DOI: 10.5880/gfz.2.1.2020.001
title: High-resolution photogrammetry data of the Santiaguito lava dome collected by UAS surveys

description: Imaging growing lava domes has remained a great challenge in volcanology due to their inaccessibility and the severe hazard of collapse or explosion. Here, we present orthophotos and topography data derived from a series of repeated survey flights with both optical and thermal cameras at the Caliente lava dome, part of the Santiaguito complex at Santa Maria volcano, Guatemala, using an Unoccupied Aircraft System (UAS). The data archived here supplements the material detailed in Zorn et al. (2020, https://doi.org/10.1038/s41598-020-65386-2). Note, all files are saved in WGS 84 / UTM Zone 15N format. The data are provided the following .zip folders:- 2020-001_Zorn-et-al_DEM-Geotiffs-zip: DEMs of surveys A-D in geotiff format (.tif)- 2020-001_Zorn-et-al_Orthophotos.zip: Orthophotos of surveys A-D and 2 thermal surveys as Tiff-images (.tif). A .jpg of the color scale for the thermal data is also included- 2020-001_Zorn-et-al_Point_Cloud_Models.zip: Point clouds of surveys A-D, 2 thermal surveys (.las)
description: During fieldwork in February 2019 we performed UAS survey flights over the active Caliente vent at Santiaguito volcano with multiple drones and sensors at a height of approx. 100 m over the lava dome (Fig. 1a, 2a). The flights were recorded using high-resolution optical photos and an additional thermal camera. The optical images were acquired with the onboard sRGB camera of our UAS (DJI Phantom 4 Pro) with a resolution of 5472 x 3078 px and a sampling rate of 0.5 Hz. The thermal images were acquired with a FLIR TAU 2 (9 mm lens), stored in a TEAX ThermalCapture frame grabber, and processed with the Thermoviewer software (v3.0.4). These provided radiometric temperature data and had a resolution of 640 x 512 px with a sampling rate of 8 Hz. In total we processed four flights with optical photos (named surveys A, B, C, and D) and two thermal flights. We performed Structure-from-Motion (SfM) photogrammetric processing using Agisoft Metashape 1.5.2 on all optical and thermal surveys to reconstruct the 3D environment of the active lava dome, enabling us to construct both high resolution DEMs from dense point clouds as well as detailed orthophotos. The survey photos were acquired in nadir or near-nadir position, with only some single photos being taken at an oblique angle to improve the model quality. The difficult and hazardous terrain did not allow for sufficient ground control points to create a reliable georeferencing. To georeference the UAS datasets acquired at Santiaguito volcano, we used a photogrammetric model built from high-resolution optical Pléiades satellite imagery on 15.01.2017. In this process, the SfM-built DEM is attached to the Pléiades one by identifying recognizable features in both datasets. The final referencing had an RMS-error of 3.3 m, but due to the high resolution of the SfM models, they could be better referenced relative to each other, meaning that all other SfM-DEMs now use the prereferenced Survey D as a basis. This minimizes the relative errors between the DEMs and allows for high-precision data comparison. Here, all models are within 0.3 m accurate relative to each other.