Electrical – Measuring Wind Speed Using Ultrasound Transmitter and Receiver

I am currently trying to create an system to measure wind speed, and I know ultrasound is a good way to do it. I want to make my system be lower cost, however, still maintaining 0.5 m/s precision or better.

There are a few ways I thought to do this.

1. Measure time of flight into the wind and time of flight with the wind, and calculate the difference to get wind speed.
2. Measure the shift in phase from the emitted signal to the received signal
3. Use an ultrasound transducer array to determine how much the transimtted sound wave has shifted due to the wind (system oreinted perpendicular to the wind)
4. Measuring intensity of sound with and against the wind.

For method 1, I think I could disassemble and HC-SR04, placing the transducer opposite the emitter. Then I could measure time of flight without reflections. However, the precision is not quite good enough. I want something ~0.5m/s, and it seems like this method will give me ~5m/s. I am wondering if there is a way to improve the precision of this device. Or perhaps there is another device, or other pieces I could use to build my own more accurate version.

For method 2, I'm not sure what electronics I would need to use measure the phase difference. Is there a simply way to measure the phase difference between the output signal and the received signal?

For method 3, I could not find any sensors that are low cost.

For method 4, I believe it should be a 1/r^2 decay, but this may not be a precise enough method.

Please let me know if you have any insight on which methods would work best and how to implement these. Perhaps I would need a combination. I thought about using time of flight to get a coarse measurement and phase shift to refine the measurement

Thanks for the help!

Alex