #3
5)
NAVCEN News
6)
GPS Launch to be Rescheduled Due to Delta 2 Rocket Damage
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1)
Performance Analysis of Navigation Systems Involving GPS in
Australian Airspace by Professor Brian O'Keeffe
Brian O'Keeffe is an Adjunct Professor in Communications
Engineering at the University of Canberra and the Managing
Director of FANS PLANS P/L which provides consultancy services
nationally and internationally on the planning and
implementation of new electronic systems for civil aviation. He
has spent over 45 years in the development of new electronic
systems for civil aviation. He was the Vice-Chairman and then
Chairman of the ICAO Future Air Navigation Systems (FANS)
Committee which developed the new Communication, Navigation,
Surveillance and Air Traffic Management system which has now
come into operation in many areas.
When he retired from Airservices Australia in 1997, he was
the Special Technical Adviser to the Chief Executive. He has
received numerous national and international awards for his
contributions to aviation. In particular, he was awarded
Aviation Week's Aerospace Laureate in Electronics and received
the Capt. PVH Weems Award from the Institute of Navigation.
Professor O'Keeffe has shared with us the results of his
research reviewing the performance of currently used and
proposed navigation systems utilizing GPS for general aviation
IFR operations in Australian airspace. The abstract is included
here, but to see the report in its entirety, please see the PDF
at the following link: http://www.navtechgps.com/Newsletters/Nav_Sys_Performance.pdf.
ABSTRACT:
Since the introduction of satellite navigation using GPS for
civil aviation commenced in the early 1990's, many developments
in the satellite constellation and receivers have taken place.
It has therefore been timely to review the performance and
operation of the currently used and proposed navigation systems
involving GPS for GA operations in Australian airspace. This
analytical study concluded that aircraft using receivers
complying with TSO C146 (with Fault Detection and Exclusion and
ranging from geostationary satellites) would be provided with
superior navigation performance than available from current
operations with ground based navigation aids such as NDB.
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2)
Navtech Seminars' 2003 Schedule Now on Web!
Allocate your training budget now! Click HERE
to see our 2003 schedule of courses.
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3)
Register for December 2002 Courses in New Orleans!
Look for Our
Postcard!
If you have requested to be on our Navtech Seminars' mailing
list, keep an eye out for our postcard - you should receive it any
day now!
...and be sure to book your hotel room by November 16!
The courses to be presented in New Orleans December 9-13,
2002 are:
(click the titles to see course outlines)
To browse our course outlines and for specific information
about course locations, our 2002 and 2003 schedules, or to register
on-line, click HERE.
To subscribe
to our mailing list to receive our paper catalog of courses,
click HERE.
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4) GPS Quiz
#3
GPS Quiz - Part I Volume 3
(The principal author of the questionnaire is Dr. Jayanta
Kumar Ray (email: jkray@accord-soft.com)
of Accord Software & Systems Private Limited, Bangalore,
India. Accord Software and Systems is a leader in programmable
DSP-based GPS Receiver Technology. The references for this
questionnaire, pinpointing the page numbers where the answers
can be found, are given at www.accord-soft.com
under the heading “GPS Quiz”)
1. The relativistic effect in a GPS satellite clock which is
compensated by a deliberate
clock offset is about
a) 4.5 parts in a million
b) 4.5 parts in 100 million
c) 4.5 parts in 10 billion
d) 4.5 parts in a trillion
2. The following component of the ephemeris error contributes
the most to the range
error:
a) along-track error
b) cross-track error
c) both along-track and cross-track error
d) radial error
3. The peak electron density in the ionosphere occurs in a
height range of
a) 50-100 km
b) 250-400 km
c) 500-700 km
d) 800-1000 km
4. The refractive index of the gaseous mass in the
troposphere is
a) slightly higher than unity
b) slightly lower than unity
c) unity
d) zero
5. Rank VDOP, HDOP and PDOP from best to worst (normal
conditions):
a) VDOP, HDOP, PDOP
b) VDOP, PDOP, HDOP
c) HDOP, VDOP, PDOP
d) PDOP, HDOP, VDOP
6. If DGPS corrections to the range measurements are made
using the data from a
reference station situated at about 100-200
miles, and the resulting position is found to
be significantly biased, that means
a) no ionospheric or tropospheric corrections were applied
to the
measurements at the reference
receiver and remote receiver
b) ionospheric and tropospheric corrections were applied to
the
measurements at both the reference
receiver and remote receiver
c) the observations are wrong as there should not be any bias
for whether
or not ionospheric and tropospheric
corrections are applied to the
reference and remote receivers
d) None of the above
7. The UTC time and the GPS time are offset by an integer
number of seconds (e.g., 13
seconds as of January 1, 2001), as well as a
fraction of a second. The fractional part is
about:
a) 0.1-0.5 sec
b) 1-2 ms
c) 100-200 ns
d) 10-20 ns
8. The differences between pseudorange and carrier phase
observations are
a) integer ambiguity, multipath errors and receiver noise
b) satellite clock, integer ambiguity, multipath errors
and receiver noise
c) integer ambiguity, ionospheric errors, multipath errors
and receiver
noise
d) satellite clock, integer ambiguity, ionospheric errors,
multipath errors
and receiver noise
9. If the range measurements for two simultaneously tracking
satellites in a receiver are
differenced, then the differenced measurement
will be free of
a) receiver clock error only
b) satellite clock error and orbital error only
c) ionospheric delay error and tropospheric delay error only
d) ionospheric delay error, tropospheric delay error,
satellite clock error and orbital error
only
10. Zero baseline test (code) can be performed to estimate
a) receiver noise and multipath
b) receiver noise
c) receiver noise, multipath and atmospheric delay errors
d) none of the above
11. The NMEA message $GPGLL has fields for
a) latitude-longitude position
b) speed and heading
c) satellite elevation-azimuth-signal strength
d) all of the above
12. GPS week number started incrementing from zero at
a) midnight of Jan 5-6, 1980
b) midnight of Jan 5-6, 1995
c) midnight of Dec 31-Jan 1, 1994-1995
d) midnight of Dec 31-Jan 1, 1999-2000
13. The complete set of satellite ephemeris data comes once
in every
a) 6 seconds
b) 30 seconds
c) 12.5 minutes
d) 12 seconds
14. For high accuracy of the carrier phase measurements the
most suitable carrier tracking
loop will be
a) PLL with low loop bandwidth
b) FLL with low loop bandwidth
c) PLL with high loop bandwidth
d) FLL with high loop bandwidth
15. Which of the following statements is NOT true to reduce
the receiver noise (code):
a) reduce the loop bandwidth
b) decrease the predetection integration time
c) space the early-late correlators closer
d) increase the signal strength
Answers:
1. (c) 2. (d) 3.
(b) 4. (a) 5.
(c) 6. (a) 7.
(d) 8. (c) 9.
(a) 10. (b) 11.
(a) 12. (a) 13. (b) 14.
(a) 15. (b)
Grade your performance:
Excellent (13-15), Very good (11-12), Good (8-10)
References:
1. Kaplan, E.D. (1996), Understanding GPS Principles and
Applications, Artech House Publishers, Boston. Available
through
Navtech
GPS Supply.
2. Lachapelle, G. (1997), GPS Theory and Applications,
ENGO 625, Geomatics Engineering, The University of Calgary,
Calgary, Canada.
3. ICD-GPS-200C (1993), Interface Control Document,
Navstar GPS Space Segment and Navigation User Interfaces,
Prepared by ARINC Research Corporation, California. See PDF at
NAVCEN’s
website. Paper copy available through Navtech
GPS Supply.
4. Misra, P. and Enge, P. (2001), Global Positioning
System: Signals, Measurements and Performance,
Ganga-Jamuna Press, Lincoln, Massachusetts. Distributed
exclusively by Navtech
GPS Supply.
5. NMEA (2000), National Marine Electronics
Association, NMEA 0183, Version 3.00
6. Parkinson, Brad W. and Spilker, James J. Jr. (1996), Global
Positioning System: Theory and Applications, Volume I,
American Institute of Aeronautics and Astronautics, Inc.,
Washington DC. Available through Navtech
GPS Supply.
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5)
NAVCEN News
-----Original Message-----
From: Casswell, Rebecca [ RCasswell@navcen.uscg.mil
]
Sent: Thursday, October 24, 2002 4:21 PM
To: Agenda List (E-mail)
Subject: JAPAN-US Announcement, CGSIC ISC European Meeting, DGPS
Mask Angle
Hello-
Japan - U.S. Joint Announcement
On October 16, 2002 in Tokyo, the Government of Japan and the
Government of the United States of America released a statement.
A copy of the announcement is located at: http://www.navcen.uscg.gov/cgsic/meetings/JapanUSGPSPlenaryMeeting.htm
CGSIC International Subcommittee European Meeting
The next meeting of the CGSIC International Subcommittee will
be held 5-6 December at Eurocontrol Headquarters in Brussels,
Belgium. The draft agenda and logistics information, including
hotels and how to get to Eurocontrol, will
be posted on the NAVCEN website by Monday at: http://www.navcen.uscg.gov/cgsic/meetings.
Lower Mask Angle Setting Improves DGPS Navigation Service
Availability Effective 22 October 2002, the US Coast Guard is
using a mask angle setting of five degrees at all Maritime and
Nationwide DGPS sites. This change in operating parameter will
be reflected in the next update to the Broadcast Standard for
the USCG DGPS Navigation Service, COMDTINST M16577.1 More
information can be found at: http://www.navcen.uscg.gov/news/MaskAngle.htm
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6)
GPS Launch to be Rescheduled Due to Delta 2 Rocket Damage
Due to accidental damage to a Boeing Delta 2
rocket that occurred while attaching a GPS satellite to the
booster, the GPS launch originally scheduled for November 7th
will be delayed at least a month. See the full story at: http://spaceflightnow.com/news/n0210/28gps2r8/
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US YOUR NEWS ITEMS, WITH SOURCES!
Carolyn McDonald, Editor
cmcdonald@navtechgps.com
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