Aerial imagery and structure-from-motion data products from a UAS survey of the Los Padres Reservoir delta, Carmel River valley, CA, 2017-11-01

An unoccupied aerial system (UAS) was used to acquire high-resolution imagery of the exposed reservoir delta at Los Padres Reservoir, in the Carmel River valley in central California on 1 November 2017. This survey followed sediment delivery to the reservoir by the Carmel River due to landscape response after the 2016 Soberanes Fire and high flows in winter 2017. The imagery from this survey was processed using structure-from-motion (SfM) photogrammetric techniques to derive a high-resolution digital surface model (DSM), a digital elevation model (DEM), an orthomosaic image, and a topographic point cloud.
 
A total of six flights were conducted for the survey between 19:35 and 22:15 UTC (12:35 and 15:15 PDT). Only the imagery from fights F03 and F06 were used for data processing and are included in this data release. All flights were conducted at an approximate altitude of 100 meters above ground level resulting in a nominal ground-sample-distance (GSD) of 2.6 centimeters per pixel.

The flights were conducted using a Department of Interior-owned 3DR Solo quadcopter fitted with a Ricoh GR II digital camera featuring a global shutter. The UAS was flown on pre-programmed autonomous flight lines which were spaced to provide approximately 70 percent overlap between images from adjacent lines. The camera shutter was triggered at 1 Hz using a built-in intervalometer. Before each flight, the camera’s digital ISO, aperture, and shutter speed were adjusted for ambient light conditions.

Twenty temporary ground control points (GCPs) consisting of small square tarps with black-and-white cross patterns were distributed throughout the area to establish survey control. The GCP positions were measured using real-time kinematic (RTK) GPS, using corrections from a GPS base station located on a benchmark designated SFML, located approximately 1 kilometer from the study area.

This data release presents five data products derived from this survey which are available for download: 1) an orthomosaic image with a resolution of 2.5 centimeters per pixel, 2) a digital surface model (DSM) and digital elevation model (DEM) with resolutions of 10 centimeters per pixel, 3) a topographic point cloud in LAZ format 4) the geographic positions of the ground control points, and 5) the raw aerial imagery in JPG format.