
Object Recognition in Atmospheric Turbulence
Scenes
Disen Hu
Visual Information Laboratory
University of Bristol
Bristol, UK
zr18100@bristol.ac.uk
Nantheera Anantrasirichai
Visual Information Laboratory
University of Bristol
Bristol, UK
n.anantrasirichai@bristol.ac.uk
Abstract—The influence of atmospheric turbulence on acquired
surveillance imagery poses significant challenges in image in-
terpretation and scene analysis. Conventional approaches for
target classification and tracking are less effective under such
conditions. While deep-learning-based object detection methods
have shown great success in normal conditions, they cannot be
directly applied to atmospheric turbulence sequences. In this
paper, we propose a novel framework that learns distorted
features to detect and classify object types in turbulent environ-
ments. Specifically, we utilise deformable convolutions to handle
spatial turbulent displacement. Features are extracted using a
feature pyramid network, and Faster R-CNN is employed as
the object detector. Experimental results on a synthetic VOC
dataset demonstrate that the proposed framework outperforms
the benchmark with a mean Average Precision (mAP) score
exceeding 30%. Additionally, subjective results on real data show
significant improvement in performance.
Index Terms—atmospheric turbulence, object detection, deep
learning, deformable convolution, object recognition
I. INTRODUCTION
Atmospheric turbulence consistently degrades visual quality
and has a negative impact on the performance of automated
target recognition and tracking in a scene. These distortions oc-
cur when there is a temperature difference between the ground
and the air, causing rapid upward movement of air layers and
resulting in changes to the interference pattern of light refrac-
tion. This leads to visible ripples and waves in both spatial
and temporal directions in images and videos. Mitigating this
effect is an ill-posed problem with non-stationary distortions
varying across time and space, and a degree of distortions is
unknown. The restoration process is thus complex and time-
consuming. Objects behind the distorting layers are almost
impossible to recognise by machines leading to a failure
of automatic detection and tracking processes. Examples of
applications directly affected with atmospheric turbulence are
video surveillance, security and defence.
Object detection methods on natural and clean images have
been greatly developed achieving high performance in term of
both detection accuracy and computational speed. The state of
the arts are based on deep learning with convolutional neural
networks (CNN) (see recent techniques for object detection
This work was supported by the UKRI MyWorld Strength in Places
Programme (SIPF00006/1).
in [1]). However, the performance of these methods declines
when the features are corrupted by noise or distorted by blur.
This degradation is even more pronounced in the case of at-
mospheric turbulence, where distortions appear randomly and
are spatially and temporally invariant [2]. Up to now, only face
recognition in atmospheric turbulence has been developed [3].
They have also proved that training deblurring and detection
models together gives better results than separating the models.
In this paper, we tackle the multi-class object detection
in atmospheric turbulence scenes without image restoration
process. Our framework is hence fast and straightforward. The
method is developed based on the Faster R-CNN detector [4],
but this should not be limited to. The features are extracted
with a feature pyramid network (FPN) [5], which can deal
with different resolutions, different sizes of the objects, and
different amounts of distortions. To mitigate the effects of at-
mospheric turbulence, we incorporate deformable convolutions
[6], which help reduce the impact of visible ripples along ob-
ject edges caused by atmospheric turbulence. A key contribu-
tion is that, as in the atmospheric turbulent environments, the
objects exhibit visual distortions within small ranges of pixel
displacement appearing randomly at all directions. The use
of deformable convolutions provides flexibility in capturing
the shapes of the objects and assists the FPN in extracting
the appropriate features from the distorted objects. As there
is no ground truth available for this problem, we trained the
model using a synthetic dataset and evaluated its performance
using both synthetic and real datasets. Our code is available
at https://github.com/disen-hu/FasterRcnn FPN DCN.
II. RELATED WORK
Image restoration techniques for atmospheric turbulence
have been extensively studied [7]–[9], with some methods
specifically addressing moving objects in distorted scenes [2],
[10]–[12]. Deep learning technologies have also gained atten-
tion in atmospheric turbulence mitigation, although they are
still in the early stages of development. Existing architectures
have been employed and retrained using synthetic datasets in
various methods [13]–[15]. Additionally, the use of Complex-
Valued CNN was explored in [16], demonstrating significant
improvements over traditional CNN-based approaches.
arXiv:2210.14318v2 [cs.CV] 29 May 2023