The world's top five vendors of portable navigation hardware more than doubled their shipments in the second quarter of 2007 compared to the same period a year earlier, according to a new market survey.

Research firm Canalys reported that the leading vendors all saw substantial market share gains in Asia-Pacific, EMEA and North America.

Garmin and TomTom remained the world's largest vendors of portable and handheld GPS navigation devices, with close to half the global market divided almost equally between them.

A relative newcomer, veteran Taiwanese PC maker Mitac's Mio subsidiary, took third place in the market with a 9.2 per cent share.

"Mitac's GPS has become a key growth driver after being launched in late 2003," wrote analysts from MasterLink Securities in a recent report. "We forecast Mitac's 2007 handheld GPS shipments to grow 76.6 per cent to 7.95 million units."

MasterLink's forecasts show Mitac's 2008 shipments rising a further 50 per cent to 11.9 million units. However, Mitac's core desktop and server business is expected to shrink, MasterLink warned.

In addition, shipments from the world's fourth largest mobile GPS vendor, Magellan, are rising fast and threatening to catch up with Mitac. Magellan enjoyed 548 per cent year-on-year growth in the second quarter.

"It is difficult to point to another part of the high-tech industry that is so dynamic and growing as fast as the navigation sector," said Chris Jones, vice president and principal analyst at Canalys.

"With the current market growth, the still huge untapped potential, rapid hardware and software development, and the number of players vying for a share, you can understand why there has been so much merger and acquisition activity and interest in this business recently."