Keeping the World going Around

These days we have all seen many rotating globes, but back in 1993 these were quite rare. And that was when I was asked if there was any way of adding some interest to a product called MAGI - an otherwise quite static computerised life underwriting manual.

When asked if it was possible to have a rotating globe (rather than a static map) I replied that it must be and I would look into how easy it would be.

As always, there were a few constraints:

• The underwriting manual was produced using Windows help files, so anything we added needed to be compatible with these.
• Limited time and budget meant we could not research buying an existing globe and probably the products budget could not afford it.
• Obviously, we had to be squeaky clean over copyright issues, and even if we found a globe (and could afford it) our exacting users probably would not accept it without a good deal of customisation.

The company already owned an existing Mercator projection, and this was used as the basis for producing the following 2D bitmap.

All I had to do was work out a way of wrapping a 2D image around a sphere.

Actually the maths is quite straightforward, and the globe at the top of this page is the result. What you see is not the actual end product - I have converted it to an animated gif and cut back the number of steps per revolution just to keep the file size manageable over the internet - so it is not quite as smooth as the original.

Interestingly, I had a few comments that the world was rotating the wrong way. This must be quite a common issue as, if you search Google images for 'Rotating Globe', you can still find some that rotate the wrong way.