Overview
Terradepth successfully met the Total Vertical Uncertainty (TVU) and Total Horizontal Uncertainty (THU) requirements for International Hydrographic Organization (IHO) S-44 Special Order hydrographic surveys—one of the most stringent benchmarks for hydrographic survey accuracy. The project was enabled by a high-performance AUV autonomy stack incorporating Exail’s PHINS Compact Series inertial navigation and GAPS Series acoustic positioning, with results refined through DelphINS post-processing software suite. Final deliverables were operationalized through Absolute Ocean®, Terradepth’s OceanOS™.
Challenge
High-specification hydrographic surveys typically demand large vessels, onboard crews, and complex logistics. Terradepth set out to meet the IHO Special Order requirements using a fully autonomous AUV-based approach—without sacrificing accuracy.
The mission site lay 60 miles offshore in the Gulf of America, in 80 meters of water—an area affected by hurricanes and active subsea infrastructure. With no local tide stations and no GPS underwater, achieving precise positioning and tidal corrections presented a significant challenge.
Solution
Terradepth used an Ellipsoidally Referenced Survey (ERS) workflow to correct tidal variation and enable high-accuracy autonomous mapping without local tide stations. The AUV achieved precise mapping using advanced multibeam sonar and a maritime autonomy stack built for unmanned operations, incorporating high-grade inertial navigation, embedded fiber-optic gyroscopes, and USBL acoustic positioning for accurate underwater tracking when GPS was unavailable.
Technology from Exail supported this capability through robust navigation, accurate positioning, and DelphINS post-processing software to maintain survey-grade performance throughout the mission.
Results
Terradepth achieved IHO S-44 Special Order TVU/THU compliance using a fully autonomous AUV-based workflow—reducing cost and personnel risk. The AUV achieved 100% bathymetric coverage and reliable feature detection, supporting strict under-keel clearance and seafloor integrity verification.
All mission data and derived outputs were managed through Absolute Ocean®, Terradepth’s Operating System for the Ocean™, enabling secure processing, QA/QC, visualization, and accelerated delivery of validated, decision-ready insights—along with immediate access and secure collaboration.
Total Horizontal Uncertainty
Total Vertical Uncertainty
“Exail’s technologies provided robust navigation, accurate positioning, and post-processing that transformed raw data into precise bathymetric results.”
Steve Giannaris,
Senior Director of Survey Operations, Terradepth