Being a cornerstone of temporal analysis, change detection has been playing a pivotal role in modern earth observation. Existing change detection methods rely on the Siamese encoder to individually extract temporal features followed by temporal fusion. Subsequently, these methods design sophisticated decoders to improve the change detection performance without taking into consideration the complexity of the model. These aforementioned issues intensify the overall computational cost as well as the network's complexity which is undesirable. Alternatively, few methods utilize the early fusion scheme to combine the temporal images. These methods prevent the extra overhead of Siamese encoder, however, they also rely on sophisticated decoders for better performance. In addition, these methods demonstrate inferior performance as compared to late fusion based methods. To bridge these gaps, we introduce encoder only change detection (EoCD) that is a simple and effective method for the change detection task. The proposed method performs the early fusion of the temporal data and replaces the decoder with a parameter-free multiscale feature fusion module thereby significantly reducing the overall complexity of the model. EoCD demonstrate the optimal balance between the change detection performance and the prediction speed across a variety of encoder architectures. Additionally, EoCD demonstrate that the performance of the model is predominantly dependent on the encoder network, making the decoder an additional component. Extensive experimentation on four challenging change detection datasets reveals the effectiveness of the proposed method.

翻译：作为时间分析的基石，变化检测在现代地球观测中发挥着关键作用。现有变化检测方法依赖孪生编码器分别提取时序特征后进行时序融合。随后，这些方法设计复杂的解码器以提升变化检测性能，却未充分考虑模型复杂度。上述问题加剧了整体计算成本与网络复杂性，这是不可取的。少数方法采用早期融合方案合并时序图像，虽避免了孪生编码器的额外开销，但仍依赖复杂解码器以获得更好性能。此外，与基于晚期融合的方法相比，这些方法表现出较差的性能。为弥补这些不足，我们提出仅编码器变化检测（EoCD），这是一种简单有效的变化检测方法。该方法对时序数据进行早期融合，并用无参数多尺度特征融合模块替代解码器，从而显著降低模型整体复杂度。EoCD在多种编码器架构中实现了变化检测性能与预测速度的最佳平衡。此外，EoCD证明模型性能主要取决于编码器网络，解码器仅作为附加组件。在四个具有挑战性的变化检测数据集上的大量实验验证了所提方法的有效性。