Measurement length accurately.

 We should take the following precaution in order to measure the length of an object correctly.

1. Error due to wrong site angle.

The eye should be placed vertically above the end where the reading is to be taken.

2. Error on the position of scale.

 The ends off the ruler must not be worn out.In case the ruler is still in  use,any other fullmark on the ruler should be used. As shown in the given figure.