Asem Melebari Sepehr Eskandari Kazem Dogaheh Mahta Moghaddam William R McDermott 20250916 tabular digital data Reston, VA U.S. Geological Survey https://doi.org/10.5066/P9COO865 These datasets were collected by a ground penetrating radar unit installed on small Uncrewed Aircraft Systems (sUAS). Data include the two-way travel time (TWTT) for the ground surface (distance between the snow-ground interface and sUAS) and the calculated snow depth. The snow depth TWTT is defined as the time duration in nanoseconds that the electromagnetic wave takes to travel from the air-snow interface, reflect from the snow-ground surface, and then reach the air-snow interface again. The snow-ground and snow-air interfaces were identified by the magnitude of returns through a surface detection algorithm. The TWTT value provided in the dataset is a function of the snow depth and the radar wave velocity in the snow, which can be calculated from the snowpack density and the volumetric liquid water content in the snowpack. The sUAS based Software-defined Radar (SDRadar) data were collected during the snow-on-field campaigns in tandem with manual discrete snowpack measurements at Berthoud and Coal Bank Passes in Colorado, 2022-25. More information regarding the sUAS system used and data collection methods can be found in each metadata file Supplemental Information section for each data collection effort. The purpose of the dataset is to evaluate the accuracy of spatially distributed snow depth measurements calculated from sUAS based SDRadar TWTT data. The SDRadar data have the potential to improve snow depth monitoring over remote and complex terrain, which could improve water resource planning and modelling. These data are related to four cross referenced sources (McDermott and others, 2023; Bauer and others, 2023; Moeser and others, 2024; Prager and others, 2022), all of which shared at least one data collection field campaign and were collocated spatially and temporally. The University of Southern California (USC), Viterbi School of Engineering was awarded a Cooperative Ecosystems Studies Unit Federal Grant to build the sUAS SDRadar system. USC also processed the derived data for this effort. 20220315 20220418 20240409 20250408 ground condition Complete None planned -107.7886 -105.7635 39.8189 37.7332 None Radar TWTT SDRadar sUAS Bare Earth Horizon Snow Snow Depth Snow Water Equivalent DJI M600 USGS Metadata Identifier USGS:63853e37d34ed907bf77994f Places Colorado Coal Bank Pass Durango Silverton Colorado River Berthoud PAss None. Please see 'Distribution Info' for details. None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. These data are marked with a Creative Common CC0 1.0 Universal License. These data are in the public domain and do not have any use constraints Asem Melebari University of Southern California, Viterbi School of Engineering mailing

Denney Research Center (DRB), Suite 226

Los Angeles California 90089 United States (213) 740 2574 melebari@usc.edu USC Viterbi School of Engineering; U.S. Geological Survey Next Gerneration Water Observing Systems (NGWOS) Please contact the Dataset Point of Contact for more information on the computer operating systems and softwares used for data processing. William R. Mcdermott Graham A. Sexstone Colin A. Penn Tyler D. Lampard Duncan B. Morel Jon M. Gholson Joel W. Homan Evan J. Gohring Garrett A. Akie Andrea L. Creighton Erin K. Hennessy Nicholas G. Hall 2023 dataset Reston, VA U.S. Geological Survey https://doi.org/10.5066/p9nu5pv8 Mark A. Bauer Matthew A. Burgess Josip D. Adams Graham A. Sexstone John W. Fulton William R. Mcdermott Lance R. Brady 2023 dataset Reston, VA U.S. Geological Survey https://doi.org/10.5066/p9lf15ae Charles D. Moeser Jake C. Kurzweil William R. Mcdermott Tyler D. Lampard 2024 dataset Reston, VA U.S. Geological Survey https://doi.org/10.5066/p1eagt6y Samuel Prager Graham Sexstone Daniel McGrath John Fulton Mahta Moghaddam 2022 publication IEEE Transactions on Geoscience and Remote Sensing v. 60 n/a Institute of Electrical and Electronics Engineers (IEEE) p. 1-16 https://doi.org/10.1109/TGRS.2021.3117509 Please refer to individual data collection effort metadata files for accuracy report information. Data fall within expected ranges. There are no duplications or omissions, and data are logically consistent. Data are complete. Please refer to individual data collection effort metadata files for accuracy report information. Please refer to individual data collection effort metadata files for accuracy report information. Please see individual field campaign metadata files for process steps. 2025 Universal Transverse Mercator 13 1 -105 0 500000 0 coordinate pair 0.6096 0.6096 meters North American Datum of 1983 (NAD 83) 2011 epoch 2010.00 Geographic Reference System 1980 6378137.0 298.257222101 North American Vertical Datum of 1988 0.05 meters Explicit elevation coordinate included with horizontal coordinates BerthoudPass_20220315_USRP.zip Compressed (.zip) folder containing a metadata file and corresponding data file for TWTT in snow derived from sUAS based SDRadar collected on a Universal Software Radio Peripheral (USRP) system at Berthoud Pass, Colorado on March 15, 2022. Producer Defined BerthoudPass_20220418_USRP.zip Compressed (.zip) folder containing a metadata file and corresponding data files for TWTT in snow derived from sUAS based SDRadar collected on a Universal Software Radio Peripheral (USRP) system at Berthoud Pass, Colorado on April 18, 2022. Producer Defined CoalBankPass_20240409_USRP.zip Compressed (.zip) folder containing a metadata file and corresponding data files for TWTT in snow derived from sUAS based SDRadar collected on a Universal Software Radio Peripheral (USRP) system at Coal Bank Pass, Colorado on April 9, 2024. Producer Defined CoalBankPass_20240409_RFSoC.zip Compressed (.zip) folder containing a metadata file and corresponding data files for TWTT in snow derived from sUAS based Radio Frequency System on a Chip (RFSoC) SDRadar collected at Coal Bank Pass, Colorado on April 9, 2024. Producer Defined BerthoudPass_20250408_RFSoC.zip Compressed (.zip) folder containing a metadata file and corresponding data file for TWTT in snow derived from sUAS based RFSoC SDRadar collected at Berthoud Pass, Colorado on April 8, 2025. Producer Defined Five compressed (.zip) folders, each containing a metadata file and corresponding data files for TWTT in snow derived from sUAS based SDRadar in the Colorado Rocky Mountains, 2022-25. Melebari, A., Eskandari, S., Dogaheh, K., Moghaddam, M., and McDermott, W.R., 2025, Two-way Travel Time (TWTT) In Snowpack Derived from Software-defined Radar Data Collected by Small, Uncrewed Aircraft Systems (sUAS) in Colorado, 2022–25: U.S. Geological Survey data release, https://doi.org/10.5066/P9COO865. GS ScienceBase U.S. Geological Survey mailing address

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Digital Data https://doi.org/10.5066/P9COO865 None 20250916 William R McDermott U.S. Geological Survey, ROCKY MOUNTAIN REGION Physical Scientist mailing

Mail Stop 415, W 6th Ave Kipling St

Lakewood Colorado 80225 US 303-236-6886 wmcdermott@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998