Airborne Geophysics
Post-processed GNSS/INS trajectories for airborne survey aircraft carrying cameras, LiDAR, ground-penetrating radar, magnetometers, and gravimeters. Precise position and attitude for sensor georeferencing — plus deep expertise in strapdown airborne gravimetry.
Why AlgoNav for Airborne Geophysics?
Airborne surveys require more than just a position — they need precise attitude, smooth trajectories, and trajectory states delivered exactly at each sensor event.
Gimbal-Mounted Sensors & Multi-IMU
Survey aircraft often carry cameras, LiDAR, or radar on gimbal platforms with a variable lever arm. AlgoNav supports two approaches: dual-IMU processing with one IMU fixed to the airframe and one to the sensor, or ingestion of gimbal encoder readings to compute the time-varying lever arm. Both methods deliver accurate position and attitude at the sensor itself — not just at the aircraft body frame.
Sensor Timestamp & Position Interpolation
AlgoNav can ingest the exact trigger timestamps of cameras, radar pulses, or LiDAR scans and interpolate the trajectory solution to these precise time marks. Beyond temporal interpolation, the software also computes trajectories at the physical location of the sensor(s) — accounting for lever arm, orientation offsets, and platform dynamics — so the output is directly usable for sensor georeferencing without additional post-steps.
PPP & PPK for Remote Surveys
Many geophysical surveys operate far from reference station networks — polar regions, open ocean, dense jungle, or developing countries. AlgoNav's PPP processing delivers survey-grade accuracy without any local base station. Where reference stations are available, PPK provides centimeter-level results. Both modes produce final trajectories through iterative optimal smoothing with precise satellite products.
No IMU Alignment Needed
Real-time INS systems require static alignment on the ground before takeoff — idle time that delays flight operations. AlgoNav resolves initial orientation directly from the recorded data during post-processing, eliminating the need for static warmup or gyro-compassing procedures before each flight.
Supports Sensors from All Major Manufacturers
Airborne geophysical operators use a wide range of GNSS receivers and navigation-grade IMUs. AlgoNav works with any sensor providing an open or documented data format — from high-end gravimetry IMUs to light-aircraft-grade systems — with no vendor lock-in.
All product and company names are trademarks™ of their respective owners.
Strapdown Airborne Gravimetry
A core competence of the AlgoNav team — with over 12 years of continuous research, development, and operational experience.
What Is Strapdown Gravimetry?
Strapdown airborne gravimetry uses navigation-grade IMUs rigidly mounted to the aircraft to measure Earth's gravity field directly from the difference between measured specific force and GNSS-derived kinematic acceleration. Unlike platform-stabilized gravimeters, strapdown systems are smaller, lighter, and can be deployed on light aircraft and UAVs — achieving accuracies in the range of 1–2 mGal down to sub-mGal, at spatial resolutions down to a few kilometers.
The quality of the gravity result depends critically on both the GNSS trajectory (for accurate kinematic acceleration and Eötvös correction) and the IMU error modeling (for separating gravitational signal from sensor drift). This is where AlgoNav's iterative optimal smoothing and advanced sensor fusion make the decisive difference — producing smoother, lower-noise trajectories than standard forward-backward approaches, which directly translates to better gravity estimates.
Our Track Record
AlgoNav's team has been advancing strapdown gravimetry since 2014 — developing algorithms, publishing research, and processing operational campaigns in collaboration with institutions including NOAA, the German Federal Agency for Cartography and Geodesy (BKG), and international research partners. We have processed strapdown gravimetry data from campaigns on all continents, covering applications from geoid determination and mineral exploration to coastal zone mapping and polar geodesy. This depth of experience is reflected in our software and in the quality of the results we deliver. See our publications →
Gravity Reductions & Anomaly Output
AlgoNav's strapdown gravimetry processing includes full gravity reductions: latitude correction, free-air correction (altitude reduction), and — as a distinguishing feature — computation of topographic gravity effects. This means the software can deliver either free-air anomalies or complete Bouguer anomalies directly, without requiring external terrain correction tools.
Real-Time vs Post-Processed Sensor Fusion
Many airborne operators rely on the real-time output of their onboard INS. For geophysical surveys, this leaves significant accuracy on the table.
Real-Time INS Output
Forward-only filtering during flight
- Forward-only Kalman filtering cannot use future GNSS and IMU data to improve position and attitude — accuracy degrades during any signal interruption with no recovery until conditions improve
- Real-time PPP atmospheric models are less accurate than final precise products, limiting absolute positioning — especially at flight altitude where ionospheric behavior differs from ground-based models
- Gimbal lever arm compensation in real-time is approximate — full dynamic correction requires post-processed attitude at both IMU locations
- Trajectory smoothness is limited by forward-only estimation — insufficient for gravity processing where Eötvös correction demands the lowest possible noise on velocity and acceleration
- All data links between GNSS, IMU, and survey sensors must work simultaneously — operationally demanding during long survey flights
Post-Processed Sensor Fusion
Iterative optimal smoothing of all sensor data
- Iterative optimal smoothing processes the full dataset in multiple passes, progressively refining IMU error models and producing tighter trajectories than standard forward-backward approaches
- PPP with final precise orbit and clock products for remote operations; PPK with reference station data where available — both deliver survey-grade accuracy
- Atmospheric delays modeled more accurately in post-processing, improving absolute vertical positioning — critical for gravity and altitude-dependent sensors
- Strapdown gravimetry fundamentally requires post-processing — both IMU and GNSS solutions need longer convergence times and multi-pass estimation to achieve the accuracy levels that gravity processing demands. AlgoNav's algorithms provide particularly precise modeling here
- Each sensor simply logs data independently — no inter-sensor data links required during flight, much simpler to operate
When to Use Which?
Use real-time INS only when immediate position feedback is required for flight guidance or sensor triggering.
Use post-processed fusion for all final deliverables — trajectory accuracy, attitude quality, and trajectory smoothness are consistently better in post-processing. For strapdown gravimetry, post-processing is mandatory.
Best practice: Record all raw GNSS and IMU data during every flight. Use the real-time solution for in-flight monitoring, then reprocess with AlgoNav for the final survey product.
Challenges We Solve
Airborne geophysical surveys create positioning challenges that generic GNSS software cannot handle. AlgoNav was designed specifically to address them.
Campaign-Scale Data & Network Adjustment
Geophysical survey campaigns generate dozens of flights and tens of hours of data in grid or line patterns. AlgoNav processes these large datasets in efficient batches — including cloud cluster processing for high throughput. For gravimetry, a campaign-wide network adjustment is supported: crossover statistics are computed across all flight lines and a least-squares adjustment removes residual line biases, delivering a consistent gravity grid across the full survey area.
UAV Transition & Lightweight Sensors
UAVs offer dramatically lower operating costs, no safety risk to crew, and easy deployment in remote or hazardous terrain. The obstacle is sensor quality: UAVs favor lighter, lower-cost IMUs that would typically require expensive real-time systems to compensate. AlgoNav's post-processing algorithms extract survey-grade trajectories from mid-range hardware — making the transition to UAV-based geophysics viable without compromising data quality.
No IMU Alignment Needed
Real-time INS systems require static alignment on the ground before takeoff. AlgoNav resolves initial orientation directly from the recorded data during iterative post-processing — no static warmup, no gyro-compassing hardware. For strapdown gravimetry, a brief ground reading to capture the gravity reference value is the only pre-flight step required.
Remote Area Operations & PPP
From Antarctic ice sheets and Arctic tundra to tropical jungles and open ocean — many survey areas have no reference station infrastructure. AlgoNav's PPP processing with final precise products models ionospheric and tropospheric delays more accurately than real-time solutions, delivering robust sub-decimeter accuracy. Where reference station networks are available, PPK is the preferred mode, delivering centimeter-level precision throughout the campaign.
Instant Post-Processing: Rapid Results in the Field
For time-sensitive survey operations, AlgoNav supports instant post-processing using rapid or ultra-rapid orbit and clock products available within hours. This delivers a preliminary trajectory for early quality assessment and data review — allowing field teams to identify issues and adjust flight plans the same day. Once final precise products become available (typically after 12–14 days), the same data is reprocessed for maximum accuracy without returning to the survey area.
Let's Talk
Whether you are planning a gravity campaign, an aeromagnetic survey, or a high-resolution LiDAR acquisition — AlgoNav delivers the trajectory accuracy your geophysical data requires.