Where do you go when you have developed a sat-nav system that can get people from A to B efficiently? Well, you start adding extra features. For some devices this means MP3 playing, Bluetooth hands-free telephony, digital image displaying and other stuff not strictly related to the process of satellite navigation.

For Mio, in the case of the C620 (and the C620t, which comes with TMC traffic information capability), music playback, photo viewing and contact management are provided, in addition to Bluetooth hands-free.

But Mio has also come up with an innovation in its mapping data, adding 3D into the mix. This isn't the 3D ‘flyover' type view that has been available in sat-nav systems for ages, but proper elevation mapping. Plus 3D landmarks.

The elevation views are more useful than you might at first think. It is handy to be able to glance at the rendering of a complex motorway junction and know that you are doing the right thing by being on the middle layer of the motorway cake. On the other hand, it is just possible that more than a glance is needed to take the 3D image in, in which case you could be tempted to have your eyes off the road for longer than is safe.

Get the latest Dell Coupons and other computer coupons at CheapStingyBargains.com.

The 3D landmarks we are less convinced about. OK, so we now know it is possible to render the Houses of Parliament in SimCity type form and put them onto an on-screen map, but is that really necessary or just a gimmick? We're going for the latter view.

There is one other really useful feature that could easily get lost in all this 3D-ness. When you calculate a route the software produces the fastest, shortest and ‘economy' routes at once, showing you the distance and travel time for each. You select the one you want to use by tapping the screen.

This is much more user-friendly than setting universal calculation rules for trip types. If nothing else it takes account of the fact that users might want different types of route at different times and prefer ad-hoc selection.

The C620 and C620t share the same basic size and format, being 12cm wide, 8cm tall and 2cm thick. The front is all screen and the display measures 4.3 inches from corner to corner and delivers 480 x 272 sharp, bright and clear pixels.

The screen can be split into two sections, with the right-hand third offering travel information such as distance to destination and current speed, and the left-hand two-thirds offering the map itself. Maps of 22 European countries are included.

So, satnav goes 3D. We like the elevation maps but not the 3D landmarks. Satnav providers need to think carefully about avoiding ‘feature bloat' in their quest to beat the opposition. That said, we like the C620 despite its 3D landmarks.