US 4,809,005 AGranted

Multi-antenna gas receiver for seismic survey vessels

AssigneeWestern Atlas International, Inc.

InventorCharles C. Counselman, III

Life of this patent

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Abstract

Method and apparatus are disclosed for accurately determining position from GPS satellites and received on a ship using observations of C/A code group delay, L1 band center frequency carrier phase, L1 band 5.115 MHz implicit carrier phase, and L2 band 5.115 MHz implicit carrier phase. A precise measurement of the range to each satellite is made based upon the L1 center frequency carrier phase. A correction for ionospheric effects is determined by simultaneous observation of the group delays of the wide bandwidth P code modulations in both the L1 and L2 bands. These group delays are determined by measuring the phases of carrier waves implicit in the spread-spectrum signals received in both bands. These carriers are reconstructed from both the L1 and L2 band signals from each satellite without using knowledge of the P code. The unknown biases in the L1 center frequency carrier phase range measurements are determined from simultaneous, pseudorange measurements, with time averaging. The instantaneous position of the antenna receiving these signals, and therefore the ship, may then be determined from the ranges so determined, with both the bias and the ionospheric effects having been eliminated. Additional antennas are positioned on the ship and a seismic streamer towed by the ship to reject false signals, compensate for blockage of signals by the ship's structure, and determine the position of sensors in the streamer.

Claims9

Dependent claims

A method of determining ship towed sensor position information from code modulated, overlapping spread spectrum signals transmitted by a plurality of GPS satellites and modulated by satellite specific codes, comprising the steps of:

receiving a first composite of satellite signals related to ship position;
forming identical, synchronous, digital representations of the composite in a plurality of satellite tracking channels;
developing estimates in each tracking channel of group delay and phase delay, with respect to a common time base, of a satellite specific, code modulated component of the composite;
detecting a component in each channel by logical combination of the composite representation with a model of the component generated synchronously from the common time base in accordance with the estimates;
updating the estimates in accordance with the detected components to form time series of phase and group delay observations for each channel;
receiving a second composite of satellite signals related to sensor position;
forming a digital representations of the second composite;
developing an estimate of delay, with respect to the common time base, of a satellite specific, code modulated components of the second composite;
detecting said component by logical combination of the second composite representations with a model of the component generated synchronously from the common time base in accordance with the related estimate;
updating the estimate in accordance with the detected component to form time series of observations related to the second composite;
and
processing the observations to determine sensor position.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/147,123Filed 21 Jan 1988 · continuation
Priority: 1 Mar 1982
Granted: 28 Feb 1989
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

G01S 19/04
Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers: providing…
G01C 15/00
Surveying instruments or accessories not provided for in groups g01c1/00 - g01c13/00
G01S 19/32
Receivers: multimode operation in a single same satellite system, e.g. GPS L1/L2
G01S 19/35
Receivers: constructional details or hardware or software details of the signal processing chain