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Sensors 2018, 18(1), 256; https://doi.org/10.3390/s18010256

The HydroColor App: Above Water Measurements of Remote Sensing Reflectance and Turbidity Using a Smartphone Camera

1
Sequoia Scientific, Inc., 2700 Richards Road, Suite 107, Bellevue, WA 98005, USA
2
School of Marine Sciences, University of Maine, 458 Aubert Hall, Orono, ME 04469, USA
*
Author to whom correspondence should be addressed.
Received: 14 December 2017 / Revised: 11 January 2018 / Accepted: 11 January 2018 / Published: 16 January 2018
(This article belongs to the Section Remote Sensors)
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Abstract

HydroColor is a mobile application that utilizes a smartphone’s camera and auxiliary sensors to measure the remote sensing reflectance of natural water bodies. HydroColor uses the smartphone’s digital camera as a three-band radiometer. Users are directed by the application to collect a series of three images. These images are used to calculate the remote sensing reflectance in the red, green, and blue broad wavelength bands. As with satellite measurements, the reflectance can be inverted to estimate the concentration of absorbing and scattering substances in the water, which are predominately composed of suspended sediment, chlorophyll, and dissolved organic matter. This publication describes the measurement method and investigates the precision of HydroColor’s reflectance and turbidity estimates compared to commercial instruments. It is shown that HydroColor can measure the remote sensing reflectance to within 26% of a precision radiometer and turbidity within 24% of a portable turbidimeter. HydroColor distinguishes itself from other water quality camera methods in that its operation is based on radiometric measurements instead of image color. HydroColor is one of the few mobile applications to use a smartphone as a completely objective sensor, as opposed to subjective user observations or color matching using the human eye. This makes HydroColor a powerful tool for crowdsourcing of aquatic optical data. View Full-Text
Keywords: reflectance; turbidity; mobile; smartphone; camera; crowdsourcing; water-quality reflectance; turbidity; mobile; smartphone; camera; crowdsourcing; water-quality
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Leeuw, T.; Boss, E. The HydroColor App: Above Water Measurements of Remote Sensing Reflectance and Turbidity Using a Smartphone Camera. Sensors 2018, 18, 256.

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