±2 mm

±3 mm

±5 mm

±8 mm

is lighter than chain

is easier to handle

is practically inextensible and is not liable to kinks when in use

can be easily repaired in the field

centre of one handle to centre of other handle

outside of one handle to outside of other handle

outside of one handle to inside of other handle

inside of one handle to inside of other handle

The true meridians at different places are parallel to each other.

The true meridian at any place is not variable.

The true meridians converge to a point in northern and southern hemispheres.

The maps prepared by national survey departments of any country are based on true meridians.

0° 30'

89° 30'

90° 30'

269° 30'