Nav Clock


Q: What is the most recent version of Nav Clock?

A: Version 4.2.4 is the most recent version of Nav Clock on the App Store.  It supports iOS 11.0 and newer.  Tap on the “info” button and select Technical Support. The version number is displayed at the bottom of the table of options.

Q: Abbreviations

A: Δ - Delta Symbol - Daylight gain/loss each day

    AGL - Above Ground LevelAMSL - Above Mean Sea Level

    Crs - Course

    H - The horizontal accuracy of the geographic coordinates as reported by the iOS Location


    in. Hg - Inches of Mercury

    km - Kilometer

    kph - Kilometers per hour

    mb - Millibars

    mph - Miles per hour

    m/s - Meters per second

    Twp - Township

    V - The vertical accuracy of the Elevation Above Mean Sea level as reported by the iOS

          Location Services.

Q: Why does the Nav Clock screen go dark so fast?

A: Your Settings>>General>>Auto-Lock is set to 'Auto-Lock' in a short period of time.  Slide the Nav Clock preference for Disable Auto-Lock to ON to prevent your device from sleeping while Nav Clock is running.  When you quit Nav Clock, the device will again use the system setting you have established for Auto-Lock.

Q: Can I view the status bar to check the status of the battery?

A: Yes. Simply touch anywhere on the Nav Clock screen and the status bar will appear for a few seconds.

Q: What is the tiny yellow Warning Sign icon to the right of the coordinates?

A: The indicator is a reminder that Continuous Location Updating is ON because it uses so much battery power.  It appears if the device is not plugged in and charging.

Q: What is the tiny green Automobile icon to the right of the coordinates?

A: The indicator is a reminder that Continuous Location Updating is ON while driving and the device is plugged in and charging if the option to do so is also ON.  It is ON by default.

Q: Can I copy the geographic coordinates to use in other apps?

A: Yes. Simply press and hold on the geographic coordinates to copy them so that they may be pasted into other apps.

Q: What are Military Time Zones?

A: The United States Military, Chinese Military, and many others across the globe use military time zones to help with planning.  They are used to ensure standardization and effective communication across many different time zones.

Q: What are what3words coordinates?

A: The what3words addressing system is a geographic co-ordinate system that provides a precise and incredibly simple way to talk about location.  They have divided the world into a grid of 3m x 3m squares and assigned each one a unique 3 word address.  For example:  ///

Q: What are Maidenhead coordinates?

A: The Maidenhead Locator System is a geographic co-ordinate system used by amateur radio operators.  Dr. John Morris, originally devised the system, and a group of VHF managers, meeting in Maidenhead, England in 1980, adopted it.

Q: What are VFR, MVFR, IFR, and LIFR?

A: VFR, MVFR, IFR, and LIFR are aviation conditions of flight:

   VFR - Visual Flight Rules

      Ceiling greater than 3000 feet and visibility greater than 5 miles (includes sky clear).

   MVFR - Marginal Visual Flight Rules

      Ceilings 1,000 to 3,000 feet and/or visibility is 3-5 miles inclusive.

   IFR - Instrument Flight Rules

       Ceilings 500 to less than 1,000 feet and/or visibility 1 to less than 3 miles.

   LIFR- Low Instrument Flight Rules

       Ceilings are less than 500 feet and/or visibility is less than 1 mile.


Q: Why don't Course and Speed appear?

A: The Course and Speed will appear if:

   1. Your device supports motion.

   2. You have authorized Motion and Fitness.

      Settings>>Privacy>>Motion and Fitness

   3. You are walking, running, cycling, or driving.


Q: What is a Maintenance Flag?

A: A METAR ending with a $ indicates that the weather reporting equipment at this weather station has been flagged for a maintenance check to be performed.


Q: What is Pressure Altitude?

A: Atmospheric pressure expressed in terms of altitude which corresponds to that pressure in the standard atmosphere.

Q: What is Density Altitude?

A: Density Altitude is the pressure altitude adjusted for non-standard temperature.

Q: What is a METAR?

A: A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting.

Q: What is Civil Twilight?

A:Civil Twilight: the time at which the sun is 6 degrees below the horizon. At this time, there is enough light for objects to be clearly distinguishable and that outdoor activities can commence (dawn) or end (dusk) without artificial illumination. Civil twilight is the definition of twilight most widely used by the general public.

Q: What is Nautical Twilight?

A: Nautical Twilight: the time when the center of the sun is 12 degrees below the horizon, and only general or vague outlines of objects are visible. During the evening this is when it becomes too difficult to perceive the horizon, and in the morning this is the point when the horizon becomes distinguishable. This term goes back to the days when sailing ships navigated by using the stars.

Q: What is Astronomical Twilight?

A: Astronomical Twilight: the time at which the sun is 18 degrees below the horizon. It is that point in time at which the sun starts lightening the sky. Prior to this time during the morning, the sky is completely dark. During the evening, this is the point where the sky completely turns dark.

Q: Why are some settings disabled?

A: 'Show Elevation AMSL' requires a GPS and is therefore only enabled devices with a GPS.  'Show Elevation AMSL' and 'Show Accuracy' are disabled when Use Location Services is turned OFF because the iOS Location Services will not be providing that information.

Q: Why don’t the geographic coordinates update and instead just show “…”?

A: iPad® and iPod® touch can only determine their location using Wi-Fi by accessing a major public or commercial Wi-Fi hot spot, not just your home or office Wi-Fi.  For example, if the Maps App cannot determine your location, Nav Clock will not be able to either.

Q: Why isn't my airport listed for a Preferred Weather Station?

A: When selecting a Preferred Weather Station, only airports within 60 miles are listed.  That airport will then be used for obtaining weather reports as long as it remains with 60 miles.  Otherwise, the nearest airport to you location is used.

Q: Why did the weather “Fail to Update”?

A: 1. See 'Why don’t the geographic coordinates update and instead just show …?'  Nav Clock must know your location before it can get the current weather report.

      2. Using Wi-Fi only: Many Wi-Fi hot-spots require that you log onto the site page before you can actually use the Internet.  It may appear that Nav Clock can use the Internet but it really can’t.  A good test is to use Safari to be sure you can access a few web pages.

Q: Why is the location accuracy only in thousands of feet?

A: When your device first determines your location it uses cell towers or Wi-Fi hot spots which are not very accurate - however they are accurate enough for Nav Clock to get the weather in your vicinity.  For devices with GPS, as they acquire or 'see' more satellites, the accuracy will improve greatly - this may take a minute or so.  The accuracy of the GPS changes based upon your movements as buildings, trees, and sky conditions all have an influence on how many satellites the device can 'see'.

Q: Why does the elevation show “...”?

A: Elevation AMSL requires a GPS and therefore is only available on devices with GPS.  Your device must 'see' several satellites in order to determine your elevation.  The elevation will display '...' until the iPhone has determined your elevation.  As the iPhone acquires or 'sees' more satellites the accuracy will improve greatly - this may take a minute or so.  The accuracy of the GPS changes based upon your movements as buildings, trees, and sky conditions all have an influence on how many satellites the iPhone can 'see'.  For best results you may need to be outside.

Q: What is the Feels Like temperature?

A: Nav Clock clock calculates the Wind Chill or the Heat Index based upon temperature, wind speed, and the humidity.

Q: What is the source of Nav Clock's weather reports?

A: For the most accurate weather reports, Nav Clock uses aviation METARs from airports from around the world from NOAA’s National Weather Service (NWS).  Nav Clock checks for updated weather reports about every 15 minutes from the airport nearest to your location.  These weather reports my be out of date.


Q: If I re-download Nav Clock will I be charged for it again?

A: You may re-download Nav Clock on the App Store as often as you need at no additional charge.

Q: Do you have a Privacy Policy?

A: You may access our Privacy Policy under Technical support in the Nav Clock Settings or visit our web site.


Q: Are there any new features planned for Nav Clock in future updates?

A: Tap on 'Breaking News' in this section to learn about new features or bug fixes that are planned for the next versions of Nav Clock.

Q: What if there is any new information that I need to know about Nav Clock?

A: Tap on 'Breaking News' in this section to learn the latest Breaking News about Nav Clock.

Q: What if my question wasn’t answered here?

A: Please submit your support questions or other feedback to us by selecting 'Provide Feedback' in this section or via our 'Contact Us' form at We try to answer every e-mail that we receive.

Frequently Asked Questions