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 Personal Digital Location Apparatus for displaying a geographical location as an icon on a map. The apparatus includes a GPS Smart Antenna for determining the geographical location, a personal computing device including a display, a processing system including a standard software operating system such as DOS, Windows, Macintosh, or Geoworks, and a map application program capable of running in the operating system. The GPS Smart Antenna includes an internal battery and a power sensor for sensing the connection of an external power source. The GPS Smart Antenna receives power from the external power source when the power sensor senses that the external power source is connected and receives power from the internal battery when the power sensor senses that the external power source is not connected.

Abstract: Method and apparatus for determining the present location of a missing vehicle, such as an automobile or marine vessel, using a Global Positioning System that receives GPS signals from two or more GPS satellites. A GPS antenna, GPS signal receiver/processor, a paging responder, a cellular telephone and associated antenna, and a controller/modem are installed in a vehicle and electrically connected together. When the vehicle is determined to be missing, because the vehicle has been misplaced, lost or stolen, the vehicle owner or operator contacts a vehicle location service center, which broadcasts a paging request that is received by the paging responder on the vehicle. The paging responder causes the controller/modem to interrogate the GPS receiver/processor to determine the present location of the vehicle. The receiver/processor determines the present vehicle location and notifies the controller/modem of such location.

Abstract: Apparatus for determining and broadcasting the approximate location of a person or other object that has fallen overboard from a boat or other structure into a body of water. The apparatus includes a floatable object that is thrown into the water near the overboard person/object to broadcast the location of the object and the nearby overboard person. The floatable object includes: an activatable Satellite Positioning System (SPS) receiver/processor and antenna to receive SPS signals from two or more SPS satellites; an activatable location transmitter and transmitter interface to receive the SPS-determined location information from the SPS receiver/processor; a power supply to supply power to the SPS receiver/processor and the location transmitter; and activation means to activate the SPS receiver/processor and location transmitter.

Abstract: An antenna is employed to receive a (1540 f0) L1 GPS-satellite signal. In addition, a filter, an (RF) amplifier, a harmonic mixer, and a (sole) local oscillator are employed, the combination configured to mix the seventh harmonic of a 192 f0 local oscillator generated signal with the receive satellite signal to down-convert the frequency of the received GPS-satellite signal to a 196 f0 IF frequency. Further, another filter, an (IP) amplifier, and a mixer are employed, the combination configured to mix the fundamental of the 192 f0 local oscillator generated signal with the 196 f0 GPS-satellite signal to down-convert the frequency of the satellite signal to four f0. Finally, yet another filter and an amplifier are employed, the combination configured to filter and amplify the four f0 GPS-satellite signal.

Abstract: To reduce error introduced by the local oscillator in the velocity calculations, the receiver has two "tracking channels" and a microcomputer. With numbers required to, simultaneously, lock each of the "tracking channels" each to a respective satellite signal, the microcomputer employs a differential doppler technique to calculate the receiver velocity. The microcomputer calculates a number which represents the difference between the apparent doppler frequency shift of the carrier signal which is transmitted by the first "tracking channel" satellite and which is measured over a specific time period and the apparent doppler frequency shift of the carrier signal which is transmitted by the second "tracking channel" satellite and which is measured over substantially the same time period.

Abstract: Two receiver channels each driven by a common local oscillator signal are employed. The signal developed by the first receiver channel is used to drive in phase (I) and quadrature (Q) counters of a Castas-loop, which phase-locks to the signal. The signal developed by the second receiver channel is used to drive another pair of in phase (I) and quadrature (Q) counters, which develop signals from which heading information is calculated.