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Unstability of the model in ios 9

I have tested the GroundPlane Project on iphone 5s and 7plus. In iphone 5s the 3d model placed on ground is not stable, its position changes if you move the device. Whereas on iphone 7plus its pretty accurate. Can anyone tell the reason ? Is it related to hardware efficiency of device or software issue?

I think this is expected. The main technology behind Ground Plane is called ARKit which is only available on the iPhone 6s and later.  Vuforia is probably utilizing different technology behind the scenes for the 5s which is why it doesn't work as well.