Hydrography & Marine
Post-processed GNSS/INS positioning for bathymetric surveys, offshore operations, and inland waterway mapping. True heave compensation, IHO S-44 compliant trajectories, and PPP-based positioning far from shore — on open ocean, coastal waters, rivers, and lakes.
Why AlgoNav for Hydrography & Marine?
Robust positioning and precise vessel attitude for survey-grade bathymetric mapping — from deep-water offshore campaigns to river channel surveys.
True Heave & Vessel Motion
Accurate heave, roll, pitch, and heading are critical for multibeam echo sounder georeferencing. Real-time heave sensors (MRUs) suffer from drift over longer survey lines and cannot use future data to separate vessel dynamics from positioning error. AlgoNav's post-processed true heave uses iterative optimal smoothing of high-rate IMU and GNSS data to deliver drift-free vertical motion — directly reducing Total Vertical Uncertainty (TVU) in your sounding dataset.
Multibeam Bathymetry & Sonar
Per-ping position, attitude, and timing for multibeam and side-scan sonar workflows. AlgoNav can ingest actual sonar ping timestamps and interpolate the trajectory solution directly to these exact time marks — no high-rate output or external interpolation needed. The result is position, heading, roll, pitch, and heave precisely at each ping, ready for direct integration into bathymetric processing software like QPS Qimera, CARIS HIPS, or Teledyne PDS.
Offshore Wind & Construction
Centimeter-level positioning for every phase of offshore construction — geotechnical site investigation, monopile foundation installation, inter-array cable routing, and long-term structural monitoring. PPP provides geodetic-quality results hundreds of kilometers from shore, without dependency on shore-based reference stations.
Rivers, Lakes & Inland Waterways
Bathymetric surveys on rivers, canals, reservoirs, and in harbors face GNSS conditions that are often more challenging than open water — bridges, lock chambers, and dense riverbank vegetation cause frequent signal obstructions. AlgoNav's tightly-coupled INS bridges these outages to maintain continuous survey trajectories where real-time solutions would drop.
Works with Any Vessel Motion Reference System
Survey vessels use GNSS receivers and MRUs from different manufacturers. AlgoNav processes data from any GNSS or IMU with an open or documented format — including motion reference units from the leading marine sensor manufacturers — without requiring hardware replacement.
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Real-Time vs Post-Processed Sensor Fusion
In marine surveying, the quality of your trajectory — position, attitude, and heave — is determined by how well GNSS, IMU, and auxiliary sensors are fused. Post-processing produces fundamentally better results than any real-time filter.
Real-Time Sensor Fusion
Forward-only filtering during operations
- Real-time heave is computed by double-integrating accelerometer data — a process that inherently drifts, producing low-frequency bias that cannot be corrected without future observations
- Forward-only Kalman filtering cannot use future IMU and GNSS data to improve attitude and position estimates — accuracy degrades during any sensor interruption with no recovery until conditions improve
- Real-time PPP atmospheric models are less accurate than final products, limiting absolute vertical positioning — critical for depth accuracy
- All data links between GNSS receiver, IMU, and sonar must work continuously and synchronously — operationally demanding on moving vessels
- Survey vessel time is expensive — any quality issue discovered later that requires re-survey doubles operational costs
Post-Processed Sensor Fusion
Iterative optimal smoothing of all sensor data
- True heave through iterative optimal smoothing of high-rate IMU data eliminates drift entirely, producing bias-free vertical motion — directly reducing TVU in sounding datasets
- Attitude (roll, pitch, heading) benefits from the same bidirectional estimation, delivering more stable and accurate vessel orientation than any real-time filter
- GNSS outages near offshore structures, in ports, or under bridges are seamlessly bridged using tightly-coupled inertial data from both sides of the gap
- PPP with final precise products models atmospheric delays more accurately than real-time corrections, improving absolute vertical accuracy
- Each sensor simply logs data independently — no inter-sensor data links required, much simpler to operate at sea
- IHO S-44 compliant accuracy documentation with traceable uncertainty estimates
When to Use Which?
Use real-time fusion for dynamic positioning, dredging guidance, and operations that require immediate feedback for vessel control.
Use post-processed fusion for all hydrographic surveys, bathymetric mapping, and offshore construction where trajectory quality, true heave, and attitude accuracy determine the final data product. Post-processing consistently outperforms real-time solutions — especially in vertical accuracy and heave stability.
Near shore and inland: Where reference station data is available, PPK processing delivers centimeter-level accuracy for port surveys, river channel mapping, and coastal engineering projects.
Challenges We Solve
Maritime and waterway positioning presents unique obstacles that land-based systems never encounter. AlgoNav's algorithms are purpose-built for these conditions.
True Heave & Motion Compensation
Real-time heave sensors (MRUs) compute heave by double-integrating accelerometer data — a process that inherently drifts over time and cannot be corrected without future observations. AlgoNav's post-processed true heave uses bidirectional GNSS/INS smoothing to eliminate this drift, producing a clean, bias-free vertical motion signal. This directly reduces TVU in your multibeam sounding dataset and is a key requirement for NOAA HSSD and IHO S-44 compliance.
Offshore PPP Without Shore Infrastructure
Hundreds of kilometers from the nearest reference station, PPP is the only viable positioning method. Post-processed PPP with final precise orbit and clock products models ionospheric and tropospheric delays far more accurately than real-time corrections, delivering robust sub-decimeter vertical accuracy — critical for bathymetric surveys where vertical uncertainty directly affects chart quality.
No IMU Alignment Needed
Real-time INS systems require 10–20 minutes of static alignment before each survey line — idle time that accumulates quickly on multi-line campaigns. AlgoNav resolves initial orientation directly from the logged data during post-processing, eliminating the need for gyro-compassing or static warmup in port or at the survey area.
Vertical Datums & Tidal Reductions
Hydrographic deliverables require depth referenced to chart datum — not ellipsoidal height. AlgoNav applies geoid models and tidal reductions to convert from GNSS ellipsoidal heights to chart datums such as LAT, MSL, or local low water references. Combined with true heave, this ensures consistent depth georeferencing across acquisition, processing, and final deliverables.
Instant Post-Processing: Rapid PPP On Board
For time-sensitive operations — such as dredging progress monitoring or pre-clearance surveys — waiting days for final precise products is not practical. AlgoNav supports instant post-processing using rapid or ultra-rapid orbit and clock products that are available within hours. This delivers a preliminary trajectory with improved accuracy over real-time solutions, allowing field teams to assess data quality and make operational decisions the same day. Once final precise products become available (typically after 12–14 days), the same data can be reprocessed for maximum accuracy without revisiting the survey area.
Let's Talk
Discover how AlgoNav supports hydrographic surveys, offshore operations, and inland waterway mapping with positioning solutions built for the unique demands of the marine environment.