Thanks for the response.

Can you pls tell the time it will take for arduino to simultaneously perform the following process for each of the LDR sensor installed (total 56)

Calculate the time for which the LDR is low (light not striking)

Using that time value, calculate the distance using the simple speed/time formula

Secondly, do you think that a better sensor then LDR is available in the market to minimize the response time as much as possible? pls mention here.

Thanks