Updated: This article explains how to perform boresight calibration using OxTS Georeferencer to improve the angular and linear accuracy of LiDAR pointclouds.
OxTS Georeferencer supports two boresight calibration methods:
Targeted Boresighting (using retroreflective targets)
Targetless Boresighting (Beta) (using flat environmental surfaces)
Both methods refine the angular (LIR) and optional linear (LIP) configuration of the LiDAR relative to the INS.
This process is carried out using OxTS Georeferencer. See here for a useful webinar on boresighting.
A Boresight Calibration training video can be found here:
https://www.youtube.com/watch?v=oehcbycYzqo
An example of the improvement boresight calibration gives a LiDAR survey. UAV survey before (left) and after (right) boresighting.
This feature of OxTS Georeferencer is a calibration technique that OxTS have developed in-house. The calibration corrects the user's angular and linear configuration measurements of the LiDAR device in the INS frame. These values are saved in an LIR and LIP file respectively.
A full guide for using OxTS Georeferencer can be found here. Some information useful for boresighting may be included here instead.
OxTS Georeferencer includes an OxTS-developed boresight calibration that refines the LiDAR’s angular (LIR) and optional linear (LIP) alignment in the INS frame. The calibrated values are saved to .lir and .lip files. For broader software instructions, see the full Georeferencer guide.
LIP calibration (Beta)
Georeferencer 1.2 (October 2020) introduced LIP displacement calibration (Beta). By default, Georeferencer calibrates angles only. To enable LIP calibration, select it in Processing Options. The workflow is otherwise the same. Calibrate LIR first, then run LIP only if needed.
What is Boresighting?
Boresight calibration is an OxTS-developed technique used to correct mounting measurement errors between a LiDAR and an INS. The calibration produces improved values for:
LIR (LiDAR-to-INS angular offsets: yaw, pitch, roll)
LIP (LiDAR-to-INS linear offsets: x, y, z) (optional, Beta)
These values are written to the LIR and LIP configuration files and used when generating the final LAZ pointcloud.
Examples of boresighting results
UAV survey before and after boresighting showing an elimination of 'double-vision'.
A comparison of an East (red) and West (blue) drive down a road. In this before and after comparison you can see clearly how the error increases linearly with range and how the frames are perfectly aligned after the calibration has taken place.
Before you Begin
For best results, ensure the following before collecting any boresight data:
Collect data in open-sky conditions with minimal GNSS multipath.
Use RTK (RINEX) corrections and maintain centimetre-level (integer) accuracy during the run.
Complete an INS warm-up and confirm the system is operating within specification (for example, check heading/position/pitch/roll accuracies in NAVdisplay and in post-processing via NAVgraph).
Use appropriate GNSS antenna installation practices (for example, ground planes where required).
Calibration accuracy depends directly on navigation quality. Do not proceed if the navigation solution is not within specification.
Choose Boresight Method
For best results, ensure the following before collecting any boresight data:
Targeted boresighting
Use two square retroreflective targets. This method is best when you need repeatable results and fast validation.
Targetless boresighting (Beta)
Use two or more flat surfaces in the environment (for example, ground + wall) that are not collinear. This method is useful when targets cannot be deployed, but results depend heavily on feature quality and coverage.
What is Required?
Required
A LiDAR device compatible with OxTS Georeferencer
An OxTS INS with the boresight calibration feature enabled
OxTS Georeferencer (download via OxTS)
Navigation processing via NAVsolve (NCOM + VAT output)
Additional requirements for targeted boresighting
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Two flat retroreflective targets, recommended size 80 cm × 80 cm
Flat (not warped)
Retroreflective (tape recommended)
Stationary (do not allow movement during the run)
Non-reflective on the back side (to avoid interference)
Summary of Boresight Workflow
Use the following workflow for both methods.
Warm up the INS and verify navigation accuracy is within specification.
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Collect a boresight dataset:
INS logging (RD/NCOM) and LiDAR logging (PCAP or LCOM)
Manoeuvres that give the LiDAR many views of the features (targets or surfaces)
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In Georeferencer, load:
NCOM, VAT, PCAP/LCOM, LIR, LIP (if used)
Run Boresight Calibration and complete the selection step (targets or surfaces).
Generate a before/after validation pointcloud to confirm improvement.
Use the calibrated configuration files for future surveys.
Boresight Data Collection
General guidance (all methods)
To obtain a good calibration result, the LiDAR must observe the features from many angles and a range of distances.
Recommended practices:
Do not start or stop the recording while the features are in view.
Speed is not critical (typical vehicle surveys are 5–25 mph).
Aim for 3–5 minutes minimum of manoeuvres; longer can help when practical.
Use loops, serpentine paths, and approaches from both sides.
For limited-FOV sensors (for example, Livox), ensure the LiDAR sees the features for several minutes within the run.
Targeted-Boresighting: Setup and Data Collection
Set up targets
Place targets at least 5 m apart.
Use different orientations if possible (ideally near right angles and slightly tilted).
Choose a distance similar to your survey environment (for example, roadside objects at ~10 m → collect at 2–30 m).
An example of a set up including two targets at right angles.
Collect data
Ensure INS and LiDAR are logging.
Drive/fly manoeuvres to maximise perspectives of both targets.
The NCOM data is shown on Bing maps. This is a typical driving pattern for a boresight calibration. Pink circles have been added to show where the targets are.
Example of manoeuvres for a boresight calibration with a 360° FOV LiDAR. The grey line is the vehicle's trajectory and the yellow dots are the locations of the targets.
Motion image of the vehicle trajectory for a boresight calibration. The targets are within the driving pattern and driven round on both sides for maximum perspective exposure.
Targetless-Boresighting (Beta): Setup and Data Collection
Targetless boresighting follows the same general process as targeted boresighting, but uses flat environmental surfaces instead of targets.
Requirements
-
The boresight area must include two (or more) flat surfaces that are not collinear.
Example: ground plane + at least one wall
Recommended run structure (Beta)
Complete an INS warm-up before the boresight run.
Perform a 10-minute drive in the boresight area.
-
Use a series of manoeuvres around the features:
Figure-of-eights
Straight lines with varying approach angles
Repeated passes to vary range and heading relative to the surfaces
Configuration Files (LIP and LIR)
Create files
Open the Files tab in Georeferencer.
Select the plus (+) icons to create LIR and LIP files.
Edit and review values in Hardware Configuration.
LIP file (linear offsets)
The LIP file contains:
X displacement
Y displacement
Z displacement
A calibration flag (0 = uncalibrated, 1 = calibrated)
Measure from the INS measurement point (shown on the INS exterior), not the physical centre of the unit.
LIR file (angular offsets)
The LIR file contains:
Yaw offset
Pitch offset
Roll offset
A calibration flag (0 = uncalibrated, 1 = calibrated)
Use the LiDAR manual to confirm axis orientation. If a LiDAR 3D model is available in Georeferencer, use it to validate your setup.
Processing
Prepare navigation data
Process navigation data in NAVsolve (use base station files where applicable).
Export NCOM.
Run calibration
-
In Georeferencer, load:
NCOM, VAT, PCAP/LCOM, LIR (and LIP if used)
Confirm the files are synchronized.
Select your boresight method and which file to optimize in the processing options.
Select Run Boresight Calibration.
-
Complete the selection step:
Targeted: confirm the two target clusters and adjust search radii as needed.
Targetless (Beta): Ensure the flat surfaces are selected using the selection bubbles
After processing:
Georeferencer updates the LIR (and LIP if enabled)
A processing folder is created containing original and calibrated files
You can run georeferencing to output a LAZ pointcloud with the optimised configuration
The targets are seen as a cluster of points inside a searching radius. Retroreflective strips on our airfield can also be seen. Red points are retroreflective points in the LiDAR data, grey points are the vehicle trajectory, the yellow circles are where the software has currently located the boresight targets and the blue circles are boresight search radii (within which only and all of the target should be contained).
Check Your Boresight (recommended)
To quickly validate your boresight, you can check the "Targets-Only" pointcloud. This is produced when you run the boresight; The 'mobile_targets.laz" file can be found in the boresight working folder. Targets should appear flat and square with minimal smearing.
Advanced Settings
Several boresight parameters can be adjusted, but default values are recommended unless you understand their impact.
Common adjustments:
Reflectivity threshold: This can be adjusted if too many non-target objects appear.
Minimum/maximum range: This can be used to remove vehicle returns or reduce long-range noise.
Reducing maximum range can improve accuracy slightly if the LiDAR becomes noisy near its limit.
Troubleshooting
Too many objects appear during targeted boresight selection
Increase the reflectivity threshold in Processing Options.
Set a minimum range if the LiDAR is capturing parts of the vehicle.
Example clusterplot with the default reflectivity threshold of 100 using a VLP32. Instead of just the targets many objects show up.
Target smearing or unclear clusters
This usually indicates one of the following:
Incorrect initial LIR
A time offset between LiDAR and navigation data
Navigation data quality is not within specification
Warm-up period is missing from the dataset
Actions:
Re-check LiDAR axis definitions and initial LIR values using the LiDAR manual.
Confirm time synchronisation (PTP implementations can introduce offsets on some devices).
Remove early data where the INS may still be warming up.
Verify navigation accuracy is stable throughout the run.
Contact OxTS
Contact OxTS for information on troubleshooting a boresight calibration, obtaining survey-grade INS devices or to share your boresighting data with us or test some of our data sets.
- support@oxts.com for technical support with performing a boresight calibration
- sales@oxts.com for sales enquiries
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