HMNAO banner

[Skip to Content]

HM Nautical Almanac Office: NavPac 4.1

NavPac 4.1 — Introduction

DP330 2021-2025 cover This page provides a focus for information, issues, updates and bug fixes relating to NavPac 4.1, HMNAO's celestial navigation software package for the PC operating under the Microsoft Windows™ operating system. NavPac version 4.1.1 is supplied on CD in addition to the Admiralty publication DP330 NavPac and Compact Data 2021-2025.

NavPac enables navigators to compute their position at sea using celestial navigation, and also contains features such as calculating great circle and rhumb line tracks. There are also functions for calculating rise and set times and determining the altitude and azimuths of navigational objects. Click here for a tour of the features of NavPac. A full manual is included on the CD which also includes part of the Royal Navy's Admiralty Manual of Navigation (Volume 2).

Additional astronomical data files are also found on the CD, which can be read into any computer. Astronomers, navigators, surveyors and general users will find these data files ideal for making their own astronomical calculations where positions of the Sun, Moon, planets and bright stars are required.

NavPac is used world-wide by the Royal Navy (RN), other navies and by navigators who require an independent means of navigation. The RN Initial Warfare Officer (IWO) qualification is the equivalent of the Standards of Training, Certification and Watchkeeping (STCW) navigational watch certificate, and by obtaining the Ocean Navigation Certificate, which is an element of the IWO qualification, the student uses NavPac as installed on RN vessels. The tables and coefficients and the algorithm for determining position at sea from observations made with a marine sextant have been used by navigators since 1981. NavPac version 4.1.1 is supplied on CD with NavPac and Compact Data 2021-2025.

NavPac 4.1 Minimum System Requirements

† – Minimum supported operating system

Unlocking NavPac Software

The installation process for NavPac 4.1 uses a contact e-mail address, a product key and a machine signature generated during the installation process. The software requires an unlock code which can be generated on this page. This information is held on our web site which enables HMNAO to advise users of updates and bug fixes to the software as and when they become available.

Problems with NavPac 4.1

If you have any problems with the NavPac 4.1 software or wish to report an error, please e-mail or use the Feedback page.

Patches for NavPac 4.1

A patch file is available as of 2021 March 29th to update the NavPac 4.1.1 software to version 4.1.2. Instructions are available to assist with the installation of the patch. We have also prepared an iso file for download which contains the patch file and the instructions pdf file. You can burn this iso file to a CD should you wish to use this method instead of downloading the patch file directly as some browsers will warn you of the risks of downloading a patch file directly. All three of these files have been screened for viruses.

© Crown Copyright 2008-2021 / Privacy Policy
Last modified: Monday, 18 October 2021 at 10:36:44 BST