**Preface to "UAVs for Vegetation Monitoring"**

Global plant production faces the major challenge of sustainability under the constraint of a rapidly growing world population and the gradual depletion of natural resources. Remote sensing can play a fundamental role in changing the production model through the development and implementation of new technologies for vegetation monitoring (e.g., advanced sensors and remote platforms, powerful algorithms, etc.) that will lead to higher yields and more sustainable and environmentally friendly food and plant products. Unmanned aerial vehicles (UAVs) or drones have been highlighted as one of the most suitable tools for timely tracking and assessment of vegetation status. They can operate at low altitudes, providing an ultra-high spatial resolution image, have great flexibility of flight schedules for data collection at critical and desired moments, and, also, the generation of digital surface models (DSMs) using highly overlapped images and photo-reconstruction techniques or artificial vision. Therefore, it is essential to advance the research for the technical configuration of UAVs, as well as to improve processing and analysis of the UAV imagery of agricultural and forest scenarios in order to strengthen the knowledge of ecosystems and thereby improve farmers' decision-making processes.

This book compiles a set of original and innovative papers included in the Special Issue on UAVs for vegetation monitoring, which proposes new methods and techniques applied to diverse agricultural and forestry scenarios. It is addressed to all members involved in the development and applications of UAVs on vegetation.

The editors of this book would like to thank the authors for selecting this special issue to publish their most recent findings, as well as the editor team members for their help in this process.

> **Ana I. de Castro, Yeyin Shi, Joe Maja, Jose M. Pe ˜na** *Editors*
