Sensors, Vol. 20, Pages 6580: Measurement of Water Leaving Reflectance Using a Digital Camera Based on Multiple Reflectance Reference Cards

Sensors, Vol. 20, Pages 6580: Measurement of Water Leaving Reflectance Using a Digital Camera Based on Multiple Reflectance Reference Cards
Sensors doi: 10.3390/s20226580
Authors:
Min Gao
Junsheng Li
Fangfang Zhang
Shenglei Wang
Ya Xie
Ziyao Yin
Bing Zhang

With the development of citizen science, digital cameras and smartphones are increasingly utilized in water quality monitoring. The smartphone application HydroColor quantitatively retrieves water quality parameters from digital images. HydroColor assumes a linear relationship between the digital pixel number (DN) and incident radiance and applies a grey reference card to derive water leaving reflectance. However, image DNs change with incident light brightness non-linearly, according to a power function. We developed an improved method for observing and calculating water leaving reflectance from digital images based on multiple reflectance reference cards. The method was applied to acquire water, sky, and reflectance reference card images using a Cannon 50D digital camera at 31 sampling stations; the results were validated using synchronously measured water leaving reflectance using a field spectrometer. The R2 for the red, green, and blue color bands were 0.94, 0.95, 0.94, and the mean relative errors were 27.6%, 29.8%, 31.8%, respectively. The validation results confirm that this method can derive accurate water leaving reflectance, especially when compared with the results derived by HydroColor, whic...

Source: Sensors - November 18, 2020 Category: Biotechnology Authors: Min Gao Junsheng Li Fangfang Zhang Shenglei Wang Ya Xie Ziyao Yin Bing Zhang Tags: Article Source Type: research