Non-invasive method and device to measure the flow rate of a river, open channel or fluid flowing in an underground pipe or channel

A non-invasive method for measuring velocity measurement and distribution of a fluid flowing through a pipe or channel or in a river or open channel, the method using a non-invasive microwave fluid velocity measuring device suspended from a drone and comprising one or more vibration sensors, said method comprising the steps of:

• a. generating microwave signals by using a patch antenna or horn antenna;
• b. receiving microwave signals from a flowing fluid surface (16);
• c. generating a plurality of discrete data expressed in amplitude as a function of time from the generated microwave signals and the reflected microwave signals with Doppler frequency shifts;
• d. transforming a spectrum of data expressed in the temporal domain into a frequency domain via a Fourier transform to fit a first Gaussian curve;
• e. determining global measured velocity and global velocity distribution via the first Gaussian curve;
• f. measuring mechanical vibrations of the drone during the steps (a) and (b) of generating and receiving signals, to determine a sequence of vibration data being measured by the vibration sensor;
• g. generating, from the vibration data, a plurality of discrete data expressed in amplitude as a function of time;
• h. transforming a spectrum of vibration data expressed in the temporal domain into a frequency domain via a Fourier transform to fit a second Gaussian curve;
• i. determining measured vibration induced velocity and vibration induced velocity distribution via the second Gaussian curve.
• j. applying a correction to the global measured velocity and the global velocity distribution obtained in step (e) by subtracting the measured vibration induced velocity and vibration induced velocity distribution obtained in step (j) to eliminate the vibrations of the drone in calculation of real velocity measurement and real velocity distribution of the fluid.