Ground control point locations and topographic GNSS measurements collected during the UAS survey of the debris flow at South Fork Campground, Sequoia National Park, CA

This portion of the data release presents topographic Global Navigation Satellite System (GNSS) measurements acquired during the UAS survey of the debris flow at South Fork Campground in Sequoia National Park. The data contain the locations of the temporary ground control points (GCPs) used for the structure-from-motion (SfM) processing, as well as topographic measurements collected using a backpack-mounted GNSS rover. For the GCPs, 23 temporary points consisting of a combination of small square tarps with black-and-white cross patterns and "X" marks placed on the ground using temporary chalk were distributed throughout the survey area. For each GCP measurement the GPS receiver was placed on a fixed-height tripod and set to occupy the GCP for a minimum occupation time of one minute. For the topographic data acquisition, a GNSS rover was mounted to a backpack and used to collect continuous 1-second data on bare-ground surfaces of the debris flow site that were accessible on foot. The GNSS measurements were made using a real-time kinematic (RTK) GPS, with corrections from a GPS base station located on a temporary benchmark ("SFKW") established on the foot of the debris flow. The approximate base station position was initially derived using an autonomous position. The final coordinates for SFKW were derived using a seven-hour static occupation, submitted to the National Geodetic Survey Online User Positioning Service (OPUS-S). The resulting OPUS solution conforms to the quality standards for a USGS Level II single-base survey. After the survey was completed, the RTK data were adjusted using the final SFKW position using the Trimble Business Center software package. The GNSS data are presented in a comma-delimited text file.