Precise measurements of physical quantities are need of science

Precise measurements of physical quantities are a need of science, e.g., To ascertain the speed of an aircraft, one must have an accurate method to find its positions at closely separated instants of time. This was the actual motivation behind the discovery of radar in world war II. Think of different examples in modern science where precision measurements of length, time, mass etc., are needed. Also, wherever you can, give a quantitative idea of the precision needed.

Precise measurement of physical quantities such as length, time, mass etc., is a basic requirement of development of astronomy, nuclear physics, medical sciences, crystallography etc.
In the measurement of astronomical distances such as the distance of moon from the earth by laser beam, an accurate measurement of time is required.
A very small mistake in the measurement of that time can produce a large mistake in the accurate distance of moon from the earth, which can be a cause of failure to reach the moon. This time is of the order of ${{10}^{-9}}$s.
In atomic or nuclear reactions, in nuclear weapons and in nuclear power plants, a precise measurement of mass and time is required which is of the order of ${{10}^{-9}}$ kg and ${{10}^{-9}}$s. A small mistake can be a cause of an accident such as take place in Japan recently.
In medical sciences, a precise measurement of length is required to find location, size and mass of tumor in body (it is of the order of${{10}^{-9}}$m).
A small mistake in the measurement of its location, size or mass can be a cause of damaging any body part in laser therapy.