Digitally Capturing Sites EaPd-7 & EaPd-8
An Unmanned Aerial Viechal (UAV) was deployed at sites EaPd-7 & EaPd-8 to collect data for photogrammetric and multispectral surveys. These two techniques were used to help locate known stone circles and identify potential new stone circles.
Photogrammetric Survey
The photogrammetric survey used the DJI Phantom 4 UAV with the onboard camera, a ½.3 inch CMOS sensor, to take images and all six flights were planned and executed from the Pix4D Captureon an iPad over two days. The flights were flown in a single grid formation at 70 m above ground level with 85% overlap between images on the same grid line and 70% overlap between images on adjacent grid lines. This collected 1409 images and covered 39.5 hectares. The 1409 images recorded in the Pix4D Capture were upload to Pix4Dmapper Pro v. 4.2.26 and processed to produce an orthomosaic and Digital Surface
Model (DSM).
Multispectral Survey
For the multispectral survey, the DJI Phantom 4 was flown with the Parrot Sequoia + sensor, which has a 16-megapixel RGB camera, four 41.2-megapixel global shutter single-band cameras, and a sunshine sensor equipped with GPS. The sensors were calibrated before take-off with a radiometric calibration
target and the flight planned and executed from the Pix4D app on an iPad. The flight was flown in a single grid formation at 70 m above ground level with 186o images taken and covered 11.8 hectares. Images were processed in Pix4Dmapper Pro v. 4.2.26 with the index calculator to create the red, green,
near-infrared and red-edge reflectance value images which were then used to create the Normalized Difference Vegetation Index (NDVI) image. This raster image was then taken into ArcGIS Pro v10.6.1 where the raster was polygonised according to pixel values, the values associated with the stones in the landscape were then turned into a shapefile to be integrated with the ASA data.
