HydroColor: Water Quality App at App Store analyse

App power index: 260 (based on ranks around App Stores today)
Utilities Education
Developer: Thomas Leeuw
Price: 0 free
Current version: 2.2, last update: 9 months ago
First release : 14 Feb 2014
App size: 85.11 Mb
4.6 ( 5696 ratings )
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Estimation application downloads and cost

> 5.72k
Monthly downloads
~ $ 2.34k
Estimation App Cost


HydroColor is a water quality application that uses the iPhone camera to determine the reflectance of natural water bodies. Using this information, HydroColor can estimate water turbidity (0-80 NTU), concentration of suspended particulate matter (SPM) (g/m^3) and the backscattering coefficient in the red (1/m). IMPORTANT: HydroColor requires the use of an 18% photographers gray card as a reference. Gray cards are widely available at photography shops and online. Visit the supporting website for more information on gray cards.

HydroColor has an easy to use interface that guides users through the collection of three images: a gray card image, a sky image, and a water image. To ensure the best results, HydroColor taps into the iPhone’s GPS, gyroscope, and compass to aid users in the collection of these images. After images are collected they can be analyzed immediately. In the analysis of the images, HydroColor calculates the reflectance of the water body in the RGB color channels of the camera. It then uses the reflectance values to determine the turbidity of the water in NTU (nephelometric turbidity units).

The data is instantly saved and can be accessed again via HydroColor or downloaded onto a computer from the documents folder (accessible in iTunes). The text file contains additional information about the measurement including: latitude, longitude, date, time, sun zenith, sun azimuth, phone heading, phone pitch, exposure values, RGB reflectance, and turbidity. Additional water quality parameters (e.g. chlorophyll concentration) will be added to HydroColor as research continues. Proceeds from HydroColor will go toward developing additional algorithms for HydroColor and to creating additional Apps like HydroColor.

How it works:

HydroColor uses the iPhone camera as simple light sensor (photometer). Relative light intensity can be measured by normalizing the camera pixel values by the exposure. Therefore, the three color channels of the camera (RGB: Red, Green, Blue) provide a measure of light intensity in three regions of the visible spectrum.

The light intensity measured in the water image is corrected for sky reflection off the surface (using the sky image). The corrected water image provides the intensity and color of light emanating from the water. This is normalized by the ambient illumination using the gray card image. The final product is a nearly illumination independent measure of the water’s reflectance, known as remote sensing reflectance. In oceanography, satellites are used to calculate the same product (remote sensing reflectance) from space.

The reflectance is directly related to the amount and type of suspended particles in the water. An increase in turbidly (i.e. suspended sediments) will cause greater scattering of light and increase the overall reflectance of the water. Particles containing pigments, such as phytoplankton (algae), will absorb light in specific regions of the visible spectrum. Thus, pigment containing particles can be detected by comparing the relative reflectance in the RGB channels.
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# Term Store county Place Priority
1 lake coloring 11 ⭐️⭐️⭐️⭐️
Available in countries
Country Price
Canada free
China free
France free
Germany free
Italy free
Netherlands free
Portugal free
Spain free
Poland 3.49 EUR
UK free
India free
Japan free
Korea, Republic Of free
Poland free
Russia free
Turkey free
USA free
Korea, Republic Of 3.29 USD
Ukraine free
Available for devices
iPhone4, iPad2Wifi, iPad23G, iPhone4S, iPadThirdGen, iPadThirdGen4G, iPhone5, iPadFourthGen, iPadFourthGen4G, iPadMini, iPadMini4G, iPhone5c, iPhone5s, iPadAir, iPadAirCellular, iPadMiniRetina, iPadMiniRetinaCellular, iPhone6, iPhone6Plus, iPadAir2, iPadAir2Cellular, iPadMini3, iPadMini3Cellular, iPodTouchSixthGen, iPhone6s, iPhone6sPlus, iPadMini4, iPadMini4Cellular, iPadPro, iPadProCellular, iPadPro97, iPadPro97Cellular, iPhoneSE, iPhone7, iPhone7Plus, iPad611, iPad612, iPad71, iPad72, iPad73, iPad74, iPhone8, iPhone8Plus, iPhoneX, iPad75, iPad76, iPhoneXS, iPhoneXSMax, iPhoneXR, iPad812, iPad834, iPad856, iPad878, iPadMini5, iPadMini5Cellular, iPadAir3, iPadAir3Cellular, iPodTouchSeventhGen, iPhone11, iPhone11Pro, iPadSeventhGen, iPadSeventhGenCellular, iPhone11ProMax, iPhoneSESecondGen, iPadProSecondGen, iPadProSecondGenCellular, iPadProFourthGen, iPadProFourthGenCellular,