(12) United States Patent
`Ho?berg
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 6,252,544 B1
`Jun. 26, 2001
`
`US006252544B1
`
`(54) MOBILE COMMUNICATION DEVICE
`
`(76) Inventor: Steven M. Ho?'berg, 29 Buckout Rd.,
`West Harrison NY (Us) 10604
`
`5,285,523
`5,299,132
`5301368
`5,369,588
`
`2/1994 Takahashi ............................ .. 395/22
`3/1994 Wortham
`364/460
`4/1994 Hiram - - - - - - - -
`- - - -- 455/78
`11/1994 Hayami et al.
`364/449
`
`( 4 ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`
`5,459,667 * 10/1995 Odagaki et al. ................... .. 364/444
`,
`,
`
`
`iclllager elt a1‘ """""""" u]1ta et a . . .
`
`.
`
`’
`
`5,382,957
`
`1/1995 Blume . . . . . . . . . . . . . .
`
`. . . .. 342/43
`
`U'S'C' 154(k)) by 0 days‘
`
`(21) APP1-N°-- 09/236,184
`(22) Filed:
`Jan_25 1999
`’
`Related US Application Data
`(60) Provisional application No. 60/072,757, ?led on Jan. 27,
`1998'
`
`(51) Int. Cl. ................................................... .. H04B 7/185
`
`7
`
`U-S. Cl. ................................ ..
`342/357.13, 342/457; 701/208; 701/213
`(58) Field of Search ............................. .. 342/457, 357.06,
`342/3571, 35713, 35707; 701/207, 208,
`
`213
`
`5,523,950
`5,541,590
`5,544,225
`5,550,551
`5,563,607
`5,568,390
`5’6OO’561
`5,602,739
`5,610,821
`5 621 793
`576257668
`
`a
`
`a
`
`5,630,206
`576337872
`5,638,078
`5,646,612
`5,668,880
`
`5,673,305
`5,678,182
`
`6/1996 Peterson ............................. .. 364/436
`7/1996 Nishio ................................ .. 340/903
`8/1996 Kennedy e161.
`379/59
`8/1996 Alesio ............ ..
`342/457
`10/1996 Loomis et al.
`342/357
`10/1996 Hirota et al. .
`364/449
`2/1997 Okamura """" "
`364/460
`2/1997 Haagenstad et al. .............. .. 364/436
`3/1997 GaZis et al. ..................... .. 364/444.2
`4/1997 Bednarek et al.
`380/20
`4/1997 Loomis et a1‘
`379/58
`
`.. 455/54.1
`5/1997 Urban et al. .
`370/312
`5/1997 Dinkins
`342/450
`6/1997 Wichtel .
`7/1997 Byon .................................. .. 340/903
`9/1997 Ala]a]1an .............................. .. 380/49
`
`9/1997 Ross . . . . . . . . . .
`10/1997 Miller et al. .
`
`. . . .. 379/58
`.. 455/33.1
`
`379/58
`
`342/357
`
`References
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`11/1997 Milanie [ al. 11/1997 Timm et al. .
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`U-S- PATENT DOCUMENTS
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`5,689,269
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`11/1997 Norris ..... ..
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`376897882
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`9/1972 Dessa?ly ______________________________ __ 340/53
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`9/1979 Matsumura et al.
`1/1980 Gn?in e161. ..
`
`. . . . . .. 340/32
`343/7 VM
`.... .. 340/32
`
`(List continued on next page.)
`.
`.
`Prlmary Exam‘”e’—Th°maS H' Tm”
`
`4 239 415
`
`12/1980 Blikken . . . . . . .
`
`. . . . . .. 404/75
`
`Assistant Examiner—Da° L~ Phan
`
`4,349,823
`4,543,577
`
`9/1982 Tagami et al. .
`9/1985 Tachibana e161.
`
`343/7 VM (74) Attorney, Agent, or Firm—Mi1d9, Hoffberg &
`340/904
`Maok11n,LLP
`
`4,552,456
`
`11/1985 Endo . . . . . . . . . . . . . .
`
`. . . .. 356/5
`
`4,626,850
`
`’
`
`’
`
`av1
`
`12/1986 Chey .................................. .. 340/903
`gmhd ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~
`_
`31013156“
`342/357
`8/1991 Darne11et";1'_
`5’O43’736
`455 /54_1
`6/1992 Durboraw
`51119304
`11/1992 Takahashi ..................... .. 364/42405
`5,162,997
`2/1993 Lemercier et al. ........... .. 364/424.02
`5,189,612
`2/1993 Adachi et al ..
`364/426.04
`5,189,619
`6/1993 Morietal.
`...... .. 375/1
`5,218,620
`5,223,844 * 6/1993 Mansell et al. .................... .. 342/257
`
`'
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`'
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`'
`
`ABSTRACT
`(57)
`A mobile communications device comprising a location
`sensmg system, producing a location output; a memory,
`storing a set of locations and associated events; a telecom
`munications device, communicating event and location
`information betWeen a remote system and said memory; and
`a processor, processing said location output in Conjunction
`With said stored locations and associated events in said
`memory, to determine a priority thereof,
`
`43 Claims, 2 Drawing Sheets
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`29
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`Processor 11‘
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`Moblle Communicatmns Device 1
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`Database 5
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`Acouslrc coupler 22 E
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`Satellite dish 17
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`Database
`20
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`\_
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`1
`
`

`
`US 6,252,544 B1
`Page 2
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`US. PATENT DOCUMENTS
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`5,701,328 * 12/1997 Schuchman et a1. .............. .. 375/204
`27327;;
`31332 gokfhyaina t~~~~1~~~~
`33%;
`m1 ,
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`,
`578387237
`11/1998 Reven et a1‘ "
`340/573
`
`6/1999 Smith ................................. .. 340/438
`5,914,654
`5,916,300 * 6/1999 Kirk 6161.
`. 701/213
`5955973 * 9/1999 Anderson
`_ 340/988
`5,983,158
`11/1999 Suzuki et a1. ...................... .. 701/209
`.
`5,987,381
`11/1999 OshlZaWa ........................... .. 701/209
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`5,845,227
`5,862,509
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`12/1998 Peterson .... ..
`.. 701/209
`1/1999 Desai et a1. ........................ .. 701/209
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`_
`_
`* cured by examlner
`
`2
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`

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`U.S. Patent
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`
`U.S. Patent
`
`Jun. 26, 2001
`
`Sheet 2 0f 2
`
`US 6,252,544 B1
`
`Proximity 101
`
`Prospective
`Conjunction 102
`
`Type of event 103
`
`Type of event and
`sensed condition
`104
`
`Unit ‘D 201 Location Codes
`202
`203
`
`W1
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`W2
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`W3
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`Fig. 2
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`W4
`
`High
`priority
`messages
`204
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`Itinerary
`205
`
`Memory dump
`string 206
`
`Event 301
`Location 302
`Time 303
`Source 304
`Expiration 305
`Reliability 306
`Message 307
`
`_
`Flg. 3
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`4
`
`

`
`US 6,252,544 B1
`
`1
`MOBILE COMMUNICATION DEVICE
`
`The present application claims the bene?t of priority
`from US. Provisional Patent Application Ser. No. 60/072,
`757, the entirety of Which is incorporated herein by refer
`ence.
`
`FIELD OF THE INVENTION
`
`The present invention relates to the ?eld of communica
`tions devices, and more particularly to mobile telecommu
`nications devices having position detection and event stor
`age memory.
`
`BACKGROUND OF THE INVENTION
`
`A number of devices are knoWn Which provide mobile
`telecommunication capabilities. Further, knoWn position
`detection systems employ the knoWn Global Positioning
`System (GPS), Global Orbiting Navigational System
`(GLONASS), Loran, RF triangulation, inertial frame refer
`ence and Cellular Telephone base site, e.g., time difference
`of arrival (TDOA) or nearest antenna proximity systems.
`KnoWn GPS mobile systems include memory to record
`location, time and event type, and some systems may be
`integrated With global information systems, to track path,
`speed, etc. KnoWn Differential GPS (DGPS) systems
`include mobile telecommunication functionality to commu
`nicate betWeen distant units, typically to alloW very precise
`relative position measurements, in the presence of substan
`tial absolute position errors, or to calibrate the position of a
`mobile transceiver based on a relative position With respect
`to a ?xed transceiver having a knoWn location. These
`systems do not typically intercommunicate event informa
`tion betWeen units. Thus, the communications streams relate
`to position information only. HoWever, knoWn Weather
`balloon transceiver systems, for example, do transmit both
`position and Weather information to a base station.
`Many electronic location determination systems are
`available, or have been proposed, to provide location infor
`mation to a user equipped With a location determination
`receiver. Groundbased location determination systems, such
`as Loran, Omega, TACAN, Decca, U.S. Airforce Joint
`Tactical Information Distribution System (JTIDS Relnav),
`or US. Army Position Location and Reporting System
`(PLRS), use the intersection of hyperbolic surfaces to pro
`vide location information. Arepresentative ground system is
`LORAN-C discussed in LORAN-C User Handbook,
`Department of Transportation, US. Coast Guard, Comman
`dant Instruction M16562.3, May 1990, Which is incorpo
`rated by reference herein. LORAN-C provides a typical
`location accuracy of approximately 400 meters. Alimitation
`of a LORAN-C location determination system is that not all
`locations in the northern hemisphere, and no locations in the
`southern hemisphere, are covered by LORAN-C. A second
`limitation of LORAN-C is that the typical accuracy of
`approximately 400 meters is insuf?cient for many applica
`tions. A third limitation of LORAN-C is that Weather, local
`electronic signal interference, poor crossing angles, closely
`spaced time difference hyperbolas, and skyWaves (multipath
`interference) frequently cause the accuracy to be signi?
`cantly Worse than 400 meters.
`Other ground-based location determination devices use
`systems that Were developed primarily for communications,
`such as cellular telephone, FM broadcast, and AM broad
`cast. Some cellular telephone systems provide estimates of
`location, using comparison of signal strengths from three or
`more sources. FM broadcast systems having subcarrier
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`signals can provide estimates of location by measuring the
`phases of the subcarrier signals. Kelley et al. in US. Pat. No.
`5,173,710 disclose a system that alloWs determination of a
`location of a vehicle. FM subcarrier signals are received
`from three FM radio stations With knoWn locations but
`unknoWn relative phases by signal processors at the vehicle
`as Well as at a ?xed station having a knoWn location. The
`?xed station processor determines the relative phase of the
`signals transmitted by the three FM radio stations and
`transmits the relative phase information to the vehicle. The
`vehicle processor determines its location from the FM
`subcarrier signal phases and from the relative phase infor
`mation it receives. A limitation of cellular systems and FM
`subcarrier systems for location determination is that they are
`limited to small regions, With diameters of the order of
`20—50 km.
`Satellite-based location determination systems such as
`GPS and GLONASS, use the intersection of spherical sur
`face areas to provide location information With a typical
`(selective availability) accuracy of 100 meters, anyWhere on
`or near the surface of the earth. These systems may also be
`used to obtain positional accuracies Within 1 centimeter. The
`satellite-based location determination systems include sat
`ellites having signal transmitters to broadcast location infor
`mation and control stations on earth to track and control the
`satellites. Location determination receivers process the sig
`nals transmitted from the satellites and provide location
`information to the user.
`The Global Positioning System (GPS) is part of a satellite
`navigation system developed by the United States Defense
`Department under its NAVSTAR satellite program. A fully
`operational GPS includes up to 24 satellites approximately
`uniformly dispersed around six circular orbits With four
`satellites each, the orbits being inclined at an angle of 55°,
`relative to the equator, and being separated from each other
`by multiples of 60° longitude. The orbits have radii of
`26,560 kilometers and are approximately circular. The orbits
`are non-geosynchronous, With 0.5 sidereal day (11.967
`hours) orbital time intervals, so that the satellites move With
`time, relative to the Earth beloW. Theoretically, four or more
`GPS satellites Will have line of sight to most points on the
`Earth’s surface, and line of sight access to three or more such
`satellites can be used to determine an observer’s position
`anyWhere on the Earth’s surface, 24 hours per day. Each
`satellite carries a cesium or rubidium atomic clock to
`provide timing information for the signals transmitted by the
`satellites. Internal clock correction is provided for each
`satellite clock.
`A second con?guration for global positioning is
`GLONASS, placed in orbit by the former Soviet Union and
`noW maintained by the Russian Republic. GLONASS also
`uses 24 satellites, distributed approximately uniformly in
`three orbital planes of eight satellites each. Each orbital
`plane has a nominal inclination of 648° relative to the
`equator, and the three orbital planes are separated from each
`other by multiples of 120° longitude. The GLONASS cir
`cular orbits have smaller radii, about 25,510 kilometers, and
`a satellite period of revolution of 8/17 of a sidereal day (11.26
`hours). A GLONASS satellite and a GPS satellite Will thus
`complete 17 and 16 revolutions, respectively, around the
`Earth every 8 sidereal days. The signal frequencies of both
`GPS and GLONASS are in L-band (1 to 2 GHZ).
`Because the signals from the satellites pass through the
`troposphere for only a short distance, the accuracy of
`satellite location determination systems such as GPS or
`GLONASS is largely unaffected by Weather or local anoma
`lies. Alimitation of GLONASS is that it is not clear that the
`
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`

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`US 6,252,544 B1
`
`3
`Russian Republic has the resources to complete and to
`maintain the system for full World Wide 24 hour coverage.
`The inherent accuracy of the GPS position measured by a
`commercial GPS receiver is approximately 20 meters.
`HoWever, the United States Government currently intention
`ally degrades the accuracy of GPS computed positions for
`commercial users With Selective Availability, SA. With SA,
`the GPS position accuracy of a commercial GPS receiver is
`approximately 100 meters. HoWever, higher accuracy is
`available With the use of secret decryption codes.
`Differential Global Positioning System, DGPS, is a tech
`nique for enhancing the accuracy of the GPS position, and
`of course may be applied to GLONASS as Well. The DGPS
`comprises the Global Positioning System together With a
`GPS reference station receiver situated at a knoWn position.
`DGPS error correction information is derived by taking the
`difference betWeen the measurements made by the GPS
`reference station and the expected measurement at the
`knoWn position of the reference station. DGPS error cor
`rection information can be in the form of GPS satellite
`pseudorange offsets or GPS position offsets. If GPS position
`offsets are used, the GPS satellites used in the calculation of
`the GPS position must be included as part of the DGPS error
`correction information. A processor in a “differential-ready”
`GPS receiver applies the DGPS error correction information
`to enhance the GPS position to an accuracy in the range of
`10 meters to a less than one meter.
`TWo types of DGPS exist, postprocessed and realtime. In
`postprocessed systems, the DGPS error correction informa
`tion and a user’s GPS position information are processed
`after the user has completed his data acquisition. In realtime
`systems, the DGPS error correction information is transmit
`ted to the GPS user in a DGPS telemetry stream, e.g., a radio
`Wave signal, and processed by a differential-ready GPS
`receiver as the application progresses. Realtime processing
`is desirable for many applications because the enhanced
`accuracy of DGPS is available to the GPS user While in the
`?eld. Realtime broadcast of DGPS error correction infor
`mation is available from many sources, both public and
`private, including Coast Guard RDF beacon and commer
`cially operated FM broadcast subcarriers. A DGPS radio
`Wave receiver is required to receive the DGPS radio Wave
`signal containing the DGPS error correction information,
`and pass the DGPS error corrections to the differential-ready
`GPS receiver.
`Many applications of GPS including mineral surveying,
`mapping, adding attributes or features to maps, ?nding sites
`on a map, vehicle navigation, airplane navigation, marine
`navigation, ?eld asset management, geographical informa
`tion systems, and others require the enhanced accuracy that
`is available With DGPS. For instance, a 20 to 100 meter error
`could lead to unintentional trespassing, make the return to an
`underground asset difficult, or put a user on the Wrong block
`While Walking or driving in a city. These applications require
`a computer to store and process data, retain databases,
`perform calculations, display information to a user, and take
`input from a user entry. For instance, the user may need to
`store a map database, display a map, add attributes to
`features on the map, and store these attributes for geographi
`cal information. The user may also need to store and display
`locations or calculate range and bearing to another location.
`GPS is typically used by many professionals engaged in
`navigation and surveying ?elds such as marine navigation,
`aircraft piloting, seismology, boundary surveying, and other
`applications Where accurate location is required or Where the
`cost of GPS is small compared to the cost of a mistake in
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`determining location. Some mobile professionals in the
`utilities, insurance, ranching, prospecting, ambulance
`driving, trucking, delivery, police, ?re, real estate, forestry,
`and other mobile applications use GPS to save time in their
`Work. GPS is also used for personal travel such as hiking,
`biking, horseback riding, yachting, ?shing, driving in per
`sonal cars, and other travel activities. To enhance the use
`fulness of GPS a number of sources have integrated maps
`into the output, or provide a global information system (GIS)
`to process the GPS output. Thus, it is knoWn to sort and
`display proximate map features and/or attributes in the same
`coordinate system as the position information.
`As disclosed in US. Pat. No. 5,528,248, incorporated
`herein by reference, a satellite location determination system
`using Global Positioning System (GPS) satellite signal
`transmitters receives a spread spectrum L1 carrier signal
`having a frequency=1575.42 MHZ. The L1 signal from each
`satellite signal transmitter is binary phase shift key (BPSK)
`modulated by a Coarse/Acquisition (C/A) pseudo-random
`noise (PRN) code having a clock or chip rate of f0=1.023
`MHZ. Location information is transmitted at a rate of 50
`baud. The PRN codes alloW use of a plurality of GPS
`satellite signal transmitters for determining an observer’s
`position and for providing location information. A signal
`transmitted by a particular GPS satellite is selected by
`generating and correlating the PRN code for that particular
`satellite signal transmitter With a GPS signal received from
`that satellite. All C/A PRN codes used for GPS satellite
`signals are knoWn and are stored and/or generated in a GPS
`receiver. A bit stream from the GPS satellite signal trans
`mitter includes an ephemeris location of the GPS satellite
`signal transmitter, an almanac location for all GPS satellites,
`and correction parameters for ionospheric signal propaga
`tion delay, and clock time of the GPS satellite signal
`transmitter. Accepted methods for generating the C/A-code
`are set forth in the document GPS Interface Control Docu
`ment ICD-GPS-200, published by RockWell International
`Corporation, Satellite Systems Division, Revision A, Sep.
`26, 1984, Which is incorporated by reference herein.
`Energy on a single carrier frequency from all of the
`satellites is transduced by the receiver at a point close to
`Earth. The satellites from Which the energy originated are
`identi?ed by modulating the carrier transmitted from each
`satellite With pseudorandom type signals. In one mode,
`referred to as the coarse/acquisition (C/A) mode, the pseu
`dorandom signal is a gold code sequence having a chip rate
`of 1.023 MHZ; there are 1,023 chips in each gold code
`sequence, such that the sequence is repeated once every
`millisecond (the chipping rate of a pseudorandom sequence
`is the rate at Which the individual pulses in the sequence are
`derived and therefore is equal to the code repetition rate
`divided by the number of members in the code; one pulse of
`the noise code is referred to as a chip).
`The 1.023 MHZ gold code sequence chip rate enables the
`position of the receiver responsive to the signals transmitted
`from four of the satellites to be determined to an accuracy of
`approximately 60 to 300 meters.
`There is a second mode, referred to as the precise or
`protected (P) mode, Wherein pseudorandom codes With chip
`rates of 10.23 MHZ are transmitted With sequences that are
`extremely long, so that the sequences repeat no more than
`once per Week. In the P mode, the position of the receiver
`can be determined to an accuracy of approximately 16 to 30
`meters. HoWever, the P mode requires Government classi
`?ed information about hoW the receiver is programmed and
`is intended for use only by authoriZed receivers. Hence,
`civilian and/or military receivers that are apt to be obtained
`by unauthoriZed users are not responsive to the P mode.
`
`6
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`

`
`US 6,252,544 B1
`
`5
`To enable the receivers to separate the C/A signals
`received from the different satellites, the receiver includes a
`plurality of different locally derived gold code sources, each
`of Which corresponds With the gold code sequence trans
`mitted from one of the satellites in the ?eld of the receiver.
`The locally derived and the transmitted gold code sequences
`are cross correlated With each other over one millisecond,
`gold code sequence intervals. The phase of the locally
`derived gold code sequences vary on a chip-by-chip basis,
`and then Within a chip, until the maximum cross correlation
`function is obtained. Since the cross correlation for tWo gold
`code sequences having a length of 1,023 bits is approxi
`mately 16 times as great as the cross correlation function of
`any of the other combinations of gold code sequences, it is
`relatively easy to lock the locally derived gold code
`sequence onto the same gold code sequence that Was trans
`mitted by one of the satellites.
`The gold code sequences from at least four of the satellites
`in the ?eld of vieW of the receiver are separated in this
`manner by using a single channel that is sequentially respon
`sive to each of the locally derived gold code sequences or by
`using parallel channels that are simultaneously responsive to
`the different gold code sequences. After four locally derived
`gold code sequences are locked in phase With the gold code
`sequences received from four satellites in the ?eld of vieW
`of the receiver, the position of the receiver can be deter
`mined to an accuracy of approximately 60 to 300 meters.
`The approximately 60 to 300 meter accuracy of GPS is
`determined by (1) the number of satellites transmitting
`signals to Which the receiver is effectively responsive, (2)
`the variable amplitudes of the received signals, and (3) the
`magnitude of the cross correlation peaks betWeen the
`received signals from the different satellites.
`In response to reception of multiple pseudorange noise
`(PRN) signals, there is a common time interval for some of
`the codes to likely cause a degradation in time of arrival
`measurements of each received PRN due to the cross
`correlations betWeen the received signals. The time of
`arrival measurement for each PRN is made by determining
`the time of a peak amplitude of the cross correlation betWeen
`the received composite signal and a local gold code
`sequence that is identical to one of the transmitted PRN.
`When random noise is superimposed on a received PRN,
`increasing the averaging time of the cross correlation
`betWeen the signal and a local PRN sequence decreases the
`average noise contribution to the time of arrival error.
`HoWever, because the cross correlation errors betWeen the
`received PRN’s are periodic, increasing the averaging time
`increases both signal and the cross correlation value betWeen
`the received PRN’s alike and time of arrival errors are not
`reduced.
`The GPS receiver may incorporate a Kalman ?lter, Which
`is adaptive and therefore automatically modi?es its thresh
`old of acceptable data perturbations, depending on the
`velocity of the vehicle (GPS antenna). This optimiZes sys
`tem response and accuracy of the GPS system. Generally,
`When the vehicle increases velocity by a speci?ed amount,
`the GPS Kalman ?lter Will raise its acceptable noise thresh
`old. Similarly, When the vehicle decreases its velocity by a
`speci?ed amount, the GPS Kalman ?lter Will loWer its
`acceptable noise threshold.
`Extremely accurate GPS receivers depend on phase mea
`surements of the radio carriers that they receive from various
`orbiting GPS satellites. Less accurate GPS receivers simply
`develop the pseudoranges to each visible satellite based on
`the time codes being sent. Within the granularity of a single
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`15
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`25
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`35
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`time code, the carrier phase can be measured and used to
`compute range distance as a multiple of the fundamental
`carrier Wavelength. GPS signal transmissions are on tWo
`synchronous, but separate, carrier frequencies “L1” and
`“L2”, With Wavelengths of nineteen and tWenty-four
`centimeters, respectively. Thus Within nineteen or tWenty
`four centimeters, the phase of the GPS carrier signal Will
`change 360° (2n radians). HoWever, the number of Whole
`cycle (360°) carrier phase shifts betWeen a particular GPS
`satellite and the GPS receiver must be resolved. At the
`receiver, every cycle Will appear essentially the same, over
`a short time frame. Therefore there is an “integer ambiguity”
`in the calculation. The resolution of this integer ambiguity is
`therefore a calculation-intensive arithmetic problem to be
`solved by GPS receivers. The traditional approaches to such
`integer ambiguity resolution have prevented on-the-?y solu
`tion measurement updates for moving GPS receivers With
`centimeter accurate outputs. Very often, such highly accu
`rate GPS receivers have required long periods of motion
`lessness to produce a ?rst and subsequent position ?x.
`There are numerous prior art methods for resolving inte
`ger ambiguities. These include integer searches, multiple
`antennas, multiple GPS observables, motion-based
`approaches, and external aiding. Search techniques often
`require signi?cant computation time and are vulnerable to
`erroneous solutions or When only a feW satellites are visible.
`More antennas can improve reliability considerably. If car
`ried to an extreme, a phased array of antennas results,
`Whereby the integers are completely unambiguous and
`searching is unnecessary. But for economy, reduced siZe,
`complexity and poWer consumption, the minimum number
`of antennas required to quickly and unambiguously resolve
`the integers, even in the presence of noise, is preferred.
`One method for integer resolution is to make use of the
`other observables that modulate a GPS timer. The pseudo
`random code imposed on the GPS satellite transmission can
`be used as a coarse indicator of differential range, although
`it is very susceptible to multipath problems. Differentiating
`the L1 and L2 carriers in phase sensitive manner provides a
`longer effective Wavelength, and reduces the search space,
`i.e., an ambiguity distance increased from 19 or 24 centi
`meters to about 456 centimeters. HoWever, dual frequency
`receivers are expensive because they are more complicated.
`Motion-based integer resolution methods make use of addi
`tional information provided by platform or satellite motion.
`But such motion may not alWays be present When it is
`needed. Another prior art technique for precision attitude
`determination and kinematic positioning is described by
`Hatch, in US. Pat. No. 4,963,889, incorporated herein by
`reference, Which employs tWo spaced antennas, moveable
`With respect to each other. Knight, US. Pat. No. 5,296,861,
`incorporated herein by reference, provides a method of
`reducing the mathematical intensity of integer ambiguity
`resolution. See also, US. Pat. No. 5,471,218, incorporated
`herein by reference.
`Direct range measurements, combined With the satellite
`geometry, may also alloW the correct integer carrier phase
`ambiguities to be determined for a plurality of satellites
`tracked at tWo or more sites. The use of additional sensors,
`such as a laser level, electronic distance meter, a compass,
`a tape, etc., provide valuable constraints that limit the
`number of possible integer ambiguities that need to be
`considered in a search for the correct set.
`Many systems using handheld computers, having soft
`Ware and databases de?ning maps and running standard
`operating systems, have been coupled to GPS Smart Anten
`nas. Wireless, infrared, serial, parallel, and PCMCIA inter
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`US 6,252,544 B1
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`7
`faces have been used to interconnect the handheld computer
`and the GPS Smart Antenna. Differential-ready GPS Smart
`Antennas having an input to receive signals representative of
`DGPS error corrections are also commercially available.
`Further, GPS receivers and Differential-ready GPS Smart
`Antennas Which are self contained, built onto a type II
`PCMCIA card (PC Card), and/or having serial data com
`munications ports (RS-232 or RS-422) are commercially
`available. See, US. Pat. No. 5,276,451, and US. Pat. No.
`5,210,540, assigned to Pioneer Electronic Corporation.
`There are several different types of vehicle navigational
`systems. The ?rst system makes use of stored map displays
`Wherein the maps of a predetermined area are stored in the
`in-vehicle computer and displayed to the vehicle operator or
`driver. The maps, combined With information describing the
`location Where the vehicle started and Where it is to go, Will
`highlight the direction and the driver Will have to read the
`display and folloW the route. One such stored map display
`system Was offered by General Motors on their 1994
`Oldsmobile, using Global Positioning System (GPS) satel
`lites and dead reckoning techniques, and likely map match
`ing to determine a precise location. The vehicle has radio
`receivers for receiving data from satellites, giving the loca
`tion of the receiver expressed in latitude and longitude. The
`driver enters details of the desired destination into an
`on-board or in-vehicle computer in the form of speci?c
`address, a road intersection, etc. The stored map is
`displayed, alloWing the operator to pinpoint the desired
`destination. The on-board computer then seeks to calculate
`the most ef?cient route, displaying the distance to, and the
`direction of, each turn using graphics and a voice prompt.
`Other knoWn systems employ speech recognition as a user
`input. For example, another system, described in US. Pat.
`No. 5,274,560 does not use GPS and has no sensing devices
`connected to the vehicle. The routing information is con
`tained in a device that is coupled to a CD player in the
`vehicle’s audio system. Commands are entered into the
`system via a microphone and the results are outputted
`through the vehicle’s speakers. The vehicle operator spells
`out the locations and destinations, letter by letter. The system
`con?rms the locations by repeating Whole Words. Once the
`system has received the current location and destination, the
`system develops the route and calculates the estimated time.
`The operator utiliZes several speci?c performance
`commands, such as “Next”, and the system then begins to
`give segment by segment route directions.
`Still another system, such as the Siemens Ali-ScoutTM
`system, requires that the driver key-in the destination
`address coordinates into the in-vehicle computer. Acompass
`located in the vehicle then gives a “compass” direction to the
`destination address. Such a compass direction is shoWn in
`graphics as an arroW on a display unit, indicating the
`direction the driver should go. Along the side of the road are
`several infrared beacon sites Which transmit data informa
`tion to a properly equipped vehicle relative to the next
`adjacent beacon site. From all of the information received,
`the in-vehicle computer selects the desired beacon data
`information to the next beacon and displays a graphic
`symbol for the vehicle operator to folloW and the distance to
`the desired destination. In this system, there is no map to
`read; both a simple graphic symbol and a segment of the
`route is displayed, and a voice prompt telling the vehicle
`operator When to turn and When to continue in the same
`direction is enunciated. Once the program begins, there is
`minimal operator feedback required.
`US. Pat. No. 4,350,970, describes a method for traf?c
`manageme