---
license: mit
tags:
- sonar
- underwater-robotics
- self-supervised-learning
- vision-transformer
- sim-to-real
- synthetic-data
- ijepa
- dino
- side-scan-sonar
- autonomous-underwater-vehicle
- cvpr2026
- macvi
datasets:
- bashakamal/ps3-simulator
metrics:
- accuracy
- f1
model-index:
- name: I-JEPA ViT-S/16 PS3
  results:
  - task:
      type: image-classification
      name: Sonar Object Classification
    dataset:
      name: KLSG + SCTD (Real Sonar)
      type: real-sonar
    metrics:
    - type: accuracy
      value: 70.9
    - type: f1
      value: 0.733
---

# PS3 Simulator — Pretrained Sonar Weights

Pretrained ViT-S/16 weights for underwater 
sonar object classification, trained exclusively 
on **synthetic PS3 Simulator data** — 
no real sonar data used at any stage.

Accepted at **MaCVi Workshop @ CVPR 2026**.

---

## What is this?

Real sonar data is expensive, restricted, and 
classified — making it extremely difficult to 
train AI models for underwater object recognition.

PS3 Simulator solves this by generating 
physics-parametrised synthetic Side-Scan Sonar 
(SSS) images using Blender, then training 
I-JEPA — a structure-aware self-supervised 
learning framework — purely on synthetic data.

These weights are the result of that training.

---

## Available Weights

| File | Model | Pretrain | Epochs |
|------|-------|----------|--------|
| `jepa-ep200.pth.tar` | I-JEPA ViT-S/16 | PS3 Synthetic | 200 |
| `dino_ps3_checkpoint.pth` | DINO ViT-S/16 | PS3 Synthetic | 200 |

---

## Results on Real Sonar

Train: Synthetic PS3 only | Test: 876 real KSLG/SCTD images

| Model | Acc (%) | ±Std | F1 |
|-------|---------|------|-----|
| Random Init | 23.0 | ±0.9 | 0.239 |
| DINO PS3 (this repo) | 58.8 | ±11.9 | 0.639 |
| **I-JEPA PS3 (this repo)** | **70.9** | **±4.5** | **0.733** |
| DINO ImageNet | 78.8 | ±0.9 | 0.810 |
| I-JEPA ImageNet ViT-H† | 86.0 | ±0.1 | 0.796 |

†Upper bound — larger backbone, not directly comparable

---

## Usage

### Download weights

```python
from huggingface_hub import hf_hub_download
import torch

# I-JEPA ViT-S/16 pretrained on PS3
path = hf_hub_download(
    repo_id="kamalbasha/ps3-simulator",
    filename="jepa-ep200.pth.tar")

ckpt = torch.load(path, map_location='cpu')
print(ckpt.keys())
# ['target_encoder', 'encoder', 'predictor', ...]
```

### Load I-JEPA backbone

```python
import timm
import torch
from huggingface_hub import hf_hub_download

# Download weights
path = hf_hub_download(
    repo_id="kamalbasha/ps3-simulator",
    filename="jepa-ep200.pth.tar")

# Load backbone
backbone = timm.create_model(
    'vit_small_patch16_224',
    pretrained=False,
    num_classes=0)

ckpt = torch.load(path, map_location='cpu')

# Use target_encoder (EMA stable encoder)
sd = {k.replace('module.', ''): v
      for k, v in ckpt['target_encoder'].items()}

# Fix pos_embed shape [1,196,384] -> [1,197,384]
if sd['pos_embed'].shape != backbone.pos_embed.shape:
    cls_pe = backbone.pos_embed[:, :1, :]
    sd['pos_embed'] = torch.cat(
        [cls_pe, sd['pos_embed']], dim=1)

backbone.load_state_dict(sd, strict=False)
backbone.eval()
print('I-JEPA PS3 backbone loaded.')
```

### Load DINO backbone

```python
import timm
import torch
from huggingface_hub import hf_hub_download

# Download weights
path = hf_hub_download(
    repo_id="kamalbasha/ps3-simulator",
    filename="dino_ps3_checkpoint.pth")

# Load backbone
backbone = timm.create_model(
    'vit_small_patch16_224',
    pretrained=False,
    num_classes=0)

ckpt = torch.load(path, map_location='cpu')
sd = {k.replace('module.', '').replace('backbone.', ''): v
      for k, v in ckpt['student'].items()}

backbone.load_state_dict(sd, strict=False)
backbone.eval()
print('DINO PS3 backbone loaded.')
```

### Full evaluation pipeline

```python
# Clone repo and run notebook
git clone https://github.com/bashakamal/ps3-simulator
cd ps3-simulator
pip install -r requirements.txt

# Open and run:
# stage3_evaluation/PS3_Stage2_Evaluation.ipynb
```

---

## Training Details

### I-JEPA Pretraining

```
Model    : ViT-S/16
Data     : 1,008 synthetic PS3 SSS images (unlabeled)
Epochs   : 200
Optimizer: AdamW
Config   : configs/sonar_vits16.yaml
```

### Fine-tuning Protocol

```
Backbone : I-JEPA pretrained ViT-S/16
Head     : LayerNorm → Linear(384,256) → GELU 
           → Dropout(0.1) → Linear(256,2)
lr       : 1e-4
Epochs   : 100 (early stopping, patience=20)
Data     : Labeled synthetic PS3 images
Test     : Real KSLG/SCTD sonar (never seen)
```

---

## PS3 Simulator Dataset

Physics-parametrised synthetic SSS dataset:

```
Images   : 1,008
Classes  : Ship, Plane
Altitude : 50m, 70m, 100m
Seabed   : Sand, Gravel
Angles   : Varied grazing angles
Metadata : Per-image JSON with physical params
```

Dataset: [coming soon]
GitHub: [github.com/bashakamal/ps3-simulator](https://github.com/bashakamal/ps3-simulator)

---

## Citation

```bibtex
@inproceedings{basha2026ps3,
  title     = {PS3 Simulator: Physics-Parametrised Synthetic 
               Sonar for Self-Supervised Sim-to-Real Transfer},
  author    = {Basha, Kamal S; Athira Nambiar},
  booktitle = {Proceedings of the IEEE/CVF Conference on 
               Computer Vision and Pattern Recognition 
               Workshops (MaCVi)},
  year      = {2026}
}
```

---

## Acknowledgements

- [I-JEPA](https://github.com/facebookresearch/ijepa) — Facebook Research
- [DINO](https://github.com/facebookresearch/dino) — Facebook Research
- [timm](https://github.com/huggingface/pytorch-image-models) — HuggingFace
- [Blender MCP](https://github.com/ahujasid/blender-mcp) — 3D generation
- [SeabedObjects-KLSG](https://github.com/mvaldenegro/marine-debris-fls-datasets)

---

## License

MIT License