United States Patent 19
`Vaughn
`
`54 VEHICLE SPEED CONTROL BASED ON
`GPS/MAP MATCHING OF POSTED SPEEDS
`
`75 Inventor: David Vaughn, San Jose, Calif.
`73) Assignee: Trimble Navigation Limited,
`Sunnyvale, Calif.
`21 Appl. No.: 325,130
`22 Filed:
`Nov. 21, 1994
`
`6
`
`- a
`-
`-
`- - - - -
`a
`a
`: s
`(52) U.S. Cl. ..........................
`s
`58) Field of Search ..................................... 342/357, 457;
`364/449, 440
`
`34I 2. SSi.
`7; 364/440
`
`56
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`- - 353,
`- -
`a
`3. SE -
`:
`... 356/375
`4,818, 107 4f1989 Ono et al. ...........
`5,179,519
`1/1993 Adachi et al. .......................... 364/449
`
`- -
`
`-
`
`- - - -
`
`IIIHIH III
`USOO5485 161A
`11
`Patent Number:
`5,485,161
`(45) Date of Patent:
`Jan. 16, 1996
`
`5,270,708 12/1993 Kanishina ............................. 340/995
`5,311,173
`5/1994 Komura et al. ......................... 364449
`5,343,780 9/1994 McDaniel et al. ...................... 477/108
`Primary Examiner-Theodore M. Blum
`Attorney, Agent, or Firm-Boris G. Tankhilevich
`57
`ABSTRACT
`The GPS-map speed matching system for controlling the
`speed of the vehicle is described. The system includes a GPS
`navigation receiver, a database processing facility, a GPS
`computer, an engine computer, a video display, a speed
`sensor and a heading sensor. The database processing facil
`ity can be local or remote. The GPS computer obtains the
`latitude, longitude, heading and speed of the vehicle. The
`database processing facility processes the GPS data and
`obtains the location and the maximum posted speed of the
`vehicle. The GPS computer or an engine computer perform
`the comparison between the vehicle speed and the maximum
`posted speed and signal the odometer to decrease the vehicle
`speed if the vehicle speed exceeds the maximum posted
`speed plus some predetermined value.
`
`26 Claims, 3 Drawing Sheets
`
`SAELTE
`VEHICLES
`
`“PP
`a - N34
`\
`f
`X32
`28 y
`30 \?/
`
`-a
`GPSTRANSM
`ANDESElyING
`
`:
`
`47
`
`Z
`
`------ 242
`
`d
`OC
`LOCAL
`PESESs
`
`FACTY
`
`36
`
`38
`
`39
`
`GPS
`ANTENNA
`
`GPS
`AMP
`
`TRACKING
`LOOPS
`
`48
`
`DOWNLOAD
`PORT
`
`WEHICLE
`ODOMETER
`
`E.
`
`GPS
`MEMORY
`UNT
`
`24
`
`SPEED
`SENSOR
`
`HEADING
`SENSOR
`
`ALARM
`SYSTEM
`
`2O
`
`14
`
`ENGINE
`
`
`
`WEHICLE
`ENGINE
`MICRO
`PROCESSOR
`
`22
`
`i8
`
`:
`
`c5SE
`
`MPUTER
`MEMORY
`
`1 WEHICLE ENGINE
`15- - -
`COMPUTER
`
`2
`
`WEHICLE
`DISPLAY OF
`EECTRONIC
`MAP
`
`
`
`GPS
`MICRO
`PROCESSOR
`
`GPS
`COMPUTER
`
`UNIFIED PATENTS EXHIBIT 1027
`Page 1 of 12
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`

`

`U.S. Patent
`
`Jan. 16, 1996
`
`Sheet 1 of 3
`
`5,485,161
`
`SATELLITE
`VEHICLES
`
`47
`
`42
`
`
`
`\ 'Y 34
`f V/
`281 \
`/Y 32
`/
`301N /
`W
`
`GPSTRANSMIT
`AND RECEIVINGs a
`MEANS
`
`:
`
`/ O
`LOCAL
`DATABASE
`- PRSie
`FACILITY
`
`36
`
`38
`
`39
`
`GPS
`ANTENNA
`
`GPS
`AMP
`
`TRACKING
`LOOPS
`
`48
`
`DOWNLOAD
`PORT
`
`VEHICLE
`ODOMETER
`
`24
`
`SENSOR
`
`HEADING
`SENSOR
`
`ALARM
`SYSTEM
`
`26
`
`
`
`
`
`
`
`22
`
`VEHICLE
`ENGINE
`MICRO
`PROCESSOR
`
`2O
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`18
`
`ENGINE
`
`
`
`
`
`ENGINE
`COMPUTER
`MEMORY
`UNIT
`
`15- - -
`
`VEHICLE ENGINE
`COMPUTER
`
`10
`
`FIG. f
`
`12
`
`
`
`VEHICLE
`DISPLAY OF
`ELETEONIC
`
`C
`
`GPS
`MEMORY
`UNIT
`
`I/O
`BUS
`
`
`
`GPS
`MICRO
`PROCESSOR
`
`GPS
`COMPUTER
`
`UNIFIED PATENTS EXHIBIT 1027
`Page 2 of 12
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`

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`U.S. Patent
`
`Jan. 16, 1996
`
`Sheet 2 of 3
`
`5,485,161
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`REMOTE
`DATABASE
`PROCESSING
`FACLITY
`
`RECEIVING AND
`TRANSMITTIN
`MEANS G
`
`
`
`LAT-LON,
`BEARING, SPEED
`8 f
`
`LATON
`COMPUTER
`INDEXER
`
`MAP DATA
`
`STREET
`HERARCHY
`DATABASE
`
`
`
`LAND MARKS
`DAABASE
`
`STREET
`SIGNAL
`DATABASE
`
`SPEED
`LIMIT
`DATABASE
`
`INTERSECTION
`DATABASE
`
`9C)
`
`JURISDICTION
`DAABASE
`
`UNIFIED PATENTS EXHIBIT 1027
`Page 3 of 12
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`

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`U.S. Patent
`
`Jan. 16, 1996
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`Sheet 3 of 3
`
`5,485,161
`
`ff O
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`
`
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`
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`
`
`
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`
`
`
`
`OBTAINING LAT-LON, SPEED AND
`BEARING USING GPS COMPUTER
`
`130
`
`
`
`OBTAINING
`SPEED AND
`HEADING OF
`VEHICLE USING
`SENSORS
`
`
`
`140
`
`TRANSMITTING DATA FROM
`GPS TO DATABASE FACILITY
`
`
`
`
`
`
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`150
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`PROCESSING THE GPS DATA
`AND OBTAINING MAX SPEED DATA
`
`16O
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`TRANSMITTING MAP DATA TO
`GPS AND ENGINE COMPUTERS
`
`
`
`
`
`IS .
`VEHICLE'S SPEED
`GREATER THAN
`MAP SPEED
`
`YES
`
`18O
`
`GPS OR ENGINE COMPUTER
`DECREASES SPEED OF VEHICLE
`
`FIG.4
`
`UNIFIED PATENTS EXHIBIT 1027
`Page 4 of 12
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`

`1.
`VEHICLE SPEED CONTROL BASED ON
`GPS/MAP MATCHING OF POSTED SPEEDS
`
`5,485,161
`
`2
`speed of the vehicle is controlled and the posted speed is
`enforced without using the police patrol.
`One aspect of the present invention is directed to an
`apparatus for controlling the maximum speed of a vehicle
`based on the speed limits posted on the street on which the
`vehicle is travelling. The apparatus includes a GPS naviga
`tion computer and receiver with an earth navigation format
`data output, a vehicle engine computer connected to said
`navigation computer, and a map database. The GPS navi
`gation computer includes a GPS associated memory unit.
`The GPS navigation computer includes a port for down
`loading map data from the map database into the memory
`unit for original installation and for updating and changes.
`The GPS navigation computer determines location and
`speed of the vehicle, inputs the maximum speed from the
`map database, and forwards the speed limit to the engine
`computer, wherein the engine computer uses the speed limit
`information contained in the map database to limit the
`maximum ground speed of the vehicle. The apparatus fur
`ther includes a vehicle display of an electronic map con
`nected to the GPS computer for electronically displaying the
`map with the posted speed limit, the current location of the
`vehicle on the map and the current speed of the vehicle.
`The apparatus further includes a speed sensor and a
`heading sensor. These sensors are connected to the vehicle
`odometer for reading speed and heading of the vehicle and
`to the GPS computer and to the vehicle engine computer for
`transmitting the reading of speed and heading of the vehicle.
`The vehicle engine computer further includes an engine
`computer memory and an engine microprocessor, wherein
`said vehicle engine computer is connected to the GPS
`computer to receive the value of the maximum map speed
`limit from the map data.
`In one embodiment the engine computer memory contains
`a predetermined speed value which is added to the maxi
`mum speed map limit to obtain the real maximum speed
`value of the vehicle. The vehicle engine computer is con
`nected to the vehicle odometer to control the real maximum
`speed value of the vehicle.
`In another embodiment the GPS memory unit contains a
`predetermined speed value which is added to the maximum
`speed map limit to obtain the real maximum speed value of
`the vehicle. The GPS computer is connected to the vehicle
`engine computer to control the real maximum speed value of
`the vehicle.
`In one embodiment the map database includes a local
`database processing facility connected to the port by a hard
`wired connection for downloading map data from one
`particular database. It is connected to the GPS computer by
`a hard wired connection for receiving longitude, latitude,
`speed and bearing of the vehicle. The database processing
`facility comprises a plurality of specialized databases that
`include relational data expressed in earth navigation format,
`an indexer connected to specialized databases for selecting
`access to a particular database according to the position
`descriptor related in this particular database to the vehicle
`location, wherein the vehicle location and speed are deter
`mined by the GPS computer and are transmitted to the
`database processing facility. The plurality of specialized
`databases further includes data for relational access that is in
`a latitude and longitude format.
`In another embodiment the database processing facility
`includes a remote database processing facility. In this
`embodiment, the GPS computer further includes a GPS
`transmitting means for a wireless transmission of the posi
`tion, speed and bearing data of the vehicle to the remote
`
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`BACKGROUND
`When a vehicle travels the road with the posted speed
`limit, it is often appropriate to monitor adherence by the
`vehicle to the posted maximum speed. The adherence does
`not have to be a strict one. It is sufficient for the vehicle to
`travel within five-ten miles/hour of the posted maximum
`speed. Usually the maximum posted speed is enforced by the
`police road patrol.
`Monitoring adherence by the vehicle to a route or sched
`ule is well known in the prior art.
`Gray in U.S. Pat. No. 4,651,157 discloses a security
`monitoring and tracking system for a terrestrial or marine
`vehicle that uses navigational information to determine the
`latitude and longitude of the vehicle.
`U.S. Pat. No. 4,814,711, issued to Olsen, discloses a
`survey system for collection of real time data from a
`plurality of survey vehicles, each of which determines its
`present location using global positioning system (GPS)
`signals received from a plurality of GPS satellites. A central
`station periodically polls each survey vehicle and receives
`that survey vehicle's present location coordinates by radio
`wave communication. The central station compares that
`vehicle's path with a survey pattern assigned to that vehicle.
`The geophysical data measured by a vehicle are also
`received by the central station and are coordinated with that
`vehicle's location at the time it was taken.
`Harker discloses in U.S. Pat. No. 5,177,684 a method for
`analyzing transportation schedules of a transportation
`vehicle to produce optimized schedules. The method uses
`information on the vehicle's assigned path and the average
`speed and mobility of the vehicle, and determines arealistic,
`optimum schedule, including arrival and departure times,
`that the vehicle can adhere to along that path.
`U.S. Pat. No. 5,243,530 issued to Stanifer discloses a
`system for tracking a plurality of terrestrial, marine or
`airborne vehicles, using a local area network and packet
`communication of location information. Loran-C signals are
`received by a receiver/processor/transmitter on a vehicle, the
`vehicle's present location is determined, and this location
`information is transmitted to a central station, using LAN
`45
`packet protocols, acknowledgment signals and backoff/re
`transmission procedures that are standard in the LAN art. If
`a given vehicle's present location is not received by the
`central station within a time interval of selected length, the
`central station requests transmission of the present location
`from that vehicle.
`What is needed is an approach that allows one to auto
`matically match the vehicle's speed with the maximum
`posted speed and to control the vehicle's speed if it sub
`stantially exceeds the posted limit. It would allow enforce
`ment of the vehicle's maximum speed without the police
`patrol or with reduced police patrol, which is of interest to
`owners of fleets of vehicles, such as trucking companies.
`Such compliance would save the fleet owners money.
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`SUMMARY
`The present invention is unique because it allows one to
`control the vehicle speed by using the Global Positioning
`System to determine the vehicle location, and to use locally
`stored map database to match the vehicle location and speed
`with the maximum posted speed limit. Accordingly, the
`
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`3
`database processing facility. The remote database processing
`facility further comprises a receiving means for wireless
`reception of the vehicle position, speed and bearing data,
`and a transmitting means for a wireless transmission of the
`map data corresponding to the position, speed and bearing
`data of the vehicle to the GPS computer. The GPS computer
`further comprises a GPS receiving means for wireless recep
`tion the map data from the remote database processing
`facility and for downloading the map data to the download
`port.
`The wireless transmission and reception of the map data
`can be performed by using the analog cellular phone, a
`cellular digital phone, a satellite link, wherein the satellite
`link includes a Trimble Galaxy system which uses the
`Inmarsat Satellite system, or a Specialized Mobile Radio
`system (SMR).
`Another aspect of the present invention is directed to the
`use of a wireless link for reporting the location, speed and
`the maximum posted speed of the vehicle to the pertinent
`customer service organization.
`One more aspect of the present invention is directed to a
`method for controlling the maximum speed of a vehicle
`based on the speed limits posted on the street on which the
`vehicle is travelling using a remote database processing
`facility. The method comprises the steps of: (1) determining
`the position, speed and bearing data of the vehicle by using
`the GPS computer; (2) transmitting the position, speed and
`bearing data of the vehicle to the remote database processing
`facility by using said GPS transmitting means; (3) receiving
`the vehicle position, speed and bearing data by the remote
`database processing facility employing said receiving
`means; (4) processing the position, speed and bearing data
`by the remote database processing facility to obtain the map
`location of the vehicle; (5) determining the map data includ
`ing the maximum speed corresponding to the location of the
`vehicle by the processing facility; (6) transmitting the map
`and vehicle data corresponding to the position, speed and
`bearing data of the vehicle by the transmitting means of the
`database processing facility; (7) receiving the map and
`vehicle data including the maximum speed for the vehicle
`location from the remote database processing facility by the
`GPS receiving means; (8) downloading the map data to the
`download port; (9) determining what street the vehicle is on
`and what is the maximum speed limit for that street; (10)
`forwarding the maximum speed limit to the engine computer
`by the GPS computer; (11) using the speed limit information
`contained in the map database by said engine computer to
`limit the maximum ground speed of the vehicle; and (12)
`reporting the location, speed of the vehicle and the maxi
`mum posted speed to the customer service organization by
`using the GPS transmitting means.
`Yet one more aspect of the present invention is directed to
`a method for controlling the maximum speed of a vehicle
`based on the speed limits posted on the street on which the
`vehicle is travelling using a local database processing facil
`ity. The method comprises the steps of: (1) determining the
`position, speed and bearing data of the vehicle by using said
`GPS computer; (2) transmitting the position, speed and
`bearing data of the vehicle to the local database processing
`facility; (3) processing the position, speed and bearing data
`by the local database processing facility to obtain the map
`location of the vehicle; (4) determining the map data includ
`ing the maximum speed corresponding to the location of the
`vehicle by the local processing facility; (5) downloading the
`map and vehicle data to the download port; (6) storing the
`map and vehicle data in the memory unit including speed of
`the vehicle, what street the vehicle is on and what is the
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`maximum speed limit for that street; (7) forwarding the
`maximum speed limit to the engine computer by the GPS
`computer; (8) using the map data by said engine computer
`to limit the maximum ground speed of the vehicle; and (9)
`reporting the vehicle speed, location and maximum posted
`speed to the customer service organization using said GPS
`transmitting means.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 illustrates a functional diagram of a GPS-map
`speed matching vehicle.
`FIG. 2 depicts a remote database processing facility with
`a wireless link.
`FIG. 3 shows a functional diagram of the database pro
`cessing facility.
`FIG. 4 illustrates a flow chart showing how the GPS-map
`matching vehicle works.
`
`DETALED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`FIG. 1 illustrates a GPS-map speed matching vehicle with
`a local database processing facility embodiment of the
`present invention, referred to herein by the general reference
`numeral 10. System 10 includes a global positioning system
`(GPS) navigation receiver 38 including a GPS antenna 36.
`In the preferred embodiment, the GPS antenna 36 is able to
`receive the satellite signals from at least four satellite
`vehicles 28, 30, 32 and 34. These four satellites are part of
`the GPS.
`The GPS is a system of satellite signal transmitters, with
`receivers located on the Earth's surface or starting near to
`the Earth's surface compared to the orbit altitude of the GPS
`satellite, that transmits information from which an observ
`er's present location and/or the time of observation can be
`determined. There is also the Global Orbiting Navigational
`System (GLONASS), which operates as an alternative GPS
`system.
`The Global Positioning System (GPS) is part of a satel
`lite-based navigation system developed by the United States
`Defense Department under its NAVSTAR satellite program.
`A fully operational GPS includes up to 24 Earth 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,
`three or more GPS satellites will be visible from most points
`on the Earth's surface, and visual 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.
`Each GPS satellite transmits two spread spectrum, L-band
`carrier signals: an L1 signal having a frequency f1=1575.42
`MHz and an L2 signal having a frequency f2=1227.6 MHz.
`These two frequencies are integral multiplies fl=1540 fo
`and f2=1200 fo of a base frequency fo=1.023 MHz. The L1
`signal from each satellite is binary phase shift key (BPSK)
`modulated by two pseudo-random noise (PRN) codes in
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`S
`phase quadrature, designated as the CIA-code and P(Y)-
`code. The L2 signal from each satellite is BPSK modulated
`by only the P(Y)-code. The nature of these PRN codes is
`described below.
`One motivation for use of two carrier signals L1 and L2
`is to allow partial compensation for propagation delay of
`such a signal through the ionosphere, which delay varies
`approximately as the inverse square of signal frequency f
`(delay-f). This phenomenon is discussed by MacDoran in
`U.S. Pat. No. 4,463,357, which discussion is incorporated by
`reference herein. When transit time delay through the iono
`sphere is determined, a phase delay associated with a given
`carrier signal can also be determined.
`Use of the PRN codes allows use of a plurality of GPS
`satellite signals for determining an observer's position and
`for providing the navigation information. A signal transmit
`ted by a particular GPS satellite is selected by generating and
`matching, or correlating, the PRN code for that particular
`satellite. All PRN codes are known and are generated or
`stored in GPS satellite signal receivers carried by ground
`observers. A first PRN code for each GPS satellite, some
`times referred to as a precision code or P(Y)-code, is a
`relatively long, fine-grained code having an associated clock
`or chip rate of 10 fo=10.23 MHz. A second PRN code for
`each GPS satellite, sometimes referred to as a clearfacqui
`sition code or CIA-code, is intended to facilitate rapid
`satellite signal acquisition and hand-over to the P(Y)-code,
`and is a relatively short, coarser-grained code having a clock
`or chip rate of fo=1.023 MHz. The CIA-code for any GPS
`satellite has a length of 1023 chips or time increments before
`this code repeats. The full P(Y)-code has a length of 259
`days, with each satellite transmitting a unique portion of the
`full P(Y)-code. The portion of P(Y)-code used for a given
`GPS satellite has a length of precisely one week (7.000 days)
`before this code portion repeats. Accepted methods for
`generating the C/A-code and P(Y)-code are set forth in the
`document GPS Interface Control Document ICD-GPS-200,
`published by Rockwell International Corporation, Satellite
`Systems Division, Revision B-PR, 3 Jul. 1991, which is
`incorporated by reference herein.
`The GPS satellite bit stream includes navigational infor
`mation on the ephemeries of the transmitting GPS satellite
`and an almanac for all GPS satellites, with parameters
`providing corrections for ionospheric signal propagation
`delays suitable for single frequency receivers and for an
`offset time between satellite clock time and true GPS time.
`The navigational information is transmitted at a rate of 50
`Baud. A useful discussion of the GPS and techniques for
`obtaining position information from the satellite signals is
`found in The NAVSTAR Global Positioning System, Tom
`50
`Logsdon, Van Nostrand Reinhold, New York, 1992, pp.
`17-90.
`A second alternative configuration for global positioning
`is the Global Orbiting Navigation Satellite System (GLO
`NASS), placed in orbit by the former Soviet Union and now
`55
`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
`anominal inclination of 64.8 relative to the equator, and the
`three orbital planes are separated from each other by mul
`tiples of 120° longitude. The GLONASS circular orbits have
`smaller radii, about 25,510 kilometers, and a satellite period
`of revolution of 9/17 of a sidereal day (1.26 hours). A
`GLONASS satellite and a GPS satellite will thus complete
`17 and 16 revolutions, respectively, around the Earth every
`8 days. The GLONASS system uses two carrier signals L1
`and L2 with frequencies of f1= (1.602+9k/16) GHz and
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`f2=(1.246+7k/16) GHz, where k (=0,1,2,. . . 23) is the
`channel or satellite number. These frequencies lie in two
`bands at 1.597-1.617 GHz (L1) and 1,240-1,260 GHz, (L2).
`The L1 code is modeled by a CIA-code (chip rate=0.511
`MHz) and by a P(Y)-code (chip rate=5.11 MHz). The L2
`code is presently modeled only by the P(Y)-code. The
`GLONASS satellites also transmit navigational data at a rate
`of 50 Baud. Because the channel frequencies are distin
`guishable from each other, the POY)-code is the same, and
`the C/A-code is the same, for each satellite. The methods for
`receiving and analyzing the GLONASS signals are similar
`to the methods used for the GPS signals.
`Reference to a Satellite Positioning System or SATPS
`herein refers to a Global Positioning System, to a Global
`Orbiting Navigation System, and to any other compatible
`satellite-based system that provides information by which an
`observer's position and the time of observation can be
`determined, all of which meet the requirements of the
`present invention.
`A Satellite Positioning System (SATPS), such as the
`Global Positioning System (GPS) or the Global Orbiting
`Navigation Satellite System (GLONASS), uses transmission
`of coded radio signals, with the structure described above,
`from a plurality of Earth-orbiting satellites. A single passive
`receiver of such signals is capable of determining receiver
`absolute position in an Earth-centered, Earth-fixed coordi
`nate reference system utilized by the SATPS.
`A configuration of two or more receivers can be used to
`accurately determine the relative positions between the
`receivers or stations. This method, known as differential
`positioning, is far more accurate than absolute positioning,
`provided that the distances between these stations are sub
`stantially less than the distances from these stations to the
`satellites, which is the usual case. Differential positioning
`can be used for survey or construction work in the field,
`providing location coordinates and distances that are accu
`rate to within a few millimeters.
`In differential position determination, many of the errors
`in the SATPS that compromise the accuracy of absolute
`position determination are similar in magnitude for stations
`that are physically close. The effect of these errors on the
`accuracy of differential position determination is therefore
`substantially reduced by a process of partial error cancella
`tion.
`ASATPSantenna receives SATPS signals from a plurality
`(preferably four or more) of SATPS satellites and passes
`these signals to a SATPS signal receiver/processor, which
`(1) identifies the SATPS satellite source for each SATPS
`signal, (2) determines the time at which each identified
`SATPS signal arrives at the antenna, and (3) determines the
`present location of the SATPS antenna from this information
`and from information on the ephemeries for each identified
`SATPS satellite. The SATPS signal antenna and signal
`receiver/processor are part of the user segment of a particu
`lar SATPS, the Global Positioning System, as discussed by
`Tom Logsdon, op cit, p 33-90.
`There are several major components in a typical GPS
`(SATPS) receiver. The GPS (SATPS) antenna36 is designed
`to pick up the right-hand circular-polarized L1 and/or L2
`carrier waves from Selected Satellites located above the
`horizon. The amplifying circuit 38 concentrates and ampli
`fies the modulated carrier waves, and converts the wave
`electromagnetic energy into an equivalent electric current
`still containing the appropriate C/A-code, P(Y)-code, and
`data stream modulations.
`Two different types of tracking loops 39 are used by a
`SATPS (GPS) receiver. The code-tracking loop tracks the
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`C/A-code and/or P(Y)-code pulse trains to obtain the signal
`travel time for each relevant satellite.
`The phase-lock loop tracks the satellite's carrier wave
`phase to obtain its carrier phase. Code-tracking allows the
`receiver to measure the appropriate pseudoranges to at least
`four satellites necessary for accurate positioning solutions.
`Carrier phase tracking allows the receiver to measure the
`corresponding carrier phase so the receiver can estimate
`more accurate values for the receiver's pseudorange and the
`three mutually orthogonal velocity components.
`In general, GPS receivers can be either one of two types,
`authorized or unauthorized. The authorized GPS receivers
`are able to receive and decode a second carrier channel L2
`from the orbiting GPS satellites that carries precision code
`(POY)-code) data which must be decrypted with a special
`military decryption device. When selective availability (SA)
`is engaged by the government, the position accuracy of
`unauthorized GPS receivers is degraded because such
`receivers are able to only use the coarse acquisition (CIA)
`code available on the primary carrier channel (L1), and that
`data is deliberately dithered during SA. Position solutions
`which are computed therefore become randomly skewed
`over time in heading and distance from the perfect solution.
`In the preferred embodiment, the GPS-map speed match
`ing vehicle system includes two computers, a GPS computer
`47 and an engine computer 15. The GPS computer includes
`a GPS microprocessor 52, a GPS memory unit 50 with a port
`for data downloading 48, and an input/output bus 46. The
`engine computer 15 comprises a vehicle engine micropro
`cessor 18 and an engine computer memory 16.
`The GPS computer 47 uses the pseudorange and the
`carrier phase measurements to determine the instantaneous
`position coordinates and the instantaneous velocity compo
`nents of the GPS receiver. The GPS memory unit 50
`provides erasable storage for the various Pipes of compu
`tations. Each time used to obtain the first estimates of
`position and to determine which four satellites are most
`favorably positioned for accurate navigation.
`The GPS receiver-computer can be a conventional instru
`ment which is commercially available, e.g., the SCOUT
`marketed by Trimble Navigation (Sunnyvale, Calif.).
`40
`A local database processing facility 42 illustrated in FIG.
`1 receives the latitude, longitude, bearing information and
`speed from GPS microprocessor 52 and uses that data to
`index a plurality of databases, e.g., street, landmark, inter
`section and jurisdiction databases. For instance, the street
`name, block address, city, zip code and jurisdictional infor
`mation are related to latitude and longitude information for
`every significant street in an operational region. Streets are
`also arranged in a hierarchy, such as freeways, highways,
`side streets and alleyways.
`Street intersections are also database related to their
`respective latitudes and longitudes. Street bearings, e.g.,
`north-south, are also stored to provide a bearing constraint
`to improve navigation solution accuracies.
`FIG. 3 depicts a functional diagram of a database pro
`cessing facility 42. Latitude, longitude, bearing and speed
`information 81 from the GPS microprocessor 52 are pro
`vided to the computer indexer 82. The function of the
`database processing facility 80 is to convert latitude and
`longitude data to street address format with the maximum
`posted speed, e.g. "509 Civic Drive, Concord, Calif., maxi
`mum speed is 45 miles/hour', or "Eastbound on 509 Civic
`Drive, Concord, Calif., maximum speed is 45 miles/hour',
`if bearing information is included.
`A plurality of discrete databases, represented by land
`marks database 84, street hierarchy database 85, street
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`segment database 86, speed limit database 87, intersection
`database 88, and jurisdiction database 90, are selectively
`accessed by indexer 82. Indexer 82 may be implemented
`with a personal computer system having a disk operating
`system (DOS) and one or more hard disk drives for storage
`of the databases 84–90. In another embodiment, a plurality
`of CD-ROMs may be used for storage of databases 84-90.
`In yet one more embodiment the local database processing
`facility 42 may be implemented by using GPS memory unit
`50 and GPS microprocessor 52. Commercial hardware and
`software, including relational database software and street
`map information in digital form, are readily available and
`conventional. For instance, ETAK sells the speed limit data
`on a map database.
`Database 85 is a street hierarchy database wherein the
`latitudes and longitudes of various continuous streets within
`a region are related to classes of streets, e.g., by size, such
`as freeway, highway, side street or alleyway. Latitude,
`longitude and bearing information provided in real-time are
`used relational to obtain the name of a street at an appro
`priate classification level.
`Database 86 is a street segment database wherein the
`latitudes and longitudes of various continuous streets within
`a region are relational related to street names, block
`addresses and bearings.
`Database 88 is a street intersection database that includes
`relational data for each intersection of a street with another
`street in a regional geographic area and the earth navigation
`locations of such intersection and the corresponding com
`O Street nameS.
`Database 84 is a landmarks database that includes rela
`tional data for each landmark in a regional geographic area
`and the earth navigation locations of such landmarks and
`their corresponding common street addresses or common
`location descriptors. Examples of such landmarks are the
`Stanford University, the Golden Gate Park, Mount Diablo,
`etC.
`Many other specialized databases can be included in the
`database processing facility 80 for use in a particular appli
`cation. For example, a jurisdictional database 90 can be
`included for reporting the unreasonable speed of the vehicle
`to the local police. Differential correction information can be
`also stored in database processing facility 42 and used to
`correct the position fixes received. This then permits meter
`level position determination accuracies, as may be required
`to settle jurisdictional ambiguities.
`After the location of the vehicle is determined, the com
`puter indexer