# US 2013/0155808 A1 · Method and Device for Estimating an Inter-node Distance Between Nodes Arranged Along Towed Acoustic Linear Antennas > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0155808 A1 - Document ID: US20130155808A1 - Status: Published application - Kind: A1 - Application number: 13/720,398 - Filed: 2012-12-19 - Published: 2013-06-20 - Earliest claimed: 2011-12-19 - Assignees: Sercel - Inventors: Christophe L'Her; Simon Vallez - Web page: https://patentgrep.com/patent/US20130155808A1 ## CPC - G01V 1/38: specially adapted for water-covered areas (G01V1/28 takes precedence) - G01S 11/14: using ultrasonic, sonic or infrasonic waves - G01V 1/3808: {Seismic data acquisition, e.g. survey design} - G01S 1/72: using ultrasonic, sonic or infrasonic waves - G01V 1/3835: {measuring position, e.g. by GPS or acoustically} - G01V 1/3861: {control of source arrays, e.g. for far field control} - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES ## Abstract A method and apparatus are provided for estimating an inter-node distance between a sender node and a receiver node belonging to a network comprising a plurality of nodes arranged along towed acoustic linear antennas. An acoustic signal is transmitted from the sender node to the receiver node through an underwater acoustic channel. The method includes estimating the inter-node distance as a function of an estimate of a sound speed profile of the underwater acoustic channel, the sound speed profile depending on depth. ## Claims ### Claim 1 A method comprising: estimating an inter-node distance between a sender node and a receiver node belonging to a network comprising a plurality of nodes arranged along towed acoustic linear antennas, an acoustic signal being transmitted from the sender node to the receiver node through an underwater acoustic channel, wherein estimating comprises: estimating the inter-node distance as a function of an estimate of a sound speed profile of the underwater acoustic channel, said sound speed profile depending on depth. ### Claim 2 (depends on 1) The method according to claim 1, wherein said step of estimating the inter-node distance comprises steps of: obtaining a travel time of the acoustic signal from the sender node to the receiver node, immersion depths of the sender node and the receiver node, a sound speed at the immersion depth of the sender node and said estimate of the sound speed profile; determining an approximated inter-node distance, corresponding to a straight line path between the sender node and the receiver node, as a function of the travel time and the sound speed at the immersion depth of the sender node; estimating the sound propagation between the sender node and the receiver node, using a sound propagation model and knowing the immersion depths of the sender node and the receiver node, the approximated inter-node distance and the estimate of the sound speed profile, said step of estimating the sound propagation providing an arc length of an arc path between the sender node and the receiver node; and determining an estimate of the inter-node distance, as the difference between said approximated inter-node distance and a distance estimation error defined as the difference between said arc length and said approximated inter-node distance. ### Claim 3 (depends on 2) The method according to claim 2, wherein the step of obtaining the estimate of the sound speed profile is carried out using at least one method belonging to the group consisting of: methods of consulting at least one sound speed profiles database; or methods of direct measuring, using a measurement device and/or an acoustic method. ### Claim 4 (depends on 2) The method according to claim 2, wherein the step of obtaining the estimate of the sound speed profile is carried out with a method of indirect measuring, using an inversion process which extracts the estimate of the sound speed profile from at least one distorted acoustic signal resulting from the transmission of an acoustic signal between a couple of nodes through said underwater acoustic channel. ### Claim 5 (depends on 4) The method according to claim 4, wherein said inversion process extracts the estimate of the sound speed profile from a distorted acoustic signal resulting from the transmission of said acoustic signal between said sender node and said receiver node through said underwater acoustic channel. ### Claim 6 (depends on 4) The method according to claim 4, wherein at least two iterations of said inversion process are executed exploiting a spatial diversity, using at least two different couples of nodes, and/or a time diversity, using a same couple of nodes at at least two different instants, each iteration providing an intermediate estimate of the sound speed profile, and wherein the step of obtaining the estimate of the sound speed profile comprises a step of combining the intermediate estimates of the sound speed profile to obtain a final estimate of the sound speed profile. ### Claim 7 (depends on 6) The method according to claim 6, wherein said at least two different couples of nodes have different depths, a first and a second couple of nodes being defined as having different depths if a sender node of the first couple has not the same depth as a sender node of the second couple, and/or if a receiver node of the first couple has not the same depth as a receiver node of the second couple. ### Claim 8 (depends on 1) The method according to claim 1, wherein said step of estimating the inter-node distance comprises a step of using an inversion process which extracts jointly an estimate of the sound speed profile and an estimate of the inter-node distance, from a distorted acoustic signal resulting from the transmission of said acoustic signal between said sender node and said receiver node through said underwater acoustic channel. ### Claim 9 (depends on 1) The method according to claim 1, wherein said step of estimating the inter-node distance comprises steps of: obtaining said estimate of the sound speed profile; and using an inversion process which extracts an estimate of the inter-node distance, from a distorted acoustic signal resulting from the transmission of said acoustic signal between said sender node and said receiver node through said underwater acoustic channel, and knowing said estimate of the sound speed profile. ### Claim 10 (depends on 9) The method according to claim 9, wherein the step of obtaining the estimate of the sound speed profile is carried out using at least one method belonging to the group comprising: methods of consulting at least one sound speed profiles database; and methods of direct measuring, using a measurement device and/or an acoustic method. ### Claim 11 (depends on 8) The method according to claim 8, wherein said step of estimating the inter-node distance comprises steps of: obtaining a travel time of the acoustic signal from the sender node to the receiver node, an immersion depth of the sender node, a sound speed at the immersion depth of the sender node; determining an approximated inter-node distance, corresponding to a straight line path between the sender node and the receiver node, as a function of the travel time and the sound speed at the immersion depth of the sender node; and wherein said inversion process is initialized with said approximated inter-node distance. ### Claim 12 (depends on 1) The method according to claim 1, wherein the method is implemented by said receiver node or a centralized system. ### Claim 13 (canceled) ### Claim 14 A non-transitory computer-readable carrier medium storing a program which, when executed by a computer or a processor, causes the computer or the processor to carry out a method of estimating an inter-node distance between a sender node and a receiver node belonging to a network comprising a plurality of nodes arranged along towed acoustic linear antennas, an acoustic signal being transmitted from the sender node to the receiver node through an underwater acoustic channel, the method comprising estimating with the computer or processor the inter-node distance as a function of an estimate of a sound speed profile of the underwater acoustic channel, said sound speed profile depending on depth. ### Claim 15 A device for estimating an inter-node distance between a sender node and a receiver node belonging to a network comprising a plurality of nodes arranged along towed acoustic linear antennas, an acoustic signal being transmitted from the sender node to the receiver node through an underwater acoustic channel, wherein the device comprises: means for obtaining an estimate of a sound speed profile of the underwater acoustic channel, said sound speed profile depending on depth; and means for estimating the inter-node distance as a function of said estimate of the sound speed profile.