Recording the range of height of ground floor level above grade is used where the exact height is uncertain but it is possible for the surveyor to determine a range, or where the height varies more than 1m and the maximum and minimum height can be recorded.

Units: metres

where a= upper bound and b=lower bound  

Example: HFBET: 1.5,0.5  (height ranges between 1.5 m and 0.5 m)