Every so often an application arrives on the Internet that takes your breath away. Google Earth is such an application.
Using satellite photographs taken over the last three years Google has stitched together a complete image of the Earth.
A globe which lets you zoom in with every increasing detail until you can see individual buildings, gardens and even cars.
And when you get down to ground level you can tilt the entire image into a relief view so that mountains rise high above you, and seas spread out before you.
And the cost of all this - nothing. Just go to http://earth.google.com and download the software.
Developers can even add their own data - from earthquakes to real- time bus tracking.
The only disappointment is that the whole earth is not covered to the same detail. Birmingham is split in two.
Solihull and the West are available at the highest 1m resolution. My daughters had great fun trying to pick out their school-friends' gardens, and I even spotted my car in its old parking space.
Central Birmingham and the East though is only available at 15m resolution, you can make out the Cricket Ground and the built up areas, but not individual buildings.
Our house lies almost exactly on the border; Google kindly drawing a veil of privacy over our garden.
At one level Google Earth may just be a form of Geography porn, like the Earth From Above exhibition, somewhere to just ogle the weird and wonderful landscapes of this Earth. But Google Earth could have a far greater impact.
As one developer put it "Google Earth brings to everyone the growing ability to sense in a very visceral way our spaceship. Millions will be able to FEEL our precious earth".
Quite ironically, in the same week as I was exploring Google Earth I was spending my days at Sight Village.
This is an annual national exhibition, in Birmingham, for visually impaired people, showcasing the latest resources and devices to help them live their lives.
Everything from speaking kettles to radar canes and talking PC screens.
Although research is going on into how computer images can be converted to speech, the delights of Google Earth could be many years away for visually impaired users.
More worryingly, though, most of the current Internet is still very hard for blind users to access.
I'm sure many of you are aware of the steps that web sites ought to take to be more accessible - and if you aren't aware and own a web site you need to find out.
The one message I took away about web accessibility though was the importance of the "skip to content" link - a simple but vital tag that lets a blind screen-reader user jump over all the navigation and adverts at the top of your web page and get straight to the real content.
So please, if you own a web site try and do just one thing this week - get a skip to content link installed.
It may not register on the global scale, but it will make your web site a lot more accessible for those who may never see Google Earth.
* David Burden runs his own technology and marketing consultancy, Daden Consulting. Past articles and other musing can be found on his blog at daden.co.uk/blogand he can be contacted at firstname.lastname@example.org.