The multiplying constant ($K$) is generally kept at $100$.

The additive constant ($C = f + d$) is usually kept at $0$ by providing an anallatic lens in modern tacheometers.

Using an anallatic lens makes the distance directly proportional to the staff intercept ($D = 100s$).

Eliminates the need for physical chaining or taping over rough terrain.

Provides rapid survey measurements for topographic mapping.

Significantly simplifies field office calculations when $K = 100$ and $C = 0$.

Precision is lower compared to precise electronic distance measurement (EDM) or invar tape chaining.

Accuracy decreases at longer sight distances due to reading errors on the staff.

Contouring and topographic surveying in hilly or rugged terrain.

Location surveys for roads, railways, and reservoirs.

The additive constant $C = f + d$ ranges from $30\text{ cm}$ to $45\text{ cm}$ for external focusing telescopes and $8\text{ cm}$ to $20\text{ cm}$ for internal focusing telescopes.

Anallatic lens (invented by Porro) reduces the additive constant $C$ to strictly zero.