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| Method and apparatus for acquiring satellite positioning system signals |
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| OF THE PREFERRED EMBODIMENTS I. Signal Detector Overview A block diagram of one embodiment of a ... |
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Method and apparatus for determining the location of an object which may have an obstructed view of the sky
| Details |
Inventors: Krasner, Norman F.;
Assignee: SnapTrack, Inc. (San Jose, CA)
Primary Examiner: Tarcza; Thomas H.
Assistant Examiner: Phan; Dao L.
Attorney, Agent or Firm: Blakely, Sokoloff, Taylor & Zafman
A positioning sensor receives and stores a predetermined record length of positioning signals while in a fix position located such that the positioning sensor can receive positioning signals. Thereafter, the stored positioning signals are processed to determine the geographic location of the fix position. The fix position may correspond to a location of an object of interest or it may be in a known location relative to the position of the object, in which case once the geographic location of the fix position has been computed, the geographic location of the object can be derived. The positioning sensor includes a Snapshot GPS receiver which may collect and process GPS signals transmitted by GPS satellites using fast convolution operations to compute pseudoranges from the GPS satellites to the fix position. Alternatively, these computations may be performed at a basestation. The computed pseudoranges may then used to determine the geographic location of the fix position. The positioning sensor may be equipped with depth sensing means, such as a pressure sensor, which allows a determination of the depth of submerged object to be made. The positioning sensor may further be equipped with signal detecting means for determining when the positioning sensor is in the fix position. |
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DETAILED DESCRIPTION This invention concerns apparatus and methods for computing the location of a submerged or other remote object which may have an obstructed view of the sky using a global positioning system (GPS) receiver with very low received signal levels.
As illustrated in FIG.
1A, a positioning sensor 10 has first circuitry for receiving and processing pseudorandom sequences transmitted by a number of GPS satellites.
The first circuitry is configured as a Snapshot GPS receiver 12 and is capable of processing the received pseudorandom sequences to determine pseudoranges from the Snapshot GPS receiver 12 to the GPS satellites.
The positioning sensor 10 also includes second circuitry coupled to the Snapshot GPS receiver 12.
The second circuitry is configured to detect a signal which indicates that Snapshot GPS receiver 12 should take a "fix".
That is, the signal indicates that Snapshot GPS receiver 12 should activate its circuitry to receive and store GPS signals transmitted by GPS satellites in the manner described in detail below.
Accordingly, the second circuitry is labeled as signal detector 14.
As shown, signal detector 14 and Snapshot GPS receiver 12 may share a common antenna 16.
In other embodiments, such as that illustrated in FIG.
1B, signal detector 14 and Snapshot GPS receiver 12 may have separate antennas.
In yet other embodiments, for example as shown in FIG.
1D, where signal detector 14 is configured to respond to non-RF signals (e.
g.
, pressure signals, light intensity signals, etc.
), signal detector 14 will use an appropriate sensor 15 (e.
g.
, a pressure sensor, a light sensor, etc.
) in place of an antenna.
Positioning sensor 10 may also be equipped with depth sensor 18 Depth sensor 18 is coupled to Snapshot GPS receiver 12 and is configured to provide information concerning the depth of positioning sensor 10 when positioning sensor 10 is used to locate submerged objects.
Depth sensor 18 may be a pressure sensor and may be the same sensor as signal detector 14 in some embodiments, as illustrated in FIG
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Cell Phones 
