Which is the best sat nav app for iPhone?

When it was announced that the iPhone 3G had a proper GPS chip inside it (the original could only work out its location very roughly by looking at which cell phone masts were nearby), we all got very excited at the prospect of using the iPhone as a turn-by-turn satellite navigation system.

The idea that you could jump in your car, slot the iPhone into a cradle, and have it direct you to your destination, guided by billions of dollars of satellite infrastructure, was beguiling. Especially since even the cheapest standalone sat nav costs more than £100…

The reality, sadly, turned out to be less utopian. The built-in Google-powered Maps app is undoubtedly fantastic, but while it lets you plan journeys by car, foot or public transport, it doesn't provide turn-by-turn directions; that is to say, it doesn't follow you as you drive and tell you when to make your turns.

No matter, you might think, I'll just buy an app from, say, TomTom that does do turn-by-turn. Not so fast; it's only with the release of iPhone OS 3.0 that Apple has actually allowed the development of third-party apps that offer such detailed directions.

Since 3.0 hit, though, we've been treated to a slew of apps from developers big and small. We wanted to find out how good they were, but because they all have one thing in common, that is the experience of using the iPhone itself as the sat nav hardware, we decided to use a slightly different approach to our normal product group tests.

So while you'll find our reviews of all the sat-nav apps, it's worth being aware of how the iPhone in general performs as a sat-nav device. There are, you see, significant issues.

Using an iPhone as a sat nav

The first is that you need to position your iPhone in your car comfortably and in a safe position, so you can actually see it. The problem is that there are relatively few iPhone car mounts available, and those that we've tried are typically ungainly and inelegant.

Solutions such as the otherwise excellent Belkin TuneBase FM with Hands-Free are fine, but because they plug into the lighter socket, it's unlikely to enable the screen to sit in a position that's safe to use when driving.

Voice prompts may be the answer, but sadly the iPhone's built-in speaker is too weedy to be used comfortably; it's fine for hands-free calling at your desk, but at the volumes necessary for the spoken instructions to be heard above the noise of the engine and the tyres on the road, the audio can get unpleasantly distorted.

The iPhone also really needs a constant supply of power for all but the shortest of journeys; the big, backlit screen itself is pretty power-hungry – you don't often keep it on continuously, but you'd notice significant battery drain if you did this and nothing else. And, of course, it takes a lot of power to drive the GPS circuitry that's keeping a lock on the satellites.

Sure, standalone sat navs need this, too, but you don't need your sat nav to be able to make calls and compose emails when you arrive at your destination. Happily, these problems can be easily solved, albeit at a price.

TomTom Car Kit

The reception-boosting TomTom Car Kit may cost an eye-watering £99.95, but for our money it's an essential purchase. The locking window-sucker, which is the same EasyPort device used in the current crop of TomTom sat navs, is smart and reliable, and enables you to place the iPhone exactly where you want it.

It lets the whole thing pivot through 360 degrees, so you can flip your iPhone easily into portrait or landscape orientation. (This has the bonus of allowing the angled power cable to trail the correct way; usually, right-hand drive cars have to double back this cable.)

It also has a built-in speaker; though music sounds no more than workmanlike, spoken sat nav prompts have plenty of volume. You can use it for hands-free calling too – it includes a microphone, and does a decent job.

The big problem is the price. Given that you're going to have to add a sat-nav app as well, it's an expensive proposition; especially given that a TomTom One Classic GPS is £84.99. Even then, some problems remain. With a few background exceptions, the iPhone can only run one thing at a time, so if you want to do anything else, you have to quit your sat-nav app.

Of course, you shouldn't be mucking about with email while doing 70 on the motorway, but it's nevertheless irritating that an incoming call causes your navigation to quit. (You can always relaunch it while talking – calls are one of the exceptions that can run in the background – but it's still imperfect.)

Happily, all the apps lock on quickly on relaunch, and you can still control the iPod with Voice Control or clicks on a remote. Finally, though the iPhone's screen seems generous in your hand, it just seems a little on the dinky side in the interior of a car, and we'd be happier if the screen was just a little brighter. And if all this sounds overly negative, it's just because we want you to be aware of the drawbacks.

A good experience

The experience of using your iPhone as a sat nav, especially if you invest in the TomTom car kit, is generally excellent, and anything that means we have fewer individual devices cluttering up our lives gets our vote.

It's great to arrive at your destination with a fully charged battery, and in any case, the ability, for example, to navigate to contacts already synced to your device rather than laboriously entering them by hand is most welcome.

What's more, this is just the beginning. None of the apps here really take advantage of the iPhone's persistent data connection, or at least not yet. We're looking forward to competition driving innovation, with live traffic info, fuel prices, and even local advertising promotions.

iPhone OS 3.0's in-app purchasing should lead to useful add-on services and features, and the pace of iPhone development means we shouldn't have to wait too long.

How we tested

As well as testing the five apps here over the weeks that they've been available, we set ourselves a challenge. We defined five different waypoints around the city of Bath, beginning at Royal High School.

Then we asked the system to find a local petrol station as a point of interest (POI), which they all did. Next, we wanted to test postcode look-up, so we entered the postcode of Prior Park, a local landmark; here, some stumbled through, not supporting full postcode look-up.

Then it was off to the train station; the TomTom and Sygic apps tried to take us down a road closed except for access.

From the station, we tried an address in our contacts; some failed to parse it, and some tried to route us via a road that's closed to traffic between 10am and 6pm. Note: it would be wrong to extrapolate performance for other locations based on this sample.