US-20260126537-A1 - ACOUSTIC SURVEYING USING SOUND VELOCITY PROFILE CAST FREQUENCY BASED ON A LOCAL SOLAR NOON TIME VALUE

US20260126537A1US 20260126537 A1US20260126537 A1US 20260126537A1US-20260126537-A1

Abstract

Described are systems and techniques for optimizing sound velocity profile (SVP) cast frequency for solar heating effects. Location information associated with a survey vessel or acoustic survey can be obtained and used to determine a time value of local solar noon (LSN) based on the location information. A time interval can be determined corresponding to increased water column heating from solar irradiance, the time interval based on configured offsets from the time value of LSN. A first subset of a plurality of SVP measurements can be obtained outside of the time interval and using a first sampling periodicity that is longer than a second sampling periodicity used to obtain a second subset of the plurality of SVP measurements within the time interval. Unlocking insights from Geo-Data, the present invention further relates to improvements in sustainability and environmental developments: together we create a safe and livable world.

Inventors

Helen Frances Stewart
Jenny Ruiz Tixier
Jeffrey William Croucher
Jarrot Jerome Spurlock

Assignees

FNV IP BV.

Dates

Publication Date: 20260507
Application Date: 20241104

Claims (20)

1 . A method comprising: obtaining location information associated with one or more of a survey vessel or an acoustic survey associated with the survey vessel; determining a time value of solar noon associated with the location information, wherein the time value of solar noon is determined based on the location information; determining a time interval corresponding to increased water column heating from solar irradiance of a water column beneath the survey vessel, wherein the time interval is determined using one or more configured offsets from the time value of solar noon; and performing the acoustic survey to obtain a plurality of sonar measurements and a plurality of sound velocity profile measurements within the water column, wherein: a first subset of the plurality of sound velocity profile measurements is obtained outside of the time interval and using a first sampling periodicity; and a second subset of the plurality of sound velocity profile measurements is obtained within the time interval and using a second sampling periodicity, wherein the second sampling periodicity is shorter than the first sampling periodicity.
2 . The method of claim 1 , further comprising: determining updated location information associated with one or more of the survey vessel or the acoustic survey; determining an updated time value of solar noon based on the updated location information; and updating the time interval using the updated time value of solar noon.
3 . The method of claim 2 , wherein the updated time value of solar noon is determined in response to a difference between the updated location information and the location information being greater than or equal to two degrees of longitude.
4 . The method of claim 1 , wherein the second sampling periodicity is less than or equal to half of the first sampling periodicity.
5 . The method of claim 1 , wherein performing the acoustic survey includes: increasing, in response to a start of the time interval, a quantity of sound velocity profile measurements obtained per hour from a first number to a second number; and decreasing, in response to an end of the time interval, the quantity of sound velocity profile measurements obtained per hour from the second number to the first number, wherein the first number corresponds to the first sampling periodicity, and wherein the second number corresponds to the second sampling periodicity.
6 . The method of claim 1 , wherein: the plurality of sonar measurements are obtained using one or more sonar transceivers coupled to a hull of the survey vessel and positioned within the water column; and the plurality of sound velocity profile measurements are obtained using an underway profiler deployed from the survey vessel into the water column, wherein the underway profiler is deployed corresponding to the first sampling periodicity outside of the time interval and is deployed corresponding to the second sampling periodicity within the time interval.
7 . The method of claim 6 , wherein: the one or more sonar transceivers comprise one or more multibeam echosounder (MBES) transducer arrays; and the underway profiler comprises an underway sound velocity profiler (SVP), preferably a towed SVP.
8 . The method of claim 1 , wherein the location information is indicative of at least a longitude of a geographic location corresponding to one or more of the survey vessel or the acoustic survey, and wherein the time value of solar noon corresponds to the longitude.
9 . The method of claim 8 , wherein the time value of solar noon further corresponds to one or more of a latitude of the geographic location or a configured date value, wherein the configured date value comprises: an acquisition date associated with the location information, a future date associated with the acoustic survey, or a pre-determined date.
10 . The method of claim 1 , wherein: the time interval is determined using a first offset and a second offset from the time value of solar noon, the first offset and the second offset included in the one or more configured offsets; the first offset is indicative of a difference between the time value of solar noon and a start of the time interval; and the second offset is indicative of a difference between an end of the time interval and the time value of solar noon.
11 . The method of claim 10 , wherein the second offset is greater than the first offset.
12 . The method of claim 1 , wherein a respective size for each of the one or more configured offsets is determined based on one or more of: a latitude associated with the location information, a date or a season corresponding to the time value of solar noon, or depth information of the water column.
13 . The method of claim 1 , wherein the time interval extends from at least one hour before the time value of solar noon to at least two hours after the time value of solar noon.
14 . The method of claim 1 , wherein the time interval comprises a particular portion of a day corresponding to a main solar heating window (MSHW) for the water column beneath the survey vessel, and wherein the MSHW is based on one or more of: a peak solar irradiance of the water column occurring during the particular portion of the day; a maximum potential for solar energy absorption within the water column occurring during the particular portion of the day; or a maximum rate of temperature change associated with the water column occurring during the particular portion of the day.
15 . The method of claim 1 , further comprising: determining, based on the time value of solar noon, an expected rate of change in one or more characteristics of the water column; and determining one or more of the time interval or the second sampling periodicity based on the expected rate of change.
16 . The method of any claim 1 , wherein one or more of the plurality of sound velocity profile measurements are obtained using respective sampling periodicities that are shorter than the first sampling periodicity and longer than the second sampling periodicity.
17 . The method of claim 1 , further comprising: processing the plurality of sonar measurements to generate a corresponding plurality of refraction corrected sonar measurements, wherein generating the corresponding plurality of refraction corrected sonar measurements includes: processing a first subset of the plurality of sonar measurements using the first subset of the plurality of sound velocity profile measurements, to thereby generate a first subset of the corresponding plurality of refraction corrected sonar measurements; and processing a second subset of the plurality of sonar measurements using the second subset of the plurality of sound velocity profile measurements, to thereby generate a second subset of the corresponding plurality of refraction corrected sonar measurements.
18 . The method of claim 17 , wherein: the first subset of the plurality of sonar measurements and the first subset of the plurality of sound velocity profile measurements are obtained outside of the time interval; and the second subset of the plurality of sonar measurements and the second subset of the plurality of sound velocity profile measurements are obtained within the time interval.
19 . A system comprising: at least one processor; and a memory storing instructions which, when executed by the at least one processor, cause the at least one processor to: obtain location information associated with one or more of a survey vessel or an acoustic survey associated with the survey vessel; determine a time value of solar noon associated with the location information, wherein the time value of solar noon is determined based on the location information; determine a time interval corresponding to increased water column heating from solar irradiance of a water column beneath the survey vessel, wherein the time interval is determined using one or more configured offsets from the time value of solar noon; and perform the acoustic survey to obtain a plurality of sonar measurements and a plurality of sound velocity profile measurements within the water column, wherein: a first subset of the plurality of sound velocity profile measurements is obtained outside of the time interval and using a first sampling periodicity; and a second subset of the plurality of sound velocity profile measurements is obtained within the time interval and using a second sampling periodicity, wherein the second sampling periodicity is shorter than the first sampling periodicity.
20 . The system of claim 19 , wherein the instructions further cause the at least one processor to: compare a current time value to the determined time value of solar noon; and control, based on the comparison, a winch system attached to the survey vessel and configured to deploy a towed sound velocity profiler (SVP) from the survey vessel into the water column, wherein the instructions cause the at least one processor to control the winch system to: deploy the towed SVP using the first sampling periodicity in response to the comparison indicating that the current time value is outside of the time interval; and deploy the towed SVP using the second sampling periodicity in response to the comparison indicating that the current time value is within the time interval.

Description

FIELD Aspects of the present disclosure generally relate to underwater sensing and/or acoustic surveying acquisition systems and methods of use thereof. For example, aspects of the present disclosure are related to systems and techniques for adjusting a sampling periodicity of an underway profiling device based on a local solar noon (LSN) time value and/or a main solar heating window of a surveyed water column. Unlocking insights from Geo-Data, the present invention further relates to improvements in sustainability and environmental developments: together we create a safe and liveable world. BACKGROUND Marine surveying and/or other geophysical surveying performed in a marine or underwater environment can involve the collection of acoustic positioning and/or bathymetry data. Bathymetry data can be used for the measurement and study of the seafloor (or the floors of other bodies of water in which the bathymetry data is collected). For example, bathymetry data can be used to map depth contours of the seafloor, similar to the elevation contours mapped by topography data collected for land-based environments, while acoustic positioning data can be used to track items or objects in the water such as towed scientific instruments or uncrewed underwater vehicles (UUVs), among various others. Sonar bathymetry surveys can use multibeam echosounders and/or various other sonars or acoustic sensors to map underwater terrain based on emitting multiple beams (e.g., sound waves) that travel through the water column, reflect off the seafloor, and travel once again through the water column on a return path back to the sonar head. The time taken for these sound waves to travel to the seafloor and reflect back can be used to calculate depth, by using the speed of sound in the water column to convert the time value into a distance value. Accurate depth or distance determination in a sonar bathymetry survey or acoustic positioning operations can require accurate information characterizing the sound speed within the water column, and sound waves may refract according to variations in water density, temperature, salinity, etc., within the water column. Errors or inaccuracies in the sound speed information used to process sonar or other acoustic survey data can result in distortions of the calculated angles and ranges of the sonar beams. Such distortion can vary with the sonar beam angle, with the depth inaccuracies increasing with the beam angle. Sound speed errors in bathymetric surveys and/or acoustic positioning operations can correspond to environmental factors such as temperature and salinity gradients. For example, in a layered or stratified water column, different layers can vary in sound speed, particularly when a thermocline is present. Thermoclines may occur when surface water layers absorb heat or are otherwise heated at a greater rate than deeper water layers. The surface heating effect can create rapid temperature changes at relatively shallow water depths within the surface or near-surface layers of the water column, and increased temperature gradients along the depth of the water column. These temperature differences correspond to increases in the sound speed in the warmer upper layer(s) relative to the cooler lower layer(s) of the water column, causing sound waves to bend and refract away from the expected straight-line path. The “afternoon effect” can refer to errors in acoustic instrument data caused by sound speed changes that result from transient thermoclines formed under calm, sunny conditions. The afternoon effect can correspond to solar heating of the upper and/or surface ocean layers in the absence of mixing (e.g., due to calm conditions with low wind), which creates a temperature gradient (e.g., transient thermocline) near the surface. MBES and other sonar transceivers are commonly operated within this same surface or near-surface layer of the water column, and the transient thermocline or temperature gradient associated with the afternoon effect refracts acoustic waves downward, negatively impacting the sonar performance as both transmitted and reflected (e.g., outgoing and incoming) sonar pulses are directed away from the sonar array due to refraction at the thermocline. Transient thermoclines may develop and dissipate according to various meteorological and oceanographic conditions, including solar radiation intensity, wind speed, cloud cover, tidal influences, etc., and the sound speed profile within a water column may be highly variable in magnitude and/or rate of variation. There is thus a need to address at least one of the problems described above by providing a solution for uncertainties in the sound speed profile within a water column to more accurately translate acoustic data into distance data. SUMMARY The following presents a simplified summary relating to one or more aspects disclosed herein. Thus, the following summary should not be considered an extensive overview relating to all contemplat