Keywords

runoff, measurement, smartphone, high-tech, low-cost

Location

Session A4: Smart and Mobile Devices Used for Environmental Applications

Start Date

18-6-2014 9:00 AM

End Date

18-6-2014 10:20 AM

Description

For effective water management, particularly in irrigated agriculture, it is essential to have reliable open-channel flow data. With present methods, such data is not readily obtained as they require measurement stations, what often results in sparse data. We present a mobile device app to measure runoff in open channels. With this tool flow data can be collected reliably and cheaply.

The technology, on which the app is based, is derived from an already implemented and tested similar webcam application. The smartphone app calculates the runoff by analyzing a few seconds of a movie sequence that is recorded by the same device. The runoff is calculated from measured water level, surface velocity and from measured or a priori knowledge on the channel geometry. The water level is determined by the separation line of image segments with and without optical flow. Via calibration of the camera position this separation line is mapped to a water level. Then, the surface velocity is calculated using a modified method of the standard Particle Image Velocimetry method. Among the key characteristics of the method is the fact that no tracer particles are needed.

The methodology has been tested for the webcam application in a pilot project in Switzerland. The results show that it is capable to produce continuous and reliable data for water level, surface velocity and runoff. The accuracy is within 5% of data obtained from a commercial radar sensor. The existing preliminary results for the smartphone application indicate similar accuracy. The tool has the potential to become the state of the art method for mobile runoff measurements, as it is truly high-tech and low-cost.

 
Jun 18th, 9:00 AM Jun 18th, 10:20 AM

Mobile device app for small open-channel flow measurement

Session A4: Smart and Mobile Devices Used for Environmental Applications

For effective water management, particularly in irrigated agriculture, it is essential to have reliable open-channel flow data. With present methods, such data is not readily obtained as they require measurement stations, what often results in sparse data. We present a mobile device app to measure runoff in open channels. With this tool flow data can be collected reliably and cheaply.

The technology, on which the app is based, is derived from an already implemented and tested similar webcam application. The smartphone app calculates the runoff by analyzing a few seconds of a movie sequence that is recorded by the same device. The runoff is calculated from measured water level, surface velocity and from measured or a priori knowledge on the channel geometry. The water level is determined by the separation line of image segments with and without optical flow. Via calibration of the camera position this separation line is mapped to a water level. Then, the surface velocity is calculated using a modified method of the standard Particle Image Velocimetry method. Among the key characteristics of the method is the fact that no tracer particles are needed.

The methodology has been tested for the webcam application in a pilot project in Switzerland. The results show that it is capable to produce continuous and reliable data for water level, surface velocity and runoff. The accuracy is within 5% of data obtained from a commercial radar sensor. The existing preliminary results for the smartphone application indicate similar accuracy. The tool has the potential to become the state of the art method for mobile runoff measurements, as it is truly high-tech and low-cost.