From Digital Earth to big Earth data: accelerating scientific discovery and supporting global sustainable development

Since the advent of Digital Earth concept 20 years ago, the relevant theories and technologies have developed so quickly and great achievements have been made. Through collecting and processing the massive, multi-spatial, multi-temporal, and multi-dimension Earth observation and socioeconomic data as well as formulating algorithms and models, Digital Earth serves as a good platform to help people better understand the planet we are living on. With the revolutionary innovation of big data, many new methods in scientific research have been developed. Big data encourages a new way of thinking about and seeking for new discoveries about the world. When this new method is combined with the research of Earth sciences, big Earth data began to show its role in the knowledge discovery and supporting national and global strategies. Big Earth data, to a certain degree, is a new developing stage of Digital Earth. Big Earth data stands for all the data related to the Earth science, not only limited to Earth-observing data. It consists of data related to the Earth’s interior, surface, atmosphere, and near-space environment and is characterized as being multi-source, heterogeneous, multi-temporal, multi-scalar, highly dimensional, highly complex, nonstationary, unstructured, and so on. Big Earth data not only provides technical computing resolution on the Earth-related data but also owns the macrolevel capabilities of enabling rapid and accurate monitoring of the Earth system, both of which pave ways to significant scientific discoveries of the Earth. Big Earth data is at the forefront of the integration of Earth science, information science, and space science and technologies. By supporting the data-intensive research in the Earth sciences, big Earth data becomes a new engine of knowledge innovation in the Earth sciences, and provides new resolution for meeting the global challenges through realizing the initiatives, including the UN Sustainable Development Goals (SDGs), Paris Agreement on climate change, and Sendai Framework on disaster risk. The Chinese Academy of Sciences has established a program named Big Earth Data Science Engineering (CASEarth) to contribute the realization of some SDGs. With the deeper research and development of big Earth data, an accountable, measurable, and predictable future could be expected. On this basis, IJDE will publish papers using big Earth data technologies to resolve some problems humans are concerning about. In this issue, six papers are included. Four papers focus on urban studies from different research angles, one paper talks about extracting spatio-temporal data from social media based on ontology-based method, and the other paper reviews the methods of using ground-penetrating radar to measure soil water. Hope you enjoy these papers and keep focusing on the following publications of IJDE.