As I promised earlier on, here’s a small post with some suggestions on how to make AR apps.

When the iPhone OS 3.1 will be released (the sdk and os are now in beta), it will be possible (and approved by Apple) to overlay anything on top of the camera view, exactly to achieve Augmented Reality applications.

At the moment it is not possible to actively analyze the images presented to the user via the camera, unless using some tricks (which may not prove satisfying, i.e. take multiple screenshots of the screen), or jailbraking (or however it’s called the process of removing Apple’s restrictions) the device.

Following are some specs that most probably your application will need to use if it has to display some information based on your current location (GPS) and heading (compass).

In landscape mode:
Screen height: 320 px / 4.99 cm
Screen width: 426 px / 6.64 cm the camera view leaves some space under itself (which might come useful for some buttons/ui components), that’s why it’s not 480 px.
1 cm: 64 pixels
Camera FOV height: 34.6 degrees
Camera FOV width: 50.1 degrees

With these informations you should be able to do all kind of conversion calculations given you have for example latitude and longitude of something you want to display on screen, if you have the height as well you can use it to fine-tune the placements of all the items on the overlay view of the camera.

Hoping that this information can be useful to someone.

ciop ciop