NavPac software enables navigators and astronomers to compute their position at sea. It provides methods for calculating the positions of the Sun, Moon, navigational planets and stars over several years to a consistent precision, with the aid of a pocket calculator, personal computer or laptop.

This publication is used by the Royal Navy and by many navigators who require an independent means of navigation.​​

DP330 is a new CD-based edition of NavPac and Compact Data covering the period 2021-2025. The NavPac software (v4.1) runs on a PC under Microsoft Windows (8/10) providing the navigator with a simple and efficient method of calculating his position at sea using sextant observations. It also provides rise/set times and positions of the Sun, Moon, planets and navigations stars for planning astronomical sights. It can also calculate great circle and rhumb line tracks.