PL-TR-91-2087 AD-A2 3 i 736 MILLIMETER-ACCURACY SATELLITE NAVIGATION C. C. Counselman Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge, MA 02139 8 April 1991 EL E CT,_ Scientific Report No. 9 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED. 91-04310 PHILLIPS LABORATORY III III 111111 II !II1 AIR FORCE SYSTEMS COMMAND HANSCOM AIR FORCE BASE, MASSACHUSETTS 01731-5000 b 009
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MILLIMETER-ACCURACY SATELLITE NAVIGATION C. C. … · FIELD GROUP SUE-GROUP INAVSTAR Global Positioniric- :iystem, CP,1s elit 08 05 ~~navigation, satellite geoc;esy, spac-Geusy ai
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PL-TR-91-2087 AD-A23i 736
MILLIMETER-ACCURACY SATELLITE NAVIGATION
C. C. Counselman
Massachusetts Institute of Technology77 Massachusetts AvenueCambridge, MA 02139
8 April 1991 E L E CT,_
Scientific Report No. 9
APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED.
91-04310
PHILLIPS LABORATORY III III 111111 II !II1AIR FORCE SYSTEMS COMMANDHANSCOM AIR FORCE BASE, MASSACHUSETTS 01731-5000
b 009
This technical report has been reviewed and is approved for publication
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6a NAME OF PERFORMING ORGANIZATION 6b. OFFICE SYMBOL 7a NAME OF MONITORING ORGANIZATIONMassachusetts Institute (It aplc-ble)PhlisLbrtyof :echnnology Room 37-552PilpsLbrty
6c. ADDRESS (City. State, and ZIP Code) I7b. ADDRESS (City. State. and ZIP Code)
77 Massachusetts Avenue Hanscomn Air Force Blase, MA 01'131 5000Car-,r i (i ;,, MA 02139
8a NAME OF FUNDING / SPONSORING 8b. OFFICE SYMBOL 9. PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER,WIGAMZATlON (it applicable)
Philli.ps Laboratory jGL/','WG F1962,q-86 ',or'0o
8c. ADDRESS (City, State, and ZIP Code) 10. SOURCE OF FUNDING NUMBERS
Haso irFreBse A073 00 PROGRAM PROJECT TASK WORK UNITsanco Ar ore ase M 073-5CCELEMENT NO. NO. NO, ACCESSION NO,
___________________________________ 61102F 2309 G1 I BN_
11 TITLE (Include Secvnty Classification)
MAillimeter-Accuracy Satellite Navigation
12, PERSONAL AUTHOR(S)C. C. Counselman
13a TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPOR~T (Year, Month, Day) 115. P AGE COUNTScientific No. 9 FROM 86Apr-29 TO 9lAprO8 91 Apr 08 24
16. SUPPLEMENTARY NOTATIONCopies of 22 transparencies projected during oral presentation at C. S. Draper Laboratory.Th-ese provide an outline of the talk. A complete transcript does not exist.
17 COSATI CODES I18.SU BJECT TERMS tCon~nue on reve rse if necessary and identfy by block number)
FIELD GROUP SUE-GROUP INAVSTAR Global Positioniric- :iystem, CP,1s elit08 05 ~~navigation, satellite geoc;esy, spac-Geusy ai
I positioning, radio interferometry19 ABSTRACT (Continue on reverse if necessary and Identify by blork number)
Milli:meter- accuracy satellite. nav-igation', defined as the deorni-nat ion of instantaneouspos~tion coordinates of a point on a moving platform (land/sea/air/space vehicle) withrespect to a reference frame defined by points f xod o-n t-hp ~rud with m-llinieter -level uncertainties, is pc~ssi lile using tho ia.e.i Ld-1c :lteifteromei~iy techniquesdeveloped under Contract, Fl%628-86-K-no09 and its pr~-~so. These tec:hriques:nc-ude use of doub].y-dif ferenccd, dual- Land, 1ocrsr1-ed- arie -pae observationsof the NAVSTAR -,PS sa-1ell,2 " tacm->-zoith uknown' point arJ fr-m £ixetAreferece points sui-tably arrayed on, the ground so thrit the intp'rjer-cycie amigui tiesof their observations car. he resolved to reduce satellite. -irit uncertainties. Fo r
r.';,tantIanpouF; ambi gu ity Vresol ut ion of the moving -plat I r r obs-er vat ions, at l east sevenSaI-PllltOes Must be obhserve1d simultan-eously. If the- iva-,lable number of NAVSTARsat~l ites is nsuff,,r-iort_ GLONA.SS satellites may bhos~ Other Opt ions for
ar-b~'i'.- rsoluticin are al s rivailable.
20 DISTRIBUTION / AVAILABILITY OF ABSTRACT 21 ABSTRACT SECURITY CLASSIFICATIONni UNCLASSIFIED/UNI-IMITED (j] SAME AS RPT EDTIC USERS tJNCLASSIFIED
22a NA MP OF r t ; 22b. TELEP H-ONE (Include Area Code 21C OF I E S M ODi . Thor-i:; P. Ro-nrey (617) 3'7 348o F PL/1.W-Gj
DD FORM 1473, 84 MAR 83 APR editon may be used until exhausted SECURITY CLASSIFICATION OF THIS PAGEAll othier echtions are obsolete
1INCLASO IFD
MILLIMETER-ACCURACY
SATELLITE NAVIGATION
Definition:
Determining instantaneous position
coordinates of a point on a moving
platform (land / sea / air / space
vehicle) with respect to a reference
frame defined by points fixed on the
ground, with 1-mm uncertainties.
"Satellite navigation" means navi-
gation using satellites. (The moving
platform may also be a satellite.)
MILLIMETER-ACCURACY
SATELLITE NAVIGATION
Object of this talk:
To convince you that mm-level
navigation is possible.
Plan:
1. Show you how positions of fixed
points have been determined with
millimeter accuracy.
2. Show you how positions of moving
points have been determined with
centimeter accuracy under certain
conditions.
3. Discuss prob-"s and solu..l...
2
Re: HOW POSITIONS OF FIXEDPOINTS HAVE BEEN DETERMINED
observations of same satellite at tworeceiving points cancels sensitivity to
satellite-transmitter phase.
Difference between simultaneous ob-
servations of any two satellites at anyreceiving point cancels sensitivity toreceiver-related phase.
6
Double-Differencing (continued):
In general, sensitivity to any "common-
mode" effect, including any
" receiver-related (satellite-independent)
effect, or any" satellite-related (receiver-independent)
effect,cancels when observations are doubly-
differenced.
The only surviving effects are those
which are "doubly different,"
i.e., different for observations of different
satellites, differently at different
receivers.
7
Surviving Effects, Bad & Good:
Chief of the baddies (error sources) istropospheric refractivity. E.g. at one ofthe receiving points but not the other,one of the sate'lites but not the otherappears behind a cloud. A problem ifobserving from under the weather.
The desired sensitivity of the observa-tions (to the unknown position) is not atall reduced by differencing between thisposition and another, and is not muchreduced by differencing between satel-lites if these satellites are well separatedin the sky.
8
I FIXEDeridin~ W~tic REFRENGapogdoches
4? W K M 1POINTEk
- .-
REFERPENCE ' ~' ONSWo UNKNOWN
POSITIONS
Austinn
T .s
,-ms
9
Scatter of RepeatedDeterminations on
Three Days (spanninga week) of the NineUnknown Positions
10
t5 * Pt. #2
North , . i I(MM) IM , i = 6, . ... -'-10 -5 5 6 10
i- 5 -
-10
East (mm)R.m.s. in ea. coord. -2 mm.
10
FIXED-POSITIONING DEMONSTRATION
COMMENTS:
1. All antennas/receivers* removed and
replaced each time.
2. All receivers were codeless (immune
to GPS "A-S" and "S-A").
3. Nothing but crystal oscillators.
4. No observations except from the 12
points shown (3 ref. + 9 unk. pts.)**
5. Daytime, solar maximum (high and
rapidly varying ionospheric refraction).
6. Gulf coast weather (humid, lots of clouds)
* except at two of the reference points, at Austin and Nacogdoches.**Three other stations were used, on one day, to determine
coordinates of reference points.
11
WHY IT'S FUNDAMENTALLY HARDERTO DETERMINE POSITION ON AMOVING PLATFORM (AS OPPOSEDTO A FIXED POINT):
Errors can't be time-averaged. (The
worst error source, doubly-different
tropospheric refraction, varies over
minutes to hours.)
WHY IT MAY (OR MAY NOT) BE HARDER
IN PRACTICE:
Resolving the integer-cycle ambiguities
of the doubly-differenced phase obser-
vations is harder if you can't wait for the
satellites to move to different positions
in the sky.
12
AMBIGUITY RESOLUTION
The interpretation of a (doubly-differenced)
phase observation in terms of position is
ambiguous. The "likelihood" function of
position, given a set of phase-difference
observations A4, of one or more satellites,
differenced between the unknown position r
and some reference position, is
L(r) = 21E e2 (ik- -r 's jk/X)
over all over allobserv'n satellites, ktimes, j
( Sk = unit-vector in direction of kth satellite at jh observationtime;
X = carrier wavelength; sum may include observations at multiple
wavelengths.)
13
AMBIGUITY EXAMPLE:
Suppose that there is just one observationtime (e.g. because we want instantaneousposition on a moving platform) and that twosatellites, in directions s, and , areobserved at this time. Then the position-
likelihood is maximized by
-r 0 (Sl -$2) = X (A 1 - Ak 2 + n)
where n is any integer. The maximum-likelihood position estimate is the locus of
points on an infinite set of parallel planes,
perpendicular to (s -S2) and separatedalong this direction by NIJsl-s 21.
14
ANOTHER EXAMPLE:
Six satellites observed at Li wavelength only,
for 15 min. (each satellite moves -1/8th rad.).
LIKELIHOOD FUNCTION (in E-W plane):
EAST WESTlm 8 I m
I. i 3- 1
uPI" . .
... . .. 1..
w.
%B
. ... ...
t Percent of Max.
... ..
q -l-e
.... 8S- 95
S....
:: .. ::::DO:.-
*'1 a 69-55
15
SAME EXAMPLE, except obs'ns continue fortwo hours (each satellite moves -~ 1 rad.).
LIKELIHOOD FUNCTION (in E-W plane):EAST WEST
up
Percent of Mlax.
9S-186
78- 85
DOWN ....r --
Fig. 2. Like Fig. 1, except the period of observation is 2 h instead ofIS min.
16
ANOTHER EXAMPLE (provided by G. L.
Mader of NGS, Rockville):
e 7 satellites
e Li & L2 wavelengths
* 1 point in time
* moving platform (P-3 airplane nr. Pax R.)
LIKELIHOOD FUNCTION (3-D, perspective
view):P-3 PaxRiue' 12/12/89 1 1 l. LlALZ 1 pt 11:34:38 b 1781Z. aizk
.9
17
.6.
.
17
FOR INSTANTANEOUS AMBIGUITY
RESOLUTION:
* observe both Li & L2
° account for ionosphere (unless very near
reference point)
* observe at least 7 satellites
OPTIONS:
" resolve ambiguity once and maintain track
" combine GLONASS & GPS
" use other satellites (MARISAT;
GEOBEACON)
18
19
GL-TR-89-0231
Feasibility of Millimeter-Accuracy GeodeticPositioning and Vehicle TrackingWith Repeater Satellites
Laureano Alberto Cangahuala
Massachusetts Institute of Technology77 Massachusetts AvenueCambridge, MA 02139
27 July 1989
Scientific Report No. 5
APPROVED FOR PUBUC RELEASE; DISTRIBUTION UNLIMITED
GEOPHYSICS LABORATORYAIR FORCE SYSTEMS COMMANDUNITED STATES AIR FORCEHANSCOM AIR FORCE BASE, MASSACHUSETIS 01731-500
20
United States Patent [19] [ii] Patent Number: 4,912,475Counselman, III [451 Date of Patent: Mar. 27, 1990
[54] TECHNIQUES FOR DETERMINING with Low Component Sensitivity for Use in the VideoORBITAL DATA Range of Frequencies", Proceedings of the IEEE. vol
[75] Inventor: CharlesC. Counselman. U. Belmont. 59 (1971), pp. 1617-1618
Mass. C. C. Counselman. III and I. I. Shapiro. "MiniatureInterferometer Terrmnals for Earth Surveying," Pro-
[73] Assignee: Massachusetts Institute of ceedings of the Second International Symposium on Satel-Technology, Cambridge, Mass. lite Doppier Positioning, vol. 11, pp. 1237-1286, Jan
[21] Appl. No.: 330,976 1979. Available from the University of Texas at Austin.
[221 Filed: Mar. 29, 1989 (List continued on next page.)
Related U.S. Application Data Prmary Examiner-Thomas H. TarczaAssistant Examiner-Gregory C. Issing
[63] Continuaion of Ser. No 28.712. Mai. 20. 1987. aban- Attorney. Agent. or Firm-Morgan & Finnegandoned
[51] It. CI.4 ........................ HO4B 7/185; GOIS 5/02; [57] ABSTRACT
GOIC 21/00 Techniques are disclosed for determinung orbital data of[52] U.S. CL ................................. 342/352; 342/424; space borne vehicles including earth satellites such as
364/459 those of the NAVSTAR Global Positioning System.[58] Field of Search ............... 342/352. 356, 357. 358, Each of a set of such satellites transmits signals which
342/424:364/459 include carrier waves which may be suppressed. or only(561 References Cited implicity present. The signals are received from the
observable satellites concurrently by means of an an-U.S. PATENT DOCUMENTS tenna at each of at least three ground stations forming a
4.387.376 6/1983 Sherrill et al ..................... 342/424 network of baselines. The stations are arrayed such that4.b,47,.942 3/1987 Counselman. III ................ 343/797 the ratio of the maximum to the minimum baseline4.667.203 5/1987 Coun.elma. III ...... ........... 342/357 length is much greater than one. From the signals re-4.809,005 2/1989 Counselm III ................ 342y352 ceived at a station pair forming each baseline a time
series of doubly-differenced phase measurement data isFOREIGN PATENT DOCUMENTS formed which is biased by an integer number of cycles
2120489 2/1986 United Kingdom . of phase. The data sernes for different satellite and sta-tion pairs are processed together to determine the orbits
OTHER PUBLICATIONS of the satellites and the doubly-differenced phase biasesKing et &I., Surveying wtth GPS. Monograph, No. 9, Utaque iiesermnaoon of the integer "'aiues of at leastSchool of Surveying. Uruv. of New South Wales. 1985. some of the biases is facilitated by the above notedBossier et At., Using the Global Positioning System for spatial arrangement of the stations such that the ratio ofGeodetic Positioning, pp. 553-563, Bull. Geod. 54 the maximum to the minimum baseline length is much(1980). greater than one. This integer bias determination en-W N. Christensen and 1. A. Hogbom, Chap. 7. Entitled hances the accuracy of the related orbit determination."Aperture Synthesis". pp. 171-189, of Book Entitled"Radiotelescopes", Published in 1969 by the Cambridge Unque determination of the integer values of at leastUniversity Press. England. some of the doubly-differenced carrier phase biases mayA. E. E. Rogers. "Very Long Baseline Interferometry also be facilitated by the use of a plurality of camerwith Large Effective Bandwidth for Phase Delay Mea- frequencies with the ratio of the maximum to the mini-surements", Radio Science, vol. 5, No. 10. pp. mum frequency being much greater than one.1239-1247, Oct.. 1970.A. E. E. Rogers, "Broad-Band Passive 90' RC Hybrid 18 Claims. 6 Drawing Sheets