**Preface to "Multi-Sensor Systems and Data Fusion in Remote Sensing"**

This book collects papers belonging to the Special Issue of MDPI Remote Sensing entitled "Multi-Sensor Systems and Data Fusion in Remote Sensing". The currently observed technological progress, including the emergence of new sensors, development of sophisticated platforms for those sensors, and advances in signal and data processing, creates an opportunity for scientists and engineers to develop new and more capable integrated multi-sensor systems. Extended frequency bands, improved resolutions, and data rates of the new sensors as well as the common use of distributed sensors increase the influx of data in contemporary multi-sensor systems. At the same time, the users' expectations with respect to the size of the observed area or volume, data resolution, accuracy, speed of operation, and functionality of remote sensing systems are still increasing. These facts pose new challenges for the data fusion algorithms that must often employ the newest achievements from the areas of big data mining, statistical estimation, artificial intelligence, etc. The presented material provides a fresh insight into the newest developments in the fields of multi-sensor systems and data fusion and will be of interest to the entire remote sensing community.

#### **Piotr Kaniewski, Mateusz Pasternak, and Stefano Mattoccia** *Editors*
