# A Review on Methods and Systems for Remote Collaboration
## 5 Communication Methods and Cues
### Behavior Detection  
In this section, we look at studies that focused on the behavior of the human body in a remote collaboration context. [PERSON] [27] proposed a method where the helper could follow a local worker's gaze through an eye tracker and head-mounted camera worn by the worker. However, a problem with this system was identified. Users could not make eye contact, and gaze awareness was lost. To improve this aspect, a conventional telepresence system was developed in [110], based on a see-through display that gave local and remote users the sensation that they were separated only by a vertical sheet of glass. This offered the ability to make eye contact and use non-verbal communication such as gaze and gestures. As augmented reality is starting to be used more often, researchers are attempting to use it to overlay hands on a video stream. In [111], a solution is presented allowinghand gestures to be identified using augmented reality, and this method enables intuitive interaction during real-time computer vision. HandsOnVideo [112] gives the helpers the possibility to point to objects using their hands. The remote worker's hands are overlaid onto the video stream on which the local user is able to see the instructions. An improved solution of HandsOnVideo is proposed in [63], which introduces hand gestures in a 3D context and allows the remote helper to use his hands directly to gesture. A special camera is used to capture hand movements in 3D. BeThere [113] is based on a mobile smartphone configuration and depth sensors that allow two remote users to perform 3D mobile collaboration. This solution allows the remote user to perform 3D gestures in a shared environment and navigate in the 3D shared environment. In order to direct the user's attention, the system uses awareness cues such as helping hands and 3D annotations. In his research, [PERSON] [114] showed how a gesture-recognizing module could detect and recognize the gestures of a remote user. The system recorded the position and the description of the gesture and displayed them as virtual hands on the local user's display. In their study, [PERSON] et al. [115] tried to evaluate whether sharing the eye-tracking information of the local worker could improve performance during a remote assistance task. The study combined an eye tracker and a pointer and showed that the cues could enhance the feeling of co-presence between remote users. Another approach to using both the eyes and the hands was proposed by [PERSON] et al. [116] in their research. The study addressed the problem of eye fixation during a remote guidance operation. Helpers used their eyes to identify the object of interest, and the hands were projected onto the local user's space to provide instructions for the manipulation of the objects. A study by [PERSON] et al. [117] explored how shared gaze awareness impacted remote collaboration. The results showed that shared gaze information could be disruptive but improved remote coordination. SharedSphere [90; 91] is a prototype in which both the local and the remote user's hand gestures are captured and displayed on head-mounted devices worn by the users. The local user's hand gestures are captured by a video camera, while those of the remote user are captured by a hand-tracking sensor. The study in [118] researched how gaze sharing in both directions influenced collaboration and communication between two remote participants. An eye tracker module was placed on the HMD of the local user and on the display of the remote helper. Results for most of the users showed that the system improved their awareness of their partner's focus, while some users mentioned that they could determine what the next step for their job execution would be. HandsInTouch [119] combines gesture sharing with sketches in order to collaborate remotely. The study shows that hand gestures might be sufficient when performing easy tasks, but sketches together with gestures give better results when used for complex physical tasks involving objects. [PERSON] et al.