Taking a Look at the Bigger Picture


Anyone remember TerraServer? About five years ago, it was one of our higher profile
demonstration sites – over 1TB of satellite imagery data crammed into a single SQL
Server database. That doesn’t sound nearly as impressive today when I’ve got a single
500GB USB2 drive humming quietly under my desk, but at the time it was a big deal. TerraServer
lives on
, incidentally, now with a .NET web service and over 3TB of data, but
I digress…

What made TerraServer fantastic was the ability to zoom in right down to street level
from a satellite image; there was nothing neater than being able to see your own street
or somewhere you recognised as part of a satellite image. But the interface was a
little lame; you were simply pulling down static images.

This week, however, I came across a fantastic piece of software called Keyhole that
lets you browse similar images in a vastly more interactive manner. You can zoom in
or out, create virtual flights where you move around the world, even tilt the images
so that you’re viewing the terrain of a country. Keyhole adds geographical elevation
data to the images, to give them a 3D effect, and it’s truly one of the most mesmerising
experiences I’ve had from a piece of software. It caches the data so you can view
it offline, and it even allows you to fly over Mars using imagery from NASA.

Two things make this work effectively – the ultra-powerful graphics accelerator cards
that are available even on laptops these days, and (brace yourself) the use of web
services. I’ve no idea whether Keyhole uses standards like SOAP under the covers or
not, but regardless of the wire format, it’s about as visual a demonstration of a
web service as any I’ve come across thus far. Without a remote server and an HTTP-based
web service, this application simply couldn’t exist.

The only pity is that there’s a limited amount of imagery covering Europe, although
Greater London and Paris are both covered. Nevertheless, definitely something to experiment
with – you’ll get hours of enjoyment out of it!


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