# A Review on Methods and Systems for Remote Collaboration
## 6 Discussions  
In this literature review, we identify the main applications where remote assistance is used. Table 4 represents the type of engineering applications described and utilized as case studies throughout this survey.  
To summarize the current literature review, as seen in Figure 6, we depict the trend for devices used for displaying the working context, and the development of the industry is surveyed during the periods 1999-2006, 2007-2010, 2011-2015, and 2016-2020. We observe an increase in the production of device types over all periods for all the studied technologies--HMCs, HMDs, video cameras, and smart devices and displays--with the exception of robotic devices and projectors, which are not as widely examined over time, perhaps because of their complexity and automation needs. We also observe a decrease  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Applications** & **Article Reference** \\ \hline Healthcare & [1–10,61,101] \\ \hline Industry & [13–21,30,31,36,38,40,41,92,108,112] \\ \hline Education & [11,12,26,29,34,39,47,53,95,96,99,110,111,121,125] \\ \hline Assembly Task & [28,35,37,42,48–52,57,62,63,66–73,97,98,102,104–106,109,113–117,119,122,123,127] \\ \hline Aviation & [32] \\ \hline Crime Investigation & [22] \\ \hline Maintenance & [27,60,65,74–78] \\ \hline Object Identification & [43–46,55,56,58,64,71,88–91,100,103,107,128] \\ \hline Objects Manipulation & [54,79–87,93,94,121,126,129,130] \\ \hline Design & [59,118,124] \\ \hline \hline \end{tabular}
\end{table}
Table 4: Applications of remote collaboration system.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Application** & \multicolumn{4}{c}{**Communication Cues**} \\ \cline{2-4}
**(Task Type)** & **Annotations** & **Gestures** & **Pointing** & **Eye Gaze** \\ \hline Robot Building & & [96] & [99] & \\ \hline Object Identification & [103,107,128] & [128] & [100] & [121] \\ \hline Surgery & [101] & & \\ \hline Lego Assembly & [97,98,102,105,106,109,122,127,98,113,116,119,122,127,978,113,116,119,122,123,127,127,102,115] & [97,98,113,116,119,122,123,127,102,115] & [115,116,122] \\ \hline Puzzle Assembly & [104] & & [104] \\ \hline Wiring Assembly & [108] & & \\ \hline Education & & [111] & [110] \\ \hline Industry & & [112] & \\ \hline Printer Assembly & & [114] & \\ \hline Design & & [124] \\ \hline Objects Manipulation & [126,129,126] & [126,129,130] & [120] \\ \hline Physical Task & & [125] & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Communication cues.  
in the use of discrete video cameras and displays that are integrated into HMCs and HMDs. The tendencies are towards the smallest form factor of the product; HMDs were the most dominant solution for the period 2016-2020. The interest in LCD displays and video cameras decreased from 2011 to 2015 and from 2016 to 2020. There were few identified HMDs and HMCs during 1999-2006, and the reason is that the integration and the miniaturization techniques were very incipient. We can state that the emergence of these devices, HMCs, HMDs, smart devices (tablet/phone/remote control), robotic devices, and projectors, started with a proof of concept, and the demonstration of their feasibility persuaded the manufacturing companies that the chosen solution was reliable.  
The study of the occurrence of communication cues in the same periods of time is presented in Figure 7. We can see that 20 years ago, pointing was used more often as a communication cue when collaborating remotely; in the last four years, the emphasis has been on annotations, gestures, and eye gaze.  
Overall, studies showed that, during a remote collaboration, tasks are completed better and faster when the visual workspace is shared between the participants.  
Figure 6: Number and type of devices for capturing and visualization between 1999 and 2020.  
Figure 7: Communication cues occurrences for the period 1999–2020.