12 December 2012 Last updated at 23:19 ET By Leo Kelion Technology reporter Google has released its Maps app for the iPhone, in the wake of complaints about Apple's software.
Apple controversially replaced the search giant's mapping service with its own when it released its latest handset, the iPhone 5.
The move was widely criticised after numerous mistakes were found in Apple Maps' search results.
Google's app introduces functions previously restricted to Android devices.
One analyst said it would prove popular, but added that Nokia still posed a challenge.
The Finnish company recently launched its own free maps app for the iPhone.
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Apple's mapping nightmare
When Apple announced in June that it was launching its own maps app - using licensed data and its own software - developers cheered.
But soon after it launched in September, the complaints began.
The UK's historic town Stratford-upon-Avon was missing, a farm in Dublin had been labelled as an airport and Hong Kong's Queen's Pier boat terminal was in the wrong location.
Satellite images were sometimes blurry or only showed cloud cover, and the much-vaunted Flyover facility had created surreal views of landmarks including the Brooklyn Bridge and Hoover Dam.
Facing growing criticism, Apple boss Tim Cook penned an apology acknowledging users' frustration.
It did not seem to dampen early iPhones sales, but the affair was linked to the high-profile ousting of iOS software chief Scott Forstall, who had reportedly refused to sign the apology himself.
Mr Cook recently acknowledged that the firm had "screwed up", but promised Apple had a "huge plan" to improve the app.
The firms are motivated in part by a desire to gather data automatically generated by handsets using their respective software, as well as users' own feedback.
This allows them to fine-tune their services and improve the accuracy of features such as traffic status updates.
Android's advantage Features Google has introduced that were not available in its earlier iPhone app include:
- Voice guided turn-by-turn directions, with estimated travel times.
- Indoor panoramic images of buildings that have signed up to its Street View Business Photos service
- 3D representations of the outlines of buildings that can be viewed from different angles
- Vector-based graphics based on mathematical lines and points rather than pre-created bitmap graphics, making it quicker to zoom in and out of an area.
Among the facilities Google's iPhone app lacks that are present in its Android equivalent are indoor maps, the ability to download maps for offline viewing, and voice search.
However, over time, project manager Kai Hansen told the BBC that what was on one platform should be on the other.
"The goal is clearly to make it as unified and consistent an experience as possible," he said.
Ground Truth One area Apple's own software still has an edge is its integration of Flyover which offers interactive photo-realistic views of selected cities using 3D-rendered graphics within its maps app.
Google offers a similar facility via Google Earth which is promoted in its main maps app, but involves switching into a separate program.
However, for many users the key feature will be the level of accuracy that Google offers.
Since 2008, the firm's Ground Truth project has mashed together licensed data with information gathered by its own fleet of Street View cars and bicycles.
The images and sensor data they collect are analysed by computers and humans to identify street signs, business names, road junctions and other key features. To date, more than five million miles (eight million km) of roads across 45 countries have been covered.
This information is supplemented by the public filing their own reports. iPhone users are encouraged to do likewise by shaking their handsets to activate a feedback function.
"Google Maps, as much as any other map application, lives from the data that we receive," Mr Hansen explained.
"If a road is closed for the next six months, or a road was opened two days ago - these are things that somebody who lives next to the road immediately notices, but if you're not in the area it becomes hard to know.
"The more we can give you the ability to let us know about things that are changing on the map, the more other users will benefit from that corrected information."
He added that once operators verify these reports, changes can be made "within minutes, rather than hours".
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Making money from maps
Google says the new iPhone app does not feature advertising - unlike some promoted results in its web browser map pages.
Suggestions for specific locations - such as restaurants or shops - are instead based on a user's search history and other information gathered from their Google account.
Google will cover some of its costs by charging certain third-party developers who embed its maps in their products.
But for now, the biggest benefit is likely to be brand loyalty, helping to drive users to its main search engine, which is profitable.
That may change in the future.
Earlier this year, Google's mapping chief Brian McClendon told the BBC that "local advertising is going to be a critical part of any mapping or local search experience" in the long term.
Apple is also seeking to improve its own data through user feedback, but risks having less to work with if iPhone users switch to another product.
There had been speculation Apple would reject Google's app from its store for this reason.
But since iPhone sales are at the heart of Apple's fortunes, it may have felt it had more to lose than gain by allowing rival Android handsets to offer a popular app it lacked.
'Neutral' Nokia Google's launch will also have consequences for Nokia, which recently launched its own Here Maps app on iOS.
The European firm's location division is decades older than Google's, and also has a strong reputation for accuracy.
However, the Here app has had a shaky start with many users complaining about problems with its interface - a consequence of it being written in the HTML5 web language rather than as a native app, specifically for the iOS system.
Even so, one telecoms analyst said it would be premature to write the company out of the game.
"I'm not convinced Nokia as a brand for maps will become a big thing in the consumer consciousness, but what I think is going to happen is that more businesses are going to quietly do deals with it for maps," said Ben Wood from CCS Insight.
"Because of the issues that Apple had, people have suddenly understood the importance of quality mapping and they may also say they don't want to go to Google as all of the data then runs through the search firm, strengthening it as a competitor. Nokia is more of a neutral partner.
"Amazon has already done a deal with Nokia on its Kindle tablets, and I wouldn't be surprised if RIM's new Blackberry devices and Facebook follow."
