Pipeline & Underground
Advanced IMU/odometer sensor fusion for pipeline inspection gauge (PIG) surveys, in-line inspection georeferencing, and underground mapping. Iterative optimal smoothing with integrated slip detection and control point support.
Why AlgoNav for Pipeline Inspection?
Pipeline inspection gauges carry no GNSS receiver — trajectory quality depends entirely on how well IMU and odometer data are fused, and that is where AlgoNav excels.
Iterative Optimal Smoothing
Standard forward-backward smoothers make a single pass in each direction. AlgoNav goes further with iterative multi-pass estimation, progressively refining IMU error models and distributing residual errors across the full trajectory while anchoring the solution at entry, exit, and intermediate control points — producing tighter trajectories than standard approaches.
Advanced IMU Error Modeling
Standard inertial processing models only accelerometer and gyroscope biases — if at all. AlgoNav supports extended sensor error models including scale factors and misalignment angles. These parameters are determined through guided field calibration procedures — simple orientation sequences before or after a campaign that AlgoNav processes into hardware-specific corrections. Over long pipeline runs, this calibration significantly improves trajectory quality.
Multi-Odometer Fusion & Slip Detection
PIGs typically carry two or three odometer wheels that roll along the inner pipe wall. Wheel slip — caused by debris, liquid films, or pipe irregularities — is inevitable and corrupts distance measurements. AlgoNav integrates multiple odometers simultaneously with built-in slip detection, automatically weighting and selecting the most reliable distance information to produce the best possible trajectory without manual quality checks.
Control Point Integration
AlgoNav supports two types of control points: external markers that detect when and where the PIG passes through a known location along the pipe, and surveyed pipe coordinates from RTK or total station measurements at above-ground features. Both types are fused directly into the trajectory estimation, constraining the solution at known positions and significantly reducing along-pipe drift.
Works with Any IMU in Your Inspection Tool
Pipeline inspection gauges are built with IMUs from different manufacturers — from high-end navigation-grade sensors to purpose-built inspection IMUs. AlgoNav works with any IMU providing an open or documented data format, without requiring you to change your existing inspection hardware.
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Why Post-Processing Is Essential
Unlike surface applications, pipeline inspection has no real-time alternative. The PIG travels through the pipe without any live data link — all sensor data is recorded onboard and processed after retrieval.
Post-Processing Is Not Optional — It Is the Only Method
A pipeline inspection gauge is not connected to any external system during its run. PIGs carry no GNSS receiver — the only inputs are onboard IMU and odometer data, together with known coordinates at entry, exit, and intermediate control points. All trajectory computation happens after retrieval.
This is where AlgoNav's iterative optimal smoothing delivers its greatest advantage: by processing the complete recorded dataset in both directions, the algorithm can use information from the entire run — including future observations — to minimize drift and resolve ambiguities that a forward-only filter could never address. Combined with advanced IMU error modeling and multi-odometer slip detection, this produces trajectories of a quality that would be physically impossible to achieve in real time, even if a data link existed.
Challenges We Solve
Pipeline inspection operates in conditions where standard positioning approaches simply do not apply. AlgoNav's algorithms are built for these extremes.
Kilometer-Scale Inertial Navigation
Pipeline runs can extend over tens of kilometers with no external position updates beyond control points. Inertial drift over these distances is the dominant error source. AlgoNav's iterative optimal smoothing distributes residual error across the entire run by processing from both ends and anchoring at all available control points — rather than letting drift accumulate unbounded from one side.
Odometer Wheel Slip
Odometer wheels inside the pipe are prone to slip from debris, condensation, wax buildup, and pipe irregularities. AlgoNav models odometry as true position increments — not simplified velocities — and fuses multiple odometers with integrated slip detection. The algorithm automatically identifies and down-weights degraded distance measurements to maintain trajectory quality.
No IMU Alignment Needed
Traditional inertial systems require lengthy static alignment procedures before launch — time that is costly and often impractical in field conditions. AlgoNav resolves initial orientation directly from the recorded data during iterative post-processing. No static warmup, no gyro-compassing hardware — the PIG can be launched immediately.
3D Curvature & Bend Measurement
Accurate measurement of pipeline bends, elevation changes, and 3D curvature is essential for strain analysis and integrity assessment. AlgoNav's high-rate attitude solution captures the full geometry of every bend, tee junction, and vertical transition along the run — directly supporting dent and strain reporting to pipeline integrity standards.
Control Points & Above-Ground Markers: Anchoring the Trajectory
Field teams install above-ground markers (AGMs) or electronic transmitters that detect when the PIG passes a known location inside the pipe. Additionally, pipe coordinates may be known at valve stations, road crossings, or other surveyed features. AlgoNav integrates both types of control points — passage markers and known pipe coordinates — directly into the trajectory estimation. Each control point acts as an anchor that constrains along-pipe and cross-pipe position, significantly reducing accumulated drift and tying anomaly locations to absolute coordinates for excavation planning and regulatory reporting.
Let's Talk
Whether you need PIG inspection georeferencing, tunnel survey processing, or HDD as-built documentation — AlgoNav delivers precision where satellites cannot reach.