Illumination Geometry and Flying Height Influence Surface Reflectance and NDVI Derived from Multispectral UAS Imagery
| Autor: | Carole Helfter, Gillian Simpson, Daniel Stow, Caroline Nichol, Jakob J. Assmann, T. J. Wade |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
anisotropic reflectance
illumination geometry 010504 meteorology & atmospheric sciences Electronics Engineering and Technology NDVI lcsh:Motor vehicles. Aeronautics. Astronautics media_common.quotation_subject UAV Multispectral image 0211 other engineering and technologies Aerospace Engineering Geometry 02 engineering and technology Noon multispectral imagery 01 natural sciences Normalized Difference Vegetation Index remote sensing Artificial Intelligence Contrast (vision) data quality Radiometric calibration 021101 geological & geomatics engineering 0105 earth and related environmental sciences media_common radiometric calibration Parrot Sequoia Vegetation Reflectivity Computer Science Applications Flying height Control and Systems Engineering Environmental science lcsh:TL1-4050 Information Systems |
| Zdroj: | Drones Volume 3 Issue 3 Stow, D, Nichol, C, Wade, T, Assmann, J, Simpson, G & Helfter, C 2019, ' Illumination Geometry and Flying Height Influence Surface Reflectance and NDVI Derived from Multispectral UAS Imagery ', Drones, pp. 1 . https://doi.org/10.3390/drones3030055 Drones, Vol 3, Iss 3, p 55 (2019) |
| ISSN: | 2504-446X |
| DOI: | 10.3390/drones3030055 |
| Popis: | Small unmanned aerial systems (UAS) have allowed the mapping of vegetation at very high spatial resolution, but a lack of standardisation has led to uncertainties regarding data quality. For reflectance measurements and vegetation indices (Vis) to be comparable between sites and over time, careful flight planning and robust radiometric calibration procedures are required. Two sources of uncertainty that have received little attention until recently are illumination geometry and the effect of flying height. This study developed methods to quantify and visualise these effects in imagery from the Parrot Sequoia, a UAV-mounted multispectral sensor. Change in illumination geometry over one day (14 May 2018) had visible effects on both individual images and orthomosaics. Average near-infrared (NIR) reflectance and NDVI in regions of interest were slightly lower around solar noon, and the contrast between shadowed and well-illuminated areas increased over the day in all multispectral bands. Per-pixel differences in NDVI maps were spatially variable, and much larger than average differences in some areas. Results relating to flying height were inconclusive, though small increases in NIR reflectance with height were observed over a black sailcloth tarp. These results underline the need to consider illumination geometry when carrying out UAS vegetation surveys. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|