CADA-Net: cross-altitude domain-adaptive perception for label-efficient onboard sensing in autonomous UAVs

Autonomous unmanned aerial vehicles (UAVs) depend on onboard perception as the front end of their sensing-decision-control loop, where each detection feeds directly into the navigation, avoidance, and tracking decisions made in flight. Yet detectors trained at one altitude routinely degrade when the platform is redeployed at another, because the underlying distribution shift couples scale, viewpoint, and target density. This study addresses the cross-altitude transfer gap by proposing CADA-Net, an altitude-conditioned detector for onboard UAV perception that treats altitude as an exploitable domain variable rather than a nuisance to be removed. The framework injects a categorical altitude prior into multi-scale features through feature-wise linear modulation, aligns cross-altitude representations via a gradient-reversal adversarial discriminator attached to each pyramid level, and generates target-domain pseudo-supervision through a weak-to-strong teacher-student self-training stream, all sharing a single conditioned encoder. Together these components target not raw recognition accuracy alone but perception that remains stable as the platform's viewing geometry and object density change through flight. Evaluated on the UAVDT benchmark under a low → high adaptation protocol, CADA-Net reaches 46.3 mAP@0.5 on the high-altitude band, surpassing the source-only baseline by 17.9 points and the strongest domain-adaptive competitor by 7.2 points, while leaving only a 6.3-point gap to a fully-supervised upper bound; with 5% of target labels, accuracy rises to 48.1 mAP@0.5. Onboard profiling on a Jetson AGX Orin sustains 42 FPS at INT8 precision within a 27.4 W envelope, indicating that the accuracy gain survives the throughput and power limits of embedded inference, which is a precondition for onboard use rather than evidence of closed-loop flight. These findings indicate that rendering a geometric prior explicit can support label-efficient perception at embedded inference rates for UAV platforms operating across altitude transitions.