by Jonas van Duijvenbode (The Netherlands)
Image acquisition with UAV’s offer great possibilities for remote sensing problems like data gaps and can improve operational flexibility.
The remote sensing community devotes major effort to the quality of image data.
Unregistered irradiance changes during an UAV-based image acquisition flight can have a large negative effect on this quality.These changes are dependent on atmospheric conditions and need to be monitored and corrected for.
Direct incident light sensing with irradiance measuring instruments and empirical line correction with reference reflectance panels offer this possibility.
In this research, both methods have been evaluated for stratus, cumulus and cirrus cloud conditions and a clear sky atmosphere.
Empirical line correction showed promising results for clear sky and complete overcast conditions.
Direct incident light sensing is suitable for irradiance monitoring under most cloud conditions, besides cumulus conditions or other situations with abrupt and large irradiance changes.
Incident light measurements need to be made as often and as close to the UAV as possible, spectral resolution is not an important factor.
In this research irradiance monitoring and correction on UAV-acquired images has been applied in the field.The results showed that, although there are yet unknown factors that can negatively influence the quality of incident light correction, in general it can be stated that with simple methods UAV-acquired images can be much improved.
Keywords: remote sensing, UAV, irradiance monitoring, incident light sensing, empirical line correction