Extra Long distance tracking solution

Hello every expert here,

Recetnly I have played with Vuforia AR application (I have no source code access) with extra Long distance tracking (A4 paper, 10meter more). (Not extended tracking Mode). It works pretty well. I was wondering how it works. I am sure that this AR application is made by Unity and Vuforia. I will post here the scenario to discuss with you the possibilities to recover this type of extra long distance tracking in Unity。

1. In the very beginning, you have to focus on A4 marker at a distance around 40cm

2. Once the market is detected, an indicator let you move far from the marker.

3 At 3meter away from the marker, the AR object is displayed in front of market at a fixed distance.

From 3 -10 meter, the AR object is always there. *Even the A4-size marker is not visible anymore* (I have tried with throw away the marker)

I was wondering how it works ? I tried also with Extended Tracking Mode, even with this more it can not work at 10meters

Is there anyone who knows how it works ? or any hints ?

Thanks a lot!