Many thanks for your detailed response. It helps to understand how it works to be able to find the best workflow.
I wasn't aware that a noisy environment would be bad for extended tracking, in fact I expected the opposite to be true.
I have also found that the target image needs to be as large as possible for the first step, as smaller images that may work well for simpler examples, don't perform as well when extended tracking is enabled. I tested an A4 page with a central image about half the page size, then an A4 page with a print covering the entire page.
I have set up a Phonegap project with a number of custom examples for iOS and Android.
Two of the projects use extended tracking, and the results on Android are proving to be very poor.
On Android only...
1. The extended tracking indicator (copied from examples) starts and indicates that tracking is good.
2. The tracking is not good, and the model disappears
3. Position of the model is expected to be vertical, but in most cases shows misaligned.
Does extended tracking require the gyroscope and accelerometer to work?
iOS does perform better, but there is a certain amount of drift which I don't expect given the starting position being set from an image.
I'll continue to test the extended tracking and report back if I can make any improvements.
I am also finding that the Android app crashes quite regularly when loading assets from a server. This has been reported by my client and is difficult to reproduce locally.
Do you have any tips to handle loading examples as per your sample i.e. menu > open example > back to menu?