Dear Colleagues,

The Earth’s surface is shaped by complex geomorphological processes and the interplay between endogenous and exogenous forces. As a consequence, landforms and landscapes archive information about the environmental conditions and geological processes and dynamics that created and transformed them over time. At the same time, gravity-driven, terrain-following mass flows (e.g. water, debris and mud flows, landslides, lava flows, pyroclastic density currents), which can threaten human life and property, as well as infrastructure, are largely controlled by topography. Therefore, topographic data, mainly in the form of Digital Elevation Models (DEMs), have been widely generated and applied throughout essentially all geosciences. Various active and passive sensing techniques have been developed for producing DEM data, which include but are not limited to: stereo- and multi-view photogrammetry, light detection and ranging (LiDAR), and interferometric synthetic aperture radar (InSAR).

Recently, unmanned aerial vehicles (UAVs), more colloquially referred to as “drones”, have emerged as a new, efficient, and low-cost platform to facilitate topographic data acquisition. UAVs’ flexibility of operation, the capability of flying below layers of clouds, and its capacity of overflying large areas in relatively short time make UAV-mounted sensors systems an outstanding method for digital terrain modeling. The high spatio-temporal resolutions of resulting DEMs allow for improvement of existing methodologies and development of new ones to better integrate topography, morphology, and morphogenetic processes at a wide range of spatio-temporal scales. This significantly improves our means of monitoring, analyzing, and understanding the dynamics of Earth’s surface changes.

Contributions may include, but are not limited to:

• Technical advances of UAV systems and sensors that facilitate topographic data acquisition more efficiently and at unprecedented detail and quality.
• Innovative integration of different data sources, such as optical cameras, GNSS sensors, and LiDAR systems, resulting in advanced data products.
• Guidelines, recommendations and best practices regarding UAV surveys and data collection that have proved to perform well and produce optimal raw-data density, data point distribution and relative location accuracy.
• New or improved DEM data processing methods and techniques, such as optimized Structure from Motion (SfM) algorithms and improved performance of other computer vision approaches.
• Accuracy analyses and error assessments of UAV-acquired data and derived DEMs, including error detection, quantification, and propagation, as well as the comparison of different surface reconstruction methods.
• Geomorphological mapping and morphometric analysis of landforms and landscapes based on UAV-derived DEMs, with particular emphasis on the advantages of high spatio-temporal DEM resolutions for the detection of topographic features and changes on very fine scales.
• Topographic change detection and quantification by differentiating pre-, co-, and post-event UAV-derived DEMs aimed to quantify the volume added or removed by Earth surface processes as well as to improve the comprehension of their transport and emplacement mechanism.
• Advancement in understanding the role of topography in the transport and emplacement mechanisms of gravity-driven flows and the resulting morphologies.
• Advancement in the hazard assessment and management of hazardous phenomena (flooding, debris and mud flows, landslide, lava flow, and pyroclastic density current, etc.) thanks to the availability of UAV-based rapid and low-cost topographic updates and progresses in monitoring such phenomena through almost real-time topographic reconstruction.
• Improvement in the computer modeling of gravity-driven flows resulting from the increase in the spatio-temporal resolution of UAV-derived topographic data.

Dr. Alessandro Fornaciai
Dr. Nicole Richter
Mr. Massimiliano Favalli
Mr. Luca Nannipieri
Guest Editors

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• Unmanned Aerial Vehicles
• Topographic mapping and change detection
• Structure from Motion
• Digital Terrain Modeling
• Digital Elevation Models
• Topography
• Landscape evolution
• Earth's surface processes
• Geomorphometry