Offshore and coastal construction requires an understanding of ocean conditions to make no-go decisions on safety and compliance.
Spatial and temporal data gaps increase exposure to incorrect calls and raise the risk of a shutdown, costing companies delays and lost profit. Spotter provides a solution: real time current and acoustic data that supports data-informed decisions in critical situations.
The acoustic Doppler current profiler (ADCP) has been the standard tool for measuring currents for thirty years. However, technical limitations often prevent near surface current measurements and make it difficult to retrieve the data in real-time, creating a substantial data gap for marine and coastal construction.
A bottom mounted ADCP looks up, and its beams pick up a reflection off the sea surface that corrupts the top of the profile. How much is lost scales with the distance to the surface, so the deeper the water, the bigger the gap.
Instruments mounted looking down from a vessel or a platform lose more. The transducer sits below the waterline, the first few meters of every ping are blanked out, and any structure in the beam, a leg or a pile or a mooring line, pulls the measurement toward zero.
The standard procedure is to extrapolate up from the shallowest good measurement, which does not always hold due to wind driven shear and other physical processes near the surface.
The surface layer that ADCPs miss are often critical for construction operations. Currents in that part of the water column push vessels off position during station keeping and dynamic positioning. They load crane barges, jack ups, and tow lines. They control cable lay and touchdown and scour protection placement. They decide whether a small boat transfer, a dive, or a remotely operated vehicle window is workable, and they carry a spill, a sediment plume, or a dropped object away from where it went in.
Every one of those is a go or no go call against a threshold, made in the one layer the instrument on the seabed cannot reach. Modeling is not always a robust solution as a surface forecast is only as good as the observations behind it.
A Spotter with a current sensor on a Smart Mooring floats at the surface and measures that layer directly, in real time over cellular and satellite. The Spotter is an easy to deploy solution that gives you the surface layer that drives set, drift, and workability, all in real-time.
The accuracy is independently verified. Integral Consulting deployed a Spotter with an Aanderaa current sensor next to a Teledyne RDI Sentinel Workhorse ADCP off Santa Barbara for 24 days. Current speeds matched with an R² of 0.904, with low bias and low root mean square difference in both speed and direction.
Spotter also provided data directly to the dashboard in real time. The ADCP data could not be read until the instrument was recovered, and gaps in data due to a loss of power was not realized until after retrieval.
Underwater sound monitoring is now standard practice on marine and coastal construction. No United States statute names an acoustic baseline, but the requirement arrives through incidental take authorizations under the Marine Mammal Protection Act, Endangered Species Act consultation, National Environmental Policy Act analysis, and Bureau of Ocean Energy Management plan review. The Bureau expects in situ sound field verification for impact pile driving, measured against modeled predictions at multiple ranges and azimuths. Individual project authorizations go further, calling for real time passive acoustic monitoring before, during, and after pile driving, interim measurement reports within 48 hours, and listed species detections reported within 24. Joint recommendations from the National Oceanic and Atmospheric Administration and the Bureau ask for an ambient ocean noise baseline established 3 to 5 years before construction and recorded continuously.
Most of that work is carried out with an archival bottom recorder. The recorder is placed on the seabed, records to internal storage on a fixed schedule, and is recovered by vessel at the end of the deployment, when the data is finally downloaded and analyzed.
An archival recorder documents a season well, but it cannot support a decision while that season is underway. The data stays on the seabed until the instrument is recovered, so it cannot trigger a shutdown, confirm an exclusion zone is clear, or show that a threshold was crossed on the day it happened. Industry data management practice assumes detection and ambient noise products arrive within 90 days of retrieval, which leaves months between sound in the water and a reportable result.
Recovery takes a vessel and a weather window, and any problem with the instrument surfaces only once it is on deck. A flooded housing, a dead battery, or a gain set incorrectly can cost an entire deployment, with no indication while the work was still going on.
Duty cycling introduces a second limitation. Recording two minutes of every hour to conserve power and storage leaves 97 percent of the time unmonitored, and those gaps fall across the events that matter most, including the start of a pile driving sequence and the first call of an animal entering the zone. This is why the joint recommendations ask for continuous recording, and why a duty cycled record makes a weak foundation for a baseline.
Spotter Sound is a hydrophone on a Smart Mooring beneath a solar powered Spotter. The hydrophone sensor sits at the depth the work requires, records continuously rather than on a duty cycle, and the Spotter reports over satellite and cellular from the day it is deployed.
The sample rate is configured to the species or signal being monitored. Vessel machinery and propellers sit between 10 and 500 Hz, dolphin whistles reach 20 kHz and need at least 40 thousand samples per second, and harbor porpoise clicks near 130 kHz need 260 to 500 thousand. Matching the setting to what the permit covers keeps the record usable for the species that matter on that site.
Continuous recording produces far more data than a satellite link can carry, roughly 11 GB a day per channel at 62.5 thousand samples per second, against a satellite message of a few hundred bytes. Spotter Sound resolves this by running detection models on the instrument. Acoustic detections on the edge reduces each event to a timestamp, a label, and sound levels in standard frequency bands, a few kilobytes that transmit immediately, while the full rate recording stays on the device for the archive and the compliance report.
Real time reporting is what changes the work on an active site. Spotter Sound puts a marine mammal detection or a noise exceedance in front of the person who can stop the hammer while the pile is still being driven. Solar power allows for continuous monitoring without the need to replace batteries and the instrument can be reconfigured remotely instead of recovered and redeployed.
Spotter Sound provides the ambient ocean noise baseline, records continuously from site characterization through construction, and is provides real-time data for concurrent decision making.
Both gaps are the same failure in different units. The ocean was measured well and reported late, or measured everywhere except the depth that mattered. Closing either one used to take a survey vessel, a specialist crew, and a six figure instrument. It now takes a Spotter two people can deploy in an afternoon, reporting while the decision is still open.
Talk to our team about metocean and acoustic monitoring for your next project
