# Mixed Reality: A Reconsideration Based on Mixed Objects and Geospatial Modalities
## 3 MR: A Reconsideration Based on Mixed Objects and Geospatial Processes  
MR was initially introduced by [PERSON] and [PERSON] [9] and [PERSON] et al. [14], in an attempt to classify display equipment visualizing mixed environments i.e., environments containing both real and virtual objects. The aim of their work was not to analyze the term MR, nor to provide exact specifications or scientific documentation on it. In contrast, they widened the term so much, considering it as the space between reality and virtuality, naming it as the well-known until today \"RV Continuum\" shown in Figure 2.  
Since then, MR and the RV-continuum have faced broad recognition in the research community; however, there are still misunderstandings and even confusion with respect to the exact differentiations between MR and AR or VR [27]. Microsoft [8] extended the application of MR beyond displays to include environmental input to computers and form the so-called perception. Perception, according to Microsoft, encompasses critical environmental features of conventional reality that may be computerized via sensors and input devices. Such features are the position of a person, the borderlines of real objects and surfaces (object recognition) captured in real-time. These are then blended with virtual objects and the real world to enhance human-computer interaction (HCI) in an MR experience as a result of the interactions between computers, humans, and environments, as shown in Figure 3[8]. Figure 2: A representation of mixed reality (MR) and reality–virtuality- (RV)-continuum. From the abovementioned, the authors pay special attention and structure their efforts and contribution around the MR ecosystem, to geospatial technologies able to implement perception of critical environmental features and subsequently enable human-computer interaction. Specifically, we realize the importance of digitally recognizing the real objects of a scene, their position in three-dimensions as well as their coexistence and interaction with other real or virtual objects. It is likewise important is to digitally recognize the terrain by constructing the DSM/DTM upon which interactions will take place. The principal component to achieve MR, according to our proposal presented herein, is the Mixed Object. The Mixed Object was initially introduced in 2006 by [PERSON] and [PERSON] in their proposed model of mixed interaction [8], which focuses on the linkage between the physical (real) and digital (virtual) worlds. As a result, a Mixed Object is composed of a set of physical properties linked with a set of digital properties. For the digital properties to be generated, input and output linking modalities are required. The term linking modality corresponds to an interaction technique, which was defined in [PERSON]'s modality theory [28] and was applied by the aforementioned in multifeature systems such as multimodal and multimedia user interfaces [29]. A linking modality m is a pair (\(d\), \(l\)) and is expressed as the coupling of (a) a physical device \(d\) that acquires or delivers information, with (b) an interaction language \(l\) that defines a set of well-formed expressions that convey meaning. Figure 4 illustrates the creation of a Mixed Object as the result of the linkage between a set of physical properties and a set of digital properties. An object input device (\(d_{o}^{i}\)) acquires a subset of physical properties and an object input language (\(l_{o}^{i}\)) interprets them in terms of digital properties. Based on the latter, the object output language (\(l_{o}^{o}\)) generates physical data, which are translated into perceivable physical properties thanks to the object output device (\(d_{o}^{o}\)) [7]. A faithful application of [PERSON] and [PERSON]'s considerations, employing contemporary geospatial technologies, is presented in Figure 5. We identify two input linking modalities that lead to the development of a digital object, herein defined as the Mapped Object.