Invar tapes:

For accurate measurements, steel tapes are used. These consist of light strip of steel with width ranging from 6 to 10 mm, in lengths of 2 to 50 m. Instead, steel bands consisting of ribbon of steel along with brass swivel handle at every end are used. The width is commonly 16 mm and length of 20 or 30 m.

Steel tapes and bands could be more accurately graduated. The graduations are etched as meters, decimeters and centimeters on one side and 0.2 m links on other side. Band is generally divided through brass studs at every 20 cm and numbered at every one metre. The tapes and bands are extremely delicate and therefore not suitable for rough usage. These also need frequent cleaning and drying to prevent rusting. It is also hard to read as compared to chain.

Invar tapes of alloy of Nickel (36%) and steel could be used for higher accuracy as their coefficient of thermal expansion is very low. Thus, it is expensive and more delicate in use. In present times, fibreglass tapes are extensively used in the field survey since of its low thermal expansion, strength, cheapness, ruggedness and durability. These are available in ranges varying from 5 m to 30 m in length.