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: An adjustment mechanism for a telescope of a theodolite. The mechanism includes a worm gear that is coupled to a friction gear of the theodolite. The friction gear is coupled to the telescope so that any rotation of the gear will induce a corresponding movement of the scope. The worm gear is coupled to a linear screw and an outer sleeve. The linear screw has a shaft that can push the worm gear and rotate the friction gear to provide a fine movement of the telescope. The linear screw also has a stop that engages an arm of the sleeve. Continued rotation of the linear screw rotates the engaged sleeve and the worm gear to provide a coarse movement of the telescope. The linear screw is connected to a knob which can be rotated by an operator. The operator can induce a coarse movement of the telescope by turning the linear screw so that the stop engages the sleeve.

Abstract: A half-dead reckoning satellite navigation receiver comprises a receiver for tracking and acquisition of two, three, four or more satellites and for computing navigation solutions from the available satellites. A navigation computer is included that provides for navigation when only three satellites are visible by constraining the altitude. The navigation computer further provides for a half-dead-reckoning mode of operation when only two satellites are visible and the altitude is constrained by providing a one dimensional satellite navigation solution. The receiver position is projected by dead reckoning with the projection corrected in one axis only that is perpendicular to the available horizontal line of position.

Abstract: A three dimensional structure is precisely positioned at a desired location. A virtual model of the structure of interest is created and stored in a computer memory. Some time later, remote sensors are placed in selected positions on the structure of interest. The sensors are configured so as to provide real time location, attitude and orientation information regarding the structure and may consist of GPS remote units, tilt meters, gyro compasses, and pressure sensors. The position of each the remote sensors on the actual structure is also recorded in the computer memory so that the virtual model accurately reflects the configuration of the structure. As the structure is being positioned, the real-time location, attitude and orientation information produced by the remote sensors is monitored at a base station and used to update the virtual model. In this way, the virtual model accurately reflects the current location, attitude and orientation of the structure.

Abstract: Measurement corrections transmitted from reference stations at known positions are transmitted to differential Global Position System receivers for use in computation of position information relative to the receiver. In one embodiment, circuitry included in the receiver detects errors in transmissions of measurement correction data streams from the closest reference station and replaces erroneous portions of the data streams with corresponding portions received from a second reference station. Alternately, a plurality of measurement correction data streams received from a plurality of reference stations are combined to produce a combined measurement correction used to correct the position information received from satellites.

Abstract: A message system, global positioning system (GPS) receiver apparatus, and method for providing a fast time to first location fix and a low average power consumption in a GPS receiver. The message system includes a GPS base station for receiving a GPS signal and providing GPS acquisition and location information including GPS satellite visibility, health, and ephemeris; and a message system manager for transmitting a radio message signal including a wakeup call and the GPS information. A message transceiver or receiver receives the radio message signal and passes the wakeup call and GPS information to a GPS receiver having a low power standby mode. The GPS receiver awakens from the standby mode and enters an operational mode for using the GPS information for acquiring the GPS signal and deriving the first location fix. In a first embodiment, the GPS receiver initiates the first fix by requesting the message transceiver to transmit a radio request signal.

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: The r.f. power generating apparatus interacting with the communication network is disclosed. The apparatus comprises the dummy load and the computer operated antenna-dummy load switch. The computer operates the antenna-dummy load switch in such a way that the attack and decay phases associated with the data transmission from the r.f. power generating apparatus to the communication network are eliminated. A plurality of the r.f. apparatuses interacting with the same communication network on the same frequency wherein each of the apparatuses includes the antenna-dummy load switch is also disclosed.

Abstract: The present invention comprises a Global Positioning System (GPS) Wide Area Augmentation System (WAAS) retrofit receiver. In one embodiment the present invention includes a receiver adapted to receive WAAS messages via an antenna. The receiver is further adapted to translate the WAAS messages into RTCM SC-104 standard messages and transmit the messages to an external GPS receiver via a communications link. In so doing, the external GPS receiver is able to utilize the WAAS messages without modification of the external GPS receiver.

Abstract: A compact combined position locating and analog cellular telephone unit. A single processor is coupled to a position locating system and a cellular telephone system. In the present invention, the single processor controls the functions and operation of both the position locating system and the cellular telephone system. In one embodiment, the position locating system, the cellular telephone system and the single processor are all disposed on a single substrate.

Abstract: A frequency synthesizer comprises a voltage controlled oscillator (VCO) with an output frequency f.sub.out that is dependent on a VCO-control voltage input. A divide-by-k counter is connected to receive the output frequency f.sub.out and to output a pair of in-phase and quadrature phase signals f.sub.k. A vector modulator is connected to receive the in-phase and quadrature phase signals f.sub.k and the output frequency f.sub.out, and outputs a single sideband (SSB) modulated output f.sub.n comprising only one of the sum (f.sub.out +f.sub.k) or difference (f.sub.out -f.sub.k) products. A divide-by-n counter is connected to receive the modulated output f.sub.n and to output a feedback frequency sample f.sub.f. And a phase detector is connected to receive the feedback frequency sample f.sub.f and to compare it with a reference frequency f.sub.r. A phase error output signal is provided for the VCO-control voltage input.

Abstract: A guidance system for movable machinery comprising a GPS processor unit in a "gorilla box" connected to a shock mounted and protected GPS antenna and an operator display with a lightbar that indicates to an operator of the machinery to steer up/down or left/right.

Abstract: Apparatus for determining the present location of an observer on the Earth's surface, the apparatus including an antenna to receive Global Positioning System (GPS) signals from two or more GPS satellites and a credit card size GPS signal processing Smartcard attached to the antenna that receives the GPS signals and determines and displays the present position of the antenna. In one embodiment, the signal processing card includes a frequency downconverter to downconvert the frequency of the GPS signals received, a digital signal processor and associated memory device that is programmed to determine the present antenna location from the GPS signals received, and an information transfer device linked to a nearby host computer or other electronic device for further data processing and display. In other embodiments, the antenna, or the antenna and the downconverter, are contained on a separate card.

Abstract: Methods for synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, which consists of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal. An idealized correlation function A.sub.I (t), formed from the product of a digital reference signal with a time-shifted reference signal, and a measured correlation signal A.sub.M (t), formed from the product of a received signal and a time-shifted reference signal, are computed. Peak amplitudes A.sub.M (.sub.pM) and A.sub.I (.sub.pI) are found for the respective measurable and idealized punctual code phase shifts .sub.pM and .sub.pI. The correlation measurements formed on the early side (or on the late side) of the peak for the correlation function A(t) are combined to form an estimate of the time delay associated with a multipath signal.

Abstract: A GPS receiver and a method for improving time to first fix (TTFF). The GPS receiver includes an internal clock for maintaining an approximate clock time during a standby mode and a microprocessor system including a data bit timer code, a temperature compensation code, and a learned time adjustment code. When the GPS receiver enters an operational mode, the data bit timer code instructs the microprocessor system for determining a GPS-based clock time by aligning the approximate clock time according to a time-of-arrival of a GPS data bit when the approximate clock time and the GPS-based clock time are estimated to be within a correction range of ten milliseconds. The temperature compensation code and a learned time adjustment code include instructions for using a stored frequency/temperature characteristic and a learned time correction, respectively, for estimating and compensating for time drift that has occurred during the standby mode.

Abstract: A motorized rack system for loading and unloading long items such as ladders includes a static rack for holding one end of a ladder and a pivoting and extendible rack. The extendible ladder rack assembly includes a base member mounted to the roof of a vehicle, an elongated pivoting member, and a slideable ladder carriage member. The system also includes a mechanism for positioning the pivotable and extendible ladder rack assembly in a first locked down position of the ladder rack, a second tilted position, and a third tilted/extended position for loading and unloading a ladder. A cable is coupled to the one end of the pivoting member and a cable-spooling mechanism pays out and reels in the cable for positioning the motorized ladder rack.

Abstract: A data message formatting program, method and system uses a script-driven, Output Description Language (ODL) program module. The ODL module interprets and executes instructions from an ASCII .ODL script file. The .ODL instructions and the ODL programming language cooperate with the output of a conventional data entry and display program module. The close coupling of the data structures of the data entry module and the ODL module provide a powerful means for automatically re-formatting data entered prior to transmission over a communication network. The .ODL file may be generated by a system administrator or user with a conventional text editor by following an Output Description Language Programming manual. The .ODL file and ODL module are designed to be used in combination with a Form Interpretive module (FIM) and corresponding form data file which are also installed on the system.

Abstract: Method and apparatus for determining the attitude or angular orientation of a moving vehicle or other moving body, using either two spaced apart antennas or a single antenna attached to or connected with the vehicle. Where two antennas are used, the spatial locations of each antenna are determined at a first selected time, and the spatial location of one antenna is determined at a second selected time. These three spatial locations determine a plane whose normal vector allows determination of the vehicle attitude at a time determined by the first and/or second selected times. Four or more spatial locations can also be used to determine a plane that indicates vehicle attitude. Where one antenna is used, for example, in a vehicle turn, the antenna spatial locations at three distinct selected times determine a plane that allows determination of the vehicle attitude at a time determined to the first, second and/or third selected times.

Abstract: A carrier ambiguity detector for resolving a 1/2 cycle carrier phase ambiguity in an incoming GPS signal before the arrival of the next preamble by detecting a match or an inverted match between an internally stored expected data message and the incoming data in the remaining subframe before the arrival of the next preamble. The carrier ambiguity detector of the present invention includes a buffer for buffering incoming data, a data memory for storing time-tagged expected data, a data pointer for selecting certain expected data corresponding to a GPS-based time that is synchronized to the incoming data, non-inverting and inverting comparators for comparing the buffered data to the expected data, and a data compare detector coupled to the comparators for indicating a non-inverted or an inverted match for a zero degree or a one-hundred eighty degree resolution, respectively, of carrier phase information.

Abstract: A Global Positioning System (GPS) receiving apparatus that is powered by a control or data interface signal from a computing apparatus. The GPS receiving apparatus includes a GPS receiver for receiving GPS satellite signals and providing GPS-derived location information and a converter for converting the interface signal to operating power signal for operating the GPS receiver. Optionally, the GPS receiver includes a power controller for controlling a duty cycle of the operating power in the GPS receiver in order to not exceed the power available from the interface signal. The interface signal is transmitted according to an interface standard such as RS232, RS422, or PC parallel.