Due to technological advances, affordable mixed reality devices, including both virtualreality and augmented reality, are beginning to be used to support participatory planning to better inform stakeholders of design interventions. Stakeholder participation and perception studies often utilize both qualitative interviews and quantitative techniques to gauge how a model can effectively communicate design intentions. In this paper, we examine how mixed reality enables new methods of investigating how users interact with digital models, enhancing existing techniques. We introduce a non-invasive perspective tracking system, to track how a participant explores a 3D model of a landscape intervention through the perspective of their mixed reality device. Our software provides a supplementary technique to better analyse user interaction patterns with digital models, allowing a data-driven approach to support participation studies and enable novel analytical approaches. We introduce the concept of naturally salient perspectives and show that tracking how a user frames a model during free exploration can provide new quantitative insights to support traditional qualitative participation methods