Invar Grade Rods

Invar Grade Rods are used in land surveying when first-order high-precision elevation leveling is to be performed. The Grade Rod, also known as Leveling Rods and Elevation Rods are made of Invar which is a nickel–iron alloy notable for its uniquely low coefficient of thermal expansion. The name "Invar" comes from the word invariable, which refers to its relative lack of expansion or contraction with temperature changes which directly lends itself to making the most reliable rod for measuring elevation changes in land.