A typical assumption for deploying machine learning models is that the model training and inference data were drawn from the same distribution. However, this assumption rarely holds true for systems deployed in the open world. Inference data can drift over time for numerous reasons, such as changes in operating conditions, adversarial modifications to targets, or sensor degradation. Despite these changes, deep learning models are especially vulnerable to issuing over-confident predictions on out-of-distribution data. This work seeks to address this issue by proposing a framework for describing out-of-distribution detection pipelines, proposing an out-of-distribution detection algorithm using Gaussian Mixture Models which is well suited for SAR ATR, and by evaluating multiple pipelines which exploit the intermediate states of ATR model deep neural networks. This work studies candidate pipelines with varied amounts of dimensionality reduction and detection algorithms on the SAMPLE+ dataset challenge problems for clutter and confuser rejection. Despite the exclusion of out-of-distribution samples from pipeline training, the presented results demonstrate that these samples can nonetheless be reliably detected, exceeding baseline performance by more than 10 percentage points.
Synthetic data is commonly used to assess the performance of Synthetic Aperture Radar (SAR) Automatic Target Recognition (ATR) systems modeling the OC space in question. In this work we demonstrate that the use of an informed sampling technique compared to an uninformed sampling approach can efficiently assess the “OC gap” between train and test OC spaces as the gap narrows. To demonstrate the effectiveness of an informed sampling approach, SAR ATR experiments are conducted as a function of how representative the train distribution of OCs are compared to the test OC space given a variety of challenging OC scenarios. Algorithm performance is assessed over a series of experiments given discrepancies between azimuth and depression angle of the sensor.
Synthetic data is often leveraged for training and testing Automatic Target Recognition (ATR) systems on a variety of operating conditions (OCs). Existing mechanisms for creating the sampling distribution of OCs to generate this data are difficult to visualize, modify, and extend. To address this, we created a user interface and toolchain for multi-modal OC sampling from probabilistic graphical models (PGMs). Our web browser-based interface allows for visualizing the PGMs, modifying the conditional probability distributions of their nodes, importing and exporting their state, operation in single- or multi-modality configurations, and persisting generated samples to a relational database. The Vue-driven web interface, programmatic interface, as well as the Python machinery for OC sampling and persistence have been containerized to allow for simplified deployment and distribution. The work described here supplies a new baseline for OC generation for single- and multi-sensor simulation and fusion.
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