Imagine generating a city’s electricity demand pattern based on weather, the presence of an electric vehicle, and location, which could be used for capacity planning during a winter freeze. Such real-world time series are often enriched with paired heterogeneous contextual metadata (e.g., weather and location). Current approaches to time series generation often ignore this paired metadata. Additionally, the heterogeneity in metadata poses several practical challenges in adapting existing conditional generation approaches from the image, audio, and video domains to the time series domain. To address this gap, we introduce TIME WEAVER, a novel diffusion-based model that leverages the heterogeneous metadata in the form of categorical, continuous, and even time-variant variables to significantly improve time series generation. Additionally, we show that naive extensions of standard evaluation metrics from the image to the time series domain are insufficient. These metrics do not penalize conditional generation approaches for their poor specificity in reproducing the metadata-specific features in the generated time series. Thus, we innovate a novel evaluation metric that accurately captures the specificity of conditional generation and the realism of the generated time series. We show that TIME WEAVER outperforms state-of-the-art benchmarks, such as Generative Adversarial Networks (GANs), by up to 30% in downstream classification tasks on real-world energy, medical, air quality, and traffic datasets.

The rapid evolution of satellite imaging systems has resulted in sharp increases of image archive volumes. Multitemporal images constitute a sizeable portion of these time-series databases. Accordingly, development of accurate content based time-series retrieval (CBTSR) methods in massive archives of RS images attracts much research interest. Given a user-defined query time series, CBTSR aims at identifying within a massive archive image time series that show characteristics similar to those of the query time series. In this paper, we focus our attention to CBTSR in pairs of RS images, aiming to search and retrieve bi-temporal image pairs containing changes similar to those modeled in the query. To this end, we introduce two deep learning-based methods in the framework of CBTSR. The first method, called deep change vector retrieval (DVCR), is based on selected deep features extracted from the change vector analysis. The second method, called autoencoder with early fusion (AEEF) uses an autoencoder architecture to recreate the time difference images and the latent codes produced by this network. Experimental results show the effectiveness of the proposed methods for CBTSR problems. The code of the proposed methods is available at: https://github.com/OnatV/ChangeRetrieval.