Object Detector Differences When using Synthetic and Real Training Data

To train well-behaved generalizing neural networks, suffic iently large and diverse datasets are needed. Collecting data while adhering to privacy legislation becomes increasingly difficult and annotating these large datasets is both a resource-heavy and time-consuming task. An approach to overcome these difficulties is to use synthetic data since it is inherently scalable and can be utomatically annotated. However, how training on synthetic data affects the layers of a neural network is stil l unclear. In this paper, we train the YOLOv3 object detector on real and synthetic images from city environment s. We perform a similarity analysis using Centered Kernel Alignment (CKA) to explore the effects of train ing on synthetic data on a layer-wise basis. The analysis captures the architecture of the detector while sh owing both different and similar patterns between different models. With this similarity analysis we want to g ive insights on how training synthetic data affects each layer and to give a better understanding of the inner wor kings of complex neural networks. The results show that the largest similarity between a detector trained on real data and a detector trained on synthetic data was in the early layers, and the largest difference was in the head part.