Abstract: Linear domain numbers are converted into standard characteristic-mantissa format by left shifting the leading zeros out of the mantissa portion and into the characteristic portion. The resulting normalized mantissa M is separated into a MSB portion m and a LSB portion n: whereM= m + n,andm >> nto accomodate the approximate relationshipLog (M) .perspectiveto. log term + correction term .perspectiveto. Log (m) + 2n/2m' + nwhere m' = the MSB portion of m.Look up tables are provided for supplying the two terms for each mantissa received. The digital radar landmass systems then performs computations using the approximate logs. The answers are returned to the linear domain by an antilog circuit.