fls_ism

Inverse Sensor Model for Forward-Looking Sonar (FLS). Converts raw sonar polar images into probabilistic point clouds and voxel-based occupancy maps for AUV perception.

Dependencies

sudo apt-get install ros-jazzy-image-transport ros-jazzy-cv-bridge ros-jazzy-tf2-ros libboost-all-dev ros-jazzy-tf-transformations
pip install scipy

Nodes

fls_pcl_node — fls_ism/fls_pcl.py

Main processing node. Subscribes to raw sonar images and outputs probabilistic point clouds.

Subscribes

Type	Description
Image	Raw polar sonar image
Ping	Sonar metadata (bearings, range) — real hardware only
Marker	Voxel FOV geometry from fls_voxel_node

Publishes

Type	Description
PointCloud2	Voxel-based probabilistic cloud (intensity = occupancy probability)
PointCloud2	Peak intensity per azimuth beam
PointCloud2	Unfiltered sonar image as points
Image	Preprocessed sonar image

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fls_voxel_node — fls_ism/fls_voxels.py

Publishes the sonar FOV geometry as a voxel marker grid. Runs once on startup with a latching QoS so downstream nodes receive it on connect.

Publishes

Type	Description
Marker	3D voxel grid covering the sonar cone

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Launch Files

fls_ism.launch.py

Starts fls_voxel_node and fls_pcl_node under the alpha_rise namespace. Primary launch file for online sonar processing (live hardware or bag replay).

ros2 launch fls_ism fls_ism.launch.py

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Configuration

config/fls_params.yaml

Shared parameters for fls_pcl_node and fls_voxel_node.

Parameter	Default	Description
sim	false	Simulation mode — skips image preprocessing, derives bearings from image width
vertical_fov_deg	12.0	Vertical beam FOV (degrees)
horizontal_fov_deg	70.0	Horizontal FOV (degrees)
range_max	40.0	Max sensor range (m)
resolution	1.0	Voxel side length (m)
threshold_intensity	30	Minimum pixel intensity (0–255)
threshold_min_range	5.0	Minimum range filter (m)
max_depth / min_depth	-1.0 / -15.0	World-frame depth bounds (ENU, m)
lower_bound_intensity	56	Intensity mapped to min_probability
upper_bound_intensity	100	Intensity mapped to max_probability
min_probability	0.2	Minimum occupancy probability output
max_probability	0.9	Maximum occupancy probability output
frequency	1.2e6	Sonar frequency (Hz)
sound_speed	1500	Speed of sound (m/s)
aperture_size	0.0067	Aperture size for sinc beam directivity (m)
save_as_pcd	false	Accumulate and save cloud to PCD on shutdown

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