Define precision and accuracy. Identify each of the following errors according to its source…

Define precision and accuracy.  Identify each of the following errors according to its source (natural, instrumental, personal): *(a) Level rod length. (b) EDM–reflector constant. (c) Air pressure in an EDM observation. (d) Reading a graduation on a level rod. (e) Earth curvature in leveling observations. (f) An inclined line of sight in an automatic level.