Skip to main content
Enables navigators to compute their position at sea using celestial navigation techniques.
Rise and set
- Calculates the times of rise, meridian passage, and set of the Sun, Moon, the navigational planets Venus, Mars, Jupiter, and Saturn, the 57 bright stars, Polaris and σ Octantis, taking into account all relevant corrections
- Calculates apparent altitude at meridian passage
- Calculates civil, nautical and astronomical twilight times
- Times given to the nearest minute and for any time zone
- Up to 31 days of times can be shown at once
- Takes into account the observer's height above the horizon
Find it
- Tabulates and plots the altitudes and azimuths of navigational bodies for a given date, time and location
- Includes corrections for standard refraction and parallax
- Highlights the best seven or best three stars for observations
- Three different plotting options are available
- Astronomical bodies are easily sorted into alphabetic, magnitude, altitude or azimuth order
Route planner
- Calculates the course and distance travelled, or the position, using rhumb line or great circle navigation
- Calculates how long it will take to get from the start position to your destination, or the speed required to reach the destination at a specified time
- Tabulates position of waypoints at equal intervals, together with their rhumb line distance, course, and the date and UT time
- Accounts for different time zones
- Plots routes on an interactive plot that includes coastal outlines
Sight reduction
- Determines a position (fix) from observations made with a sextant
- Allows the vessel to journey a variable course, which may be a rhumb line on the WGS84 spheroid
- Process of least squares finds the latitude and longitude that minimizes the intercepts of all the observations
- Input data easily checked using the 'Log' from which observations can be selected or deselected for use
- Includes a plot of position lines, fix, vessel course and confidence ellipse, along with coastal outlines
- Provides all the details of the calculations involved so they can be checked against those done by hand
- 'Find Next Phenomena' tool calculates the next sunrise, sunset or twilight based on position and course
- Data and results can be saved to and loaded from a file
Almanac
- Produces data similar to The Nautical Almanac (NP314), but without the need for interpolation
- Tabulates the Greenwich hour angle (GHA) and declination (DEC) for all navigational bodies and first point of Aries (the Vernal Equinox) to a precision of 0.1 arcminutes
- Tabulates the semi-diameter for the Sun, the horizontal parallax (HP) for Venus, Mars and the Moon, and the magnitudes of the stars and planets
Reminder: HMNAO DP330 NavPac and Compact Data v4.2 expires on 31 December 2025. After this date, the software will stop working and customers will not be able to use any of its functionalities.
To avoid any data outage, we strongly advise you to upgrade to the new DP330 NavPac and Compact Data v4.3, which is available to purchase via ADMIRALTY Distributors.
From 1 January 2026, only the new DP330 NavPac and Compact Data v4.3 will be supported at the UK Hydrographic Office.
Title
The HMNAO NavPac User Guide and FAQs
Includes information on getting started, installation, unlocking with Product Key and FAQs.
Title
End-user Licence Agreement (EULA)
Please find the End-user Licence Agreement for the HMNAO NavPac below.
Title
Who to contact?
In the first instance, please contact the distributor that you purchased NavPac from. If they are unable to help, contact the UKHO Customer Service team by email at customerservices@ukho.gov.uk or by phone: +44(0)1823 484444.