You've probably heard of Google Earth. You may have even installed it and spent hours wistfully bouncing around the globe, looking at your house from space, and generally living the life of a superhero. If it wasn't free, we might complain that Google hasn't put an awful lot of effort in - like SketchUp, this was purchased from an outside source.

But since the former Keyhole became Google Earth, it has seen massive improvements. Terrain modelling, 3D buildings, and a huge range of geographical information has been added, and the detail has increased exponentially. There's also a lovely new interface this time, far in advance the previous version.

The most significant addition in this version is support for Keyhole Markup Language, an XML offshoot that promises to dramatically simplify the process of adding data to the globe. It brings with it support for extra overlays such as topographical maps, and the import of textured building models, a feature sorely lacking from previous versions.

All those delicately modelled maps and textures aren't going to come cheap, which is why the new relationship with SketchUp fits so well. You're free to create whatever models you like and place them upon the surface of Google Earth, and you can share those of others via the 3D Warehouse hub.

There's still some work to be done on increasing the photo resolution, but with over a third of the world's rooftops now covered at one pixel per metre resolution, Earth's detail is astonishingly high. The same can be said for terrain - a huge proportion of the world is lumpy and realistic, but there are noticeable chunks of land that definitely shouldn't be so flat.

No doubt rolling updates will keep increasing the detail and depth of this latest version, and the increasing number of user-created add-ons should ensure that this stays relevant. Whether you pay out for the Plus version - which offers little more than GPS functionality and better annotation - is another matter. Alex Cox