Abstract: An integrated geographic information and automatic position locating system. In one embodiment, a communication link is provided between a vehicle and at least one base station. A vehicle position tracking system, coupled to a vehicle to be monitored, is connected to the communication link. Likewise, a geographic mapping system also disposed within the vehicle is connected to the communication link. In the present embodiment, the vehicle position tracking system and the geographic mapping system are housed in a portable data terminal. The portable data terminal is removably placed into a docking station located within the vehicle. The integrated vehicle position tracking system and geographic mapping system function both when placed in the docking station, and when removed from the docking station. Thus, the present invention provides a mobile integrated vehicle position tracking system and the geographic mapping system integrated into a portable data terminal.

Abstract: Method and apparatus for compensating for the differences in time varying signals S(t;R;S) received and processed by two signal receivers (R.sub.2 and R.sub.3), located at the same site, from two signal sources (S.sub.2 and S.sub.3) that are spaced apart from the receivers. A receiver (R.sub.1) is chosen as a baseline, and two double difference signals DD(t;R.sub.1 ;R.sub.2 ;S.sub.2 ;S.sub.3)=S(t;R.sub.1 ;S.sub.2)-S(t;R.sub.1 ;S.sub.3)-S(t;R.sub.2 ;S.sub.2)+S(t;R.sub.2 ;S.sub.3) and DD(t;R.sub.1 ;R.sub.3 ;S.sub.2 ;S.sub.3)=S(t;R.sub.1 ;S.sub.2)-S(t;R.sub.1 ;S.sub.3)-S(t;R.sub.3 ;S.sub.2)+S(t;R.sub.3 ;S.sub.3) are formed. Time averages of these two double difference signals are formed, using a time interval of length T lying in a preferred range, and are subtracted from the corresponding double difference signals to form first and second compensated signals.

Abstract: A system embodiment of the present invention comprises a fixed and a roving pair of four-observable GPS receivers and a communication link between them for double differencing code and carrier measurements. Carrier phase integer ambiguities are resolved efficiently by searching the simultaneous narrow-lane intersections of both the L1 and L2 wave fronts propagated by the GPS satellites being tracked. External constraint information, such as elevation, is additionally used to speed up integer ambiguity resolution. Data between the reference station and the rover is communicated in compressed form at a regular interval, e.g., once a second at each epoch, and demi-measurements of carrier phase are obtained more frequently, e.g., ten times a second, and used to propagate solutions between epochs.

Abstract: Methods for authentication or validation of the location of a putative source (ps) of a message, using time varying location determination (LD) signals that are received from J sources (J>1) of LD signals G(t;j;ps) that are spaced apart from the putative source. The putative source forms an augmented data signal that includes the original message, one or more segments g?t.sub.k(m),t.sub.k(m+1) ; j; ps!={G(t.sub.r ;j;ps).vertline.t.sub.k(m) .ltoreq.t.sub.r .ltoreq.t.sub.k(m+1) } of the LD signals for a selected time interval, a putative source asserted location L(t".sub.k(m) ;ps) for a time t".sub.k(m) in the selected time interval, and other identifying parameters. The augmented data signal is received by a central station that analyzes the LD signal segments and determines whether the asserted location L(t".sub.k(m) ;ps) is likely to be the true message source location. Part or all of the augmented data signal can be encrypted for transmission.

Abstract: A route exception reporting apparatus is mounted in a mobile shipping vehicle having a predetermined geographic route. The shipping vehicle may be a self-propelled vehicle containing cargo or may also be a separable self-contained shipping container carried on a transportation vehicle. At least a portion of the predetermined route is stored in the apparatus on board the shipping vehicle. The apparatus is provided with a geographic locating means for determining the shipping vehicle location, a comparator means for comparing the shipping vehicle location with at least one point of the predetermined route and a communication means for communicating with a central station. The apparatus is configured to communicate the shipping vehicle location to the central station when the comparator means computes a difference between the shipping vehicle location at a particular point in time and the predetermined route point corresponding with that particular time point which exceeds a predetermined limit.

Abstract: A real-time kinematic system includes base and rover GPS units connected by a data link. The rover unit is typically moved to points of interest during a survey while the base remains over a fixed, and known location. An initialization testing program of the present invention is mounted on a personal computer platform that forces in the rover a loss of signal tracking, thus simulating losses in signal reception caused by obstructions of the satellite signals. A complete initialization is forced to occur. The test program uninitializes the RTK solution by causing a loss of integer ambiguities resolution by forcing a loss of lock on one or more satellites. The test program then monitors the subsequent initialization process, e.g.

Abstract: A GPS timing receiver for providing a GPS-derived time signal. The GPS timing receiver includes a filter for filtering a GPS signal to a certain information bandwidth, a reference clock for generating a reference clock signal having a clock rate at least ten times the information bandwidth, a sampler using the reference clock signal for oversampling the filtered GPS signal, a correlation subsystem including a microprocessor for correlating the sampled GPS signal to the reference clock signal to measure a time difference between the GPS signal and the reference clock signal, and a time clock to issue a GPS-derived time signal based upon the reference clock signal and adjusted by the measured time difference in increments of the period of the reference clock signal. An optional frequency multiplier multiplies the reference clock rate enabling the time clock to adjust the GPS-derived time signal in increments of the period of the frequency multiplied reference clock signal.

Abstract: An apparatus and a method for transmitting and receiving a signal having multiple tones for obviating destructive interference between a groundwave and a skywave of the signal. The multiple tones have a frequency offset that is calculated so that the destructive interference nulls for each of the tones occurs at different range distances from the transmitter thereby extending the distance over which at least one of the tones can be reliably received.

Abstract: A system, method, and apparatus for displaying map information in a cardinal direction-up setting. In one embodiment, map information is displayed on a display terminal. Next, an icon representing the position and heading of an item with respect to the displayed map information is placed over the displayed map information. In the present invention, the map information is displayed in a cardinal direction-up setting corresponding to the heading of the icon. Thus, if the heading of the icon is directed in a substantially eastern direction, the map information is displayed in an east-up orientation. The present invention further includes hysteresis logic which regulates when a different cardinal direction is oriented upward.

Abstract: The personal tracking system including the intelligent position determining means coupled with the cellular phone and the base station is disclosed. The base station includes a computer, a modem, and a telephone. The computer further includes base station software for communicating with the mobile unit. The mobile unit transmits the location data to the base station at certain times and at certain locations.

Abstract: A method for accurately determining the location of a pre-selected survey or construction mark, or for accurately identifying the survey position for a new mark with pre-selected location coordinates. A Satellite Positioning System (SPS), such as GPS or GLONASS, with at least two SPS stations (antennas and receiver/processors) is used to receive and analyze SPS signals from four or more SPS signal satellites. An SPS signal reference station is placed at a position with known location coordinates, which can be stationary or be known functions of time. An SPS signal roving station receives the location coordinates of the reference station and determines its own location coordinates relative to the reference station, using SPS differential positioning. The roving station is then moved to a pre-selected survey mark or position, either to locate that survey mark or to identify (by marking) a new survey position from pre-selected location coordinates.

Abstract: A system and method for positioning control and management of racing sailboat positions and velocities includes the strategic placement of global positioning receivers and transmitters at a buoy and committee boat marking the sail race start line, as well as radio and global positioning receivers on the sailboat. Global positioning system (GPS) and radio transmitter units are mounted on a race start buoy and committee boat and another GPS and radio transceiver unit receives GPS signals from positioning satellites and radio signals from the race start buoy and committee boat. The information received by the racing sailboat is processed to determine relative and absolute positions and velocities, and estimated time of arrival (ETA) at the intercept between current sailboat course and the race start line for display in user-friendly race management.

Abstract: A method for compensating for temporary loss of differential GPS correction signals for a satellite, numbered j, during an IODE changeover interval. Differences .DELTA.e.sub.i (t;j;n+1,n)=e.sub.i (t;j;n+1)-e.sub.i (t;j;n) (i=1, . . . , I) are formed for I ephemeris parameters used to describe the ephemeris for the satellite (j) during IODE intervals number n+1 and n. These differences are approximated for a DGPS blank-out time interval, given by t(j;n+1).sub.IODE .DELTA.t.sub.rev,mob .ltoreq.t<t(j;n+1).sub.IODE +.DELTA.t.sub.ch +.DELTA.t.sub.rev,ref, during which a GPS reference station continues to broadcast DGPS correction information based on the old ephemeris data that was valid during the preceding IODE time interval, given by t(j;n).sub.IODE .ltoreq.t<t(j;n+1).sub.IODE. These ephemeris differences are used by a mobile station that receives DGPS correction information from the GPS reference station to produce corrected GPS information for a blank-out time interval.

Abstract: A new and useful method and apparatus are provided for collecting, recording and displaying data pertaining to artifacts in a time based fashion. The apparatus includes a data measurement device such as a GPS receiver or other measurement device for collecting data such as position information pertaining to artifacts, a memory for recording collected data and a user interface having an input for receiving recorded information such as qualitative information pertaining to artifacts from the user and a display for displaying the collected data as it is collected by a user. The user interface includes a time scale to associate the data collected pertaining to the artifacts with the time at which the data was collected providing a useful project management tool for the user as well as for management personnel supervising the user and for providing an accurate time based archival record of data pertaining to artifacts such as their location and physical condition.

Abstract: A method for characterization of data measurements made on signals received from a plurality of SATPS satellites that facilitates post-processing of these data to determine pseudoranges, code phases, carrier phases, pseudorange rate corrections, carrier phase corrections, spatial location, velocity and time coordinates and other variables of interest for an SATPS user. The SATS may be any satellite-based location determination system, such as GPS or GLONASS. The approach uses six indices h1, h2, h3, h4, h5 and h6, with the first index h1 including the total solution coordinates (t.sub.n,x.sub.n,y.sub.n,z.sub.n) for the location fix time t=t.sub.n at which measurements are made, and the spatial location and velocity coordinates. The second and third indices h2 and h3 specify the in-view satellite constellation that provided the SATPS signals and the IODC parameter.

Abstract: A navigation satellite receiver for demodulating spread spectrum transmissions on pairs of L-band microwave carrier frequency channels, L1 and L2, which use the same pseudorandom number spreading code. A single P(Y)-code generator is used to produce independent P(Y)-code outputs for L1 and L2. The relative P(Y)-code phase between the outputs is adjusted by a phase resolver to account for the dissimilar delays the ionosphere imposes on each of L1 and L2. The phase resolver counts the excess of L1 code clocks over the L2 code clocks with a digital counter and adjusts a digital delay line to compensate.

Abstract: An improved navigation satellite receiver for tracking individual spread-spectrum frequency spectral lines with a microwave receiver antenna to receive signals from orbiting navigation satellites, a downconverter to produce in-phase and quadrature (I and Q) signals from the received satellite signals, and a digital processing system for frequency and phase locking numeric controlled oscillators (NCO) to the carrier and code of the satellite signals. The improvement comprises at least one spectral line tracker connected to receive the (I and Q) signals and including a spectral line numeric controlled oscillator (NCO) connected to a spectral line mixer that drives a spectral line code correlator. The spectral line NCO is frequency-aided to frequency lock on a spectral line from a value obtained from the carrier NCO.

Abstract: A tape measurement apparatus is provided for measuring the slope height of a GPS surveying system receiver, with an integral antenna, which is vertically suspended over a ground mark. A tape mounting hook is provided for securing the distal end of a tape measure in a location which is known precisely with respect to the phase center of the GPS receiver. The tape measure housing has a pointer arm of precisely known length which extends out from the tape measure housing in a direction opposite and parallel to the normalized line of extension of the tape from the housing. A distance scale imprinted on the tape compensates for the combined lengths of the housing and pointer arm so that a user can read the uncorrected slope height of the GPS receiver directly from the scale while applying the tip of the pointer arm to the ground mark.

Abstract: A dual frequency vertical antenna for radiating a first and a second airwave signal in response to a first and a second conducted signal, the first airwave signal having a first frequency and the second airwave signal having a second frequency lower than one-half the first frequency. The antenna includes a horizontal base member and a vertical mast, including a coaxially disposed rod, projecting upward from the base member to a masthead. For feeding the conducted signals, a lower mast extension projecting downward from the base member and a tuning sleeve projecting either upward or downward from the base member are tuned to 1/4 wavelength at the first frequency and a single coaxial cable is connected between the base member and a feedpoint on the rod. The first airwave signal radiates from a dipole formed of an 1/4 wavelength upper rod extension extending upward from said masthead and a concentric 1/4 wavelength upper sleeve external to the mast projecting downward from said masthead.

Abstract: The method and apparatus for observing unknown codes on the Satellite Positioning System satellites are disclosed. The technique employs the parabolic high gain antenna to determine the energy spectrum of the unknown W code. The technique does not provide sufficient accuracy to implement the effective anti-spoofing device.