Idea - a more precise range finder (hacking the hc-sr04)

I have recently made an electronic ruler with a hc-sr04 ultrasonic module. The module has a transmitter and a receiver. It has two digital pins, TRIGGER and ECHO. You set TRIGGER high for over 10us, then the module sends 8 pulses of 40khz sound waves, then it puts ECHO high and keeps it high until an echo returns. If you measure the time ECHO is high, you can measure the distance.
I didn't like the performance at all, especially at longer distances, it is not very directional or precise.
My...

Idea - a more precise range finder (hacking the hc-sr04)