In olden times different types of measurment s like cubit,stride handspan,footspan etc were used.Different people different types of these measuement.,since they are different in size.that is small person will have small measurments while bigger ones will have long or higher measurments.Then we wont get correct or accurate measurments.So we are using standard system of measurments for length.mass and time .they are meter,kilogram.and seconds