No matter how good navigation apps have become, using your smartphone as a main method of navigation is just not a good idea. The screen is tiny and you’ll struggle to get a global view of what is ahead and how quickly you may arrive at critical points on your passage.

But when all else fails it can be a great back up to get you home and a useful tool for situational awareness. I have ended up using my phone on several occasions when caught out. Here are a few of my tips for making the most of your pocket-sized computer and staying safe on passage.

Be prepared

However you navigate it’s always a good idea to have a ‘road book’ or passage plan made up before leaving the dock. If you haven’t done this preparation and end up reverting to emergency smartphone navigation then get yourself to a known position – head offshore to deeper water if necessary – and hit pause for a while.

This could be hove-to, or just plodding along with the jib rolled at a low, controllable speed to give yourself enough time to map out a course.

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Visualise your depth

Due to screen size it’s difficult to ‘walk the course’ on a phone, but before heading straight into ‘following the dot’ try to get an overview of your passage and write down the key points where you need to change course or pay attention.

An easy way of getting this overview is to adjust the depth shading on your app. Most apps will allow at least two areas of shading in different colours. Initially set one of these up to reflect the draught of your boat and current conditions.

For example, if sailing with a draught of 2m and conditions are relatively flat, set the first shading to 4m and leave the second one white. This will allow you to zoom out to view the whole passage.

Although you will lose the detail you will still clearly see any areas that could pose a problem, enabling you to route around them.

Identify each of these areas, make a note of where they are and roughly what time on passage you will near them, and then zoom in to see the detail.

Looking at the data in this way will enable you to set up a course quite quickly before doing a final check ‘walking’ along your line at full zoom.

Go old school and use a pen and paper to make those notes, then when the planning has been done leave your shallow water shading set up to suit the passage.

If a second shading option is available then add this to allow quick verification with your depth sounder of where you are on the route, for example, by setting it to 10m.

Using waypoints

Inserting a waypoint into your phone can be as easy as touch and go. Press the screen and a line to follow will appear with a course and distance. But there are a couple of common sense points to observe when marking these positions:

• Ensure you are zoomed in enough to place the waypoint at exactly where it needs to be. It’s tricky to get this level of accuracy on smaller screens.
• Once a route has been established, carefully search down it to ensure there are no surprises or dangers along the way – the depth shading tool can be useful for this.
• Auto-routing functions, which automatically create a route from destination to dock, are a great way to quickly get going, but ensure you have the correct specifications for your boat in the settings.
• Especially if you regularly sail on different vessels, having the correct draught and safety margin is essential.
• Never follow the auto-route blindly, always check the length of the route zoomed in before following it.
• Use markers to highlight areas of concern or ‘guard zones’. Depending on which app you use, markers are often placed on a different layer of information and so will stay visible even when you zoom out and lose other information. It can be useful to use markers instead of waypoints.

Limitations

As good as smartphone navigation apps are, the limitations should be taken seriously so never set out with your phone as a primary means of navigation.

If there is any chance you’ll be using smartphone navigation as a back up make sure you have downloaded all the charts you might need.

Zoom in: The dangers of navigating at too low a zoom level are well documented.

Wet weather: This is a perennial problem for touch screens and, in the wet, phones can be impossible to operate.

Look out of the boat: Always back up your position and your plan with visual real world data. Look out of the boat and match your surroundings to the screen. Use the depth sounder to confirm your location.

GPS: The GPS in an average phone is reasonably accurate but can lose signal, or have a delay in position reporting. Never rely on it to be 100% correct, so if it becomes your only means of navigation set higher margins of safety on your course.

Useful tools

Here are a few tricks for using the in-app tools to help with navigation:

Clearing bearings: Use the measuring tool to mark clearing bearings, which can be visually checked with a hand-bearing compass as you sail. This is great for making landfall.

Record your track to show the effects of tide and wind shifts: Displaying the track can show the distance between COG and heading, as well wind shifts if sailing to wind.

Laylines: To estimate where you should tack, work out what your next heading should be based on current course and estimated tide, then place one end of the measuring tool where you wish to end up and lay the other end across your projected track.

First published in the January 2020 edition of Yachting World.