Aboard Map: a free offline deck map for P&O Iona and Arvia

Your phone's maps go dead the moment you turn your data off

Sixteen passenger decks on Iona and Arvia, numbered 3 to 19 with no deck 13. The fold-out paper plan in your cabin shows all of it. The one thing it can't show is you.

So you end up at a lift lobby, working out whether the place you want is above you or behind you, and whether those stairs go that far.

Your phone is no help either. You'll be told to turn your mobile data off before the ship sails, and it's good advice.

Once the ship is past territorial waters, with the coast still in view, your phone picks up the ship's own mast, and no bundle covers that. It's maritime data, billed on its own at £6 a megabyte. One photo sent home can cost thirty pounds.

So you switch it off. Then you open the map app you use everywhere else on earth and there's nothing in it.

Aboard Map loads once, at home, and after that it lives on your phone.

I built this because I couldn't find the Crow's Nest

I'm a passenger. I went looking for the Crow's Nest, the observation lounge with the best view on the ship, and I couldn't find it. It's at the extreme forward end of deck 17, and deck 17 runs almost the whole length of the ship, so knowing the deck number doesn't get you there.

On the sea day sailing home to Southampton I built the first version of this map, and posted it in a P&O Facebook group. What happened next is at the top of this page.

It's free, there are no ads, and I'm not selling anything.

Why there's no dot that follows you

Satellite positioning needs a view of the sky. Stand in a corridor on deck 9 and there are nine more decks of steel above your head, so it doesn't work: the dot you're used to on land either sits still or drifts off into the sea.

Wi-fi and Bluetooth would be the next thing to try. A web page in your browser can't watch for either of them in the background, and on an iPhone it can't see Bluetooth at all.

So Aboard Map uses the one landmark the ship already gives you. Every cabin door has its number beside it, thousands of them, along every corridor of every cabin deck. Tap "Where am I?", point the camera at the number beside any door, and the map shows where you're standing. You can also just type the number in.

Your position updates when you scan, not by itself, so the dot goes quiet after a couple of minutes.

What it does

Shows you where you are

Type your own cabin number in once and it stays saved, and every route starts from your own door. Finding the rest of the ship from there is the job.

Walks you to anywhere on board

Tap "Find", type a place or a cabin number, and it draws the walk: which of the three sets of stairs and lifts to head for, and how far up or down. FWD, MID and AFT are the ship's own words for those three, front, middle and back. Walking times come from the distance at a steady pace, so these times are a guide, not a promise.

The bars, restaurants, pools, shops and toilets are all on the map, and every one of them has a line saying what it is. Where a place costs extra, it says so. Search for toilets and the nearest one comes first. Zoom right in on a cabin deck and every cabin number appears.

Tells you which port, and which day

It knows which cruise you're on, too. Give it the dates you sail and it lists your stops: the day, the place, and the hours you have ashore.

Your stops on a phone: P&O Iona, Norwegian Fjords, seven nights, sailing 12 September 2026. Eight days are listed, from leaving Southampton at 17:00 to arriving back at 07:00, with Stavanger, Alesund, Olden and Haugesund in between and the hours ashore beside each one.

Says what's worth doing when you get off

Each stop is split in two: what costs nothing, and what costs money. The free half is what you can walk to from the gangway, and how long it takes. The paid half names the thing and says how you reach it, since the sight everybody comes for is usually a long way inland.

No prices and no opening times. Both go stale in a file that sits on your phone for a month, and a wrong one costs you a morning.

Every port I have written up has a page of its own too, outside the app: what to do at each stop.

Before that, there is a checklist of the things worth doing at home: before you sail.

The Olden page on a phone, below the street map: under a heading reading Costs nothing, the flat fifteen-minute walk along the fjord to the village, the old church of 1759 and the house an American painter built in 1912. Under Costs money, Loen Skylift with the marked paths from the top of it, the Briksdal glacier, the Kjenndal glacier boat and a self-guided ATV ride in the valleys behind the village, each with a sentence saying what it is and how far out it lies. — This one is Olden.

It keeps working after the signal goes

Open it once on wi-fi at home and it copies itself onto your phone's own storage: every deck, every cabin, every venue, every route. After that it asks the internet for nothing. Mid-Atlantic or in a lift, it's the same app.

Saves the street maps for your own stops

The ports take one step more. Tell it the dates you sail and it works out which stops are yours, then a button saves the maps for those places. It shows you the size before you agree.

There are maps for 55 places the two ships call at, ports and Norwegian fjords, and it only ever saves the ones on your own cruise. Save them at home and you have the streets of Rotterdam on your phone with no signal and no bill.

The Stavanger page on a phone: a paragraph about the herring town that struck North Sea oil in 1969, a note about the twenty-three life-size iron men standing around the town, and the street map of the harbour below it. — Every stop has a page of its own, and a street map you can save before you sail. This one is Stavanger.

The two ships, and which one is better checked

Both ships are in the one app and you pick yours at the top of the screen. Counted off P&O's own deck plans, Iona has 2,611 cabin positions in it and Arvia 2,656, on eleven cabin decks each.

Iona is the better checked of the two. Its positions come from P&O's own deck-plan PDF and a second independent redraw, and its cabin numbers are lined up against photographs of the ship's own lift-lobby boards.

Arvia has no such anchor. Same plan, same second redraw, but its frame is measured from the drawing and squared up against Iona, and its fares were researched from cruise guides rather than P&O's own pages. Nobody has yet walked either ship checking the map against the real thing.

Two ships so far. More as I get to them, and the mailing list is where I'd say so.

What this is not

It isn't P&O's own app and it doesn't pretend to be. It can't book you a table and it can't see your booking. Once you're aboard there's a My Holiday button in it, which opens P&O's own site on the ship's wi-fi.

Nothing in Aboard Map has been measured aboard with a tape. If a room has been renamed since the plan was drawn, the plan is what the app believes, so there's an "email a correction" link inside it and the email comes to me. I fix it for everyone.

There's no account and nothing to sign in to. It counts visits and app launches anonymously, and your position never leaves your phone.

Aboard Map is an independent guide made by a passenger. It is not affiliated with or endorsed by P&O Cruises. Positions come from the published deck plan. And the map is a sketch: places are where they really are, but walls and corridors aren't drawn.

Common questions

Will it work when my phone data is switched off?

Yes, and that's the point of it. Open it once while you still have wi-fi and it saves itself to your phone, so after that it needs no connection at all. Ships bill mobile data as maritime data, at £6 a megabyte, which is why you're told to switch your data off, and why every other map on your phone stops working when you do.

Do I have to download an app from the App Store?

No. It's a web page. Open aboardmap.com in your browser, add it to your home screen, and it opens full screen with its own icon. No app store, no account, no sign-in, and nothing to update by hand: it updates itself whenever it has a connection.

Which ships does it cover?

P&O Iona and Arvia, both built from P&O's own deck plans. Decks 3 to 19 on each, with no deck 13, and cabins on eleven of them: 4, 5, 8, 9, 10, 11, 12, 14, 15, 16 and 17.

How does it know where I am on the ship?

You give it a cabin number, either typed in or read off the number beside any cabin door with the camera, and it puts you on the deck map.

There's no dot that follows you around, because a steel hull blocks satellite positioning and a web page can't watch for wi-fi or Bluetooth in the background. Your position updates when you scan, not by itself, so the dot goes quiet after a couple of minutes.

Is it really free? What's the catch?

It's free, and there's nothing to buy. It counts visits and app launches anonymously, your position never leaves your phone, and if you sign up, all that's kept is your email and your sailing, and nothing else about you. GDPR wants a company name against that, and mine is Immersi. I made it as a passenger because I got lost. If it saves your holiday you can buy me a pint, and that's the whole of it.

Is my cabin on the port side or the starboard side?

On both ships, even numbers are on the port side, the left as you face the front, and odd numbers are on the starboard side, the right.

I checked it against every cabin position on P&O's own deck plans.

Two things stop it being the whole answer, cabins near the middle of the ship and the rows at each end of a cabin deck, and the Iona and Arvia pages set both out.