[OZAPRS] Know GPS? Try this quiz...

[Dave Horsfall]

Nicked from the GPS/GNSS newsletter, 6 Nov 2002
(http://www.navtechgps.com/Newsletters/GPSetc_News_November_6_2002.asp).

--
Dave Horsfall  DTM  VK2KFU  dave at esi.com.au  Ph: +61 2 9906-3377 Fx:
9906-3468
(Unix Guru) Pacific ESI, Unit 22, 8 Campbell St, Artarmon, NSW 2065,
Australia

---------- Forwarded message ----------

4) GPS QUIZ #3

GPS Quiz - Part I Volume 3
(The principal author of the questionnaire is Dr. Jayanta Kumar Ray
(email:
jkray at 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

Grade your performance:

Excellent (13-15), Very good (11-12), Good (8-10)

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)

References:

1. Kaplan, E.D. (1996), "Understanding GPS Principles and Applications,"
Artech House Publishers, Boston.
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.
4. Misra, P. and Enge, P. (2001), "Global Positioning System: Signals,
Measurements and Performance," Ganga-Jamuna Press, Lincoln, Massachusetts.
5. "NMEA (2000)," National Marine Electronics Association, NMEA 0183,
Version 3.00.
6. Parkinson, B.W. and Spilker, J. J. Jr. (1996), "Global Positioning
System: Theory and Applications," Volume I, American Institute of
Aeronautics and Astronautics, Inc, Washington D.C.



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