UAS-based very high resolution digital elevation model and orthomosaic of the lower Pica Valley, Atacama Desert

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Main Title: UAS-based very high resolution digital elevation model and orthomosaic of the lower Pica Valley, Atacama Desert

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Abstract: This dataset contains a very high resolution (<10 cm) digital elevation model (DEM) and orthomosaic (OM) covering a section of the lower Pica Valley in northern Chile (20.44°S/69.2°W). DEMs and OMs are based on aerial imagery acquired with a low-cost unmanned aerial system (UAS) on two flight missions conducted on the 3rd of April 2018. Both missions were carried out in a double grid network with 75% frontal image overlap, a nominal flight height of 150 m above the starting point, and a nominal camera angle of 10°. For subsequent structure-from-motion (SfM) and multi-view stereo (MVS) processing we used the software Agisoft Metashape Pro 1.6.3.10732. After initial removal of blurry images using a software-internal image quality threshold of 0.75, in total 388 images were processed following the workflow after USGS (2017), adapted according to James et al. (2020), and further described by Walk et al. (2022). Photo alignment was carried out in highest quality. Uniform accuracy values for camera location and angle of 10 m and 10°, respectively, as well as a marker measurement accuracy of 5 cm were set. An iterative filtering of the sparse point cloud and subsequent optimization of photo alignment was applied based on the reconstruction uncertainty (≤50) and projection accuracy (≤5). Without adding any ground control, photo alignment was then optimized following iterative exclusion of points with a reprojection error >0.3 (USGS, 2017). In all steps, adapted lens distortion parameters covered f, Cx, Cy, B1, B2, K1, K2, K3, K4, P1, and P2. Due to the reasons elaborated by James et al. (2020), the marker accuracy for image coordinates was set to 0.1 pix and the tie point accuracy was adapted iteratively by optimizing the photo alignment to a value of 0.137 until a standard error of unit weight of 1.00 is reached. Precision estimates of the sparse point cloud were calculated using the Python script provided by James et al. (2020). Based on a dense cloud computed under high quality settings, a DEM with a spatial resolution of 9.2 cm was constructed, which, in turn, was used to compute an orthomosaic with a spatial resolution of 4.6 cm. The raster geodata is stored in GeoTIFF format and the processing report by Agisoft is provided as a .pdf document. Additionally, photogrammetric processing results for cameras and tie points, and the sparse point cloud precision estimates are provided as .txt files.
Other: James, M.R., Antoniazza, G., Robson, S., Lane, S.N., 2020. Mitigating systematic error in topographic models for geomorphic change detection: accuracy, precision and considerations beyond off-nadir imagery. Earth Surface Processes and Landforms 45, 2251–2271. https://doi.org/10.1002/esp.4878; United States Geological Survey, 2017. Unmanned aircraft systems data postprocessing: structure-from-motion photogrammetry (USGS). Section 2 – MicaSense 5-band MultiSpectral Imagery. USGS National UAS Project Office. Retrieved: https://uas.usgs.gov/nupo/pdf/PhotoScanProcessingMicaSenseMar2017.pdf. (Accessed 24 July 2020); Walk, J., Bartz, M., Stauch, G., Binnie, A., Brückner, H., Lehmkuhl, F., 2022. Weathering under coastal hyperaridity – Late Quaternary development of spec-tral, textural, and gravelometric alluvial fan surface characteristics. Quaternary Science Reviews 277, 107339. https://doi.org/10.1016/j.quascirev.2021.107339

Responsible Party

*Creator:*	Janek Walk (Author)
*Funding Reference:*	Deutsche Forschungsgemeinschaft (DFG): CRC 1211: Earth - Evolution at the Dry Limit
*Publisher:*	CRC1211 Database (CRC1211DB)
*Publication Year:*	2022

Topic

*CRC1211 Topic:*	Surface
*Related Subproject:*	C2
*Subjects:*	Keywords: Ground-based remote sensing, Geomorphology, GIS
*Geogr. Information Topic:*	Environment

File Details

*Filename:*	PICA_UAS_SfM_MVS_DEM_OM_v0322.zip
*Data Type:*	Dataset - Raster geodata
*Size:*	2 Datasets
*File Size:*	1.2 GB
*Date:*	Created: 30.03.2022
*Mime Type:*	application/zip
*Data Format:*	GeoTIFF
*Language:*	English
*Status:*	Completed

Constraints

*Download Permission:*	Only Project Members
*General Access and Use Conditions:*	According to the CRC1211DB data policy agreement.
*Access Limitations:*	According to the CRC1211DB data policy agreement.
*Licence:*	[CRC1211DB] Data policy agreement

Geographic

Specific Information - Data

*Temporal Extent:*	03.04.2018
*Lineage:*	Coordinate system: WGS 1984 / UTM zone 19S (32719); Vertical DEM reference: mean sea level (orthometric heights); Spatial resolution (ground sampling distance) of DEM / OM [m]: 0.092 / 0.046
*Subtype:*	Geospatial Data
*Scope:*	Dataset
*Initiative Type:*	Study

Metadata Details

*Metadata Creator:*	Janek Walk
*Metadata Created:*	14.12.2022
*Metadata Last Updated:*	15.12.2022
*Subproject:*	C2
*Funding Phase:*	2
*Metadata Language:*	English
*Metadata Version:*	V50

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