Orthomosaic imagery from the UAS survey of the coral reef off Waiakane, Molokai, Hawaii, 24 June 2018
Dates
Publication Date
2022-03-21
Time Period
2018-06-24
Citation
Logan, J.B., and Storlazzi, C.D., 2022, Aerial imagery and structure-from-motion-derived shallow water bathymetry from a UAS survey of the coral reef off Waiakane, Molokai, Hawaii, June 2018: U.S. Geological Survey data release, https://doi.org/10.5066/P9XZT1FK.
Summary
This portion of the data release presents a high-resolution orthomosaic image of the coral reef off Waiakane, Molokai, Hawaii. The orthomosaic has a resolution of 2.5 centimeters (cm) per pixel and was derived from structure-from-motion (SfM) processing of aerial imagery collected with an unoccupied aerial system (UAS) on 24 June 2018. The raw imagery used to create the orthomosaic was acquired using a UAS fitted with a Ricoh GR II digital camera featuring a global shutter. The UAS was flown on pre-programmed autonomous flight lines spaced to provide approximately 75 percent overlap between images from adjacent lines. The UAS was flown at an approximate altitude of 100 meters above ground level (AGL), resulting in a nominal ground-sample-distance [...]
Summary
This portion of the data release presents a high-resolution orthomosaic image of the coral reef off Waiakane, Molokai, Hawaii. The orthomosaic has a resolution of 2.5 centimeters (cm) per pixel and was derived from structure-from-motion (SfM) processing of aerial imagery collected with an unoccupied aerial system (UAS) on 24 June 2018. The raw imagery used to create the orthomosaic was acquired using a UAS fitted with a Ricoh GR II digital camera featuring a global shutter. The UAS was flown on pre-programmed autonomous flight lines spaced to provide approximately 75 percent overlap between images from adjacent lines. The UAS was flown at an approximate altitude of 100 meters above ground level (AGL), resulting in a nominal ground-sample-distance (GSD) of 2.6 centimeters per pixel. The camera was triggered at 1 Hz using a built-in intervalometer. The raw imagery was geotagged using positions from the UAS onboard single-frequency autonomous GPS. Although imagery was collected using both a circular polarizing filter and with no polarizing filter, only the non-polarized imagery was used for the creation of the orthomosaic. SfM photogrammetry was used to derive a preliminary digital surface model (DSM) from this imagery which was used as a surface for orthorectification and mosaicking. The orthomosaic image is provided in a three-band RGB format, with 8-bit unsigned integer values compressed using high-quality JPEG compression. The image has been formatted as a cloud-optimized GeoTIFF with internal overviews and masks to facilitate cloud-based queries and display.
These data were collected to characterize the morphology and rugosity of the shallow fringing coral reef off Waiakane, Molokai, Hawaii, as part of a larger USGS study of nearshore circulation and hydrodynamic properties of coral reefs. The orthomosaic images can be used with geographic information systems (GIS) software for research purposes.
Preview Image
Orthomosaic image from UAS survey of the coral reef off Waiakane, Molokai, HI.