Simulating Your First Operational Risk#

Real-world deployments expose AI models to environmental and sensor-level degradations that rarely appear in training data. Validating robustness to these conditions is a core part of Artificial Intelligence Test & Evaluation (AI T&E).

In this guide, you’ll use NRTK’s JitterPerturber to apply a physics-based jitter perturbation that simulates high-frequency vibration — the kind of sensor blur caused by wind, vehicle movement, or mechanical instability on mounted cameras. By the end, you’ll be able to:

  • Understand what an operational risk perturbation looks like in practice

  • See how a few lines of code can simulate a real-world degradation

  • Get a feel for NRTK’s perturbation workflow before exploring more perturbers

When to Use This#

  • You want to simulate platform vibration from wind, vehicle movement, or mechanical instability.

  • You need a physics-based perturbation that models realistic motion blur effects.

  • You’re doing early screening of robustness to vibration before running heavier T&E analysis (see the full T&E Simulation Guide → JitterPerturber T&E guide).

  • You want to test model performance at reduced effective resolution due to motion.

Example: Jitter Perturbation#

Important

JitterPerturber requires the pybsm extra. If you haven’t already, install it:

pip install nrtk[pybsm]

See Installation for alternatives.

The following example loads an image, applies a jitter perturbation, and saves the result:

from nrtk.impls.perturb_image.optical.otf import JitterPerturber
import numpy as np
from PIL import Image

# Load your image
image = np.array(Image.open("your_image.jpg"))

# Apply jitter perturbation
# img_gsd = ground sample distance (meters/pixel) for your sensor
perturber = JitterPerturber(s_x=8e-6, s_y=8e-6)
perturbed_image, _ = perturber(image=image, img_gsd=0.03)

# Save the result
Image.fromarray(perturbed_image).save("perturbed_output.jpg")

The s_x and s_y parameters control jitter amplitude — see Key Parameters below for details and visual comparisons.

Here’s what the perturbation looks like in practice:

Baseline Image (No Jitter)

Image with Simulated Sensor Jitter
../_images/input.jpg ../_images/output-jitter.jpg

Notice how the jitter perturbation introduces motion blur that reduces edge sharpness and suppresses fine detail. In deployed systems, this kind of degradation can increase missed detections, reduce confidence scores, and lower mAP — precisely the kinds of robustness gaps T&E aims to surface before fielding. The severity of this degradation is controlled by the jitter amplitude parameters, explored below.

Key Parameters#

  • s_x, s_y — Root-mean-squared jitter amplitudes in x and y directions (radians). These represent the standard deviation of angular positional error due to platform vibration. Larger values produce a stronger Gaussian blur.

    Light (0, 3e-4)

    Medium (0, 5e-4)

    Heavy (0, 1e-3)
    ../_images/jitter_light.png ../_images/jitter_medium.png ../_images/jitter_heavy.png

See also

For a deeper dive into optical perturber parameters and OTF modeling, see the Optical Perturbers notebook.

Other Operational Risks#

NRTK provides perturbers for a range of real-world degradations beyond vibration. Each module below includes a description, code example, parameter comparison, and links to further resources.

🌫️ Haze

Simulates reduced visibility from fog, mist, or light snow.

Haze Simulation Module
🌀 Atmospheric Turbulence

Simulates blur and distortion from unstable air masses.

Atmospheric Turbulence Simulation Module
☀️ Extreme Illumination

Simulates under- or overexposure from harsh lighting conditions.

Extreme Illumination Simulation Module
🔍 Target Out of Focus

Simulates optical defocus from autofocus failures or focus errors.

Target Out of Focus Simulation Module
🔭 Radial Distortion

Simulates barrel or pincushion distortion from wide-angle lenses.

Radial Distortion Simulation Module
📡 Sensor Noise & Resolution

Simulates thermal noise, electronic noise, and resolution loss.

Sensor Noise and Resolution Effects Simulation Module
💧 Water Droplets

Simulates lens contamination from rain or water spray.

Water Droplets Simulation Module

References#