**3. Marker-based augmented reality**

Marker-based AR uses markers (A two-dimensional pre-defined screen) that are placed in the scene and within the field of vision of the camera in order to help guide the camera pose estimation process [8]. The markers are frequently indicating to as fiducial markers because their position and orientation relative to the scenery are steady. The markers are always planar makers and commonly have powerful feature, for example, long edges, as well as, corners among black and white regions. In this technique, AR puts a powerful emphasis on the design of the marker. One of the most common kinds of marker design is square because the feature of square will allow for accurate localisation of the markers by using its four corner points [12]. Marker-based AR uses computer vision techniques in order to calculate the position and orientation of the camera relative to the marker. The virtual 3D objects can be overlaid accurately on the markers as shown in **Figure 4**. It has a primary operational principle: capture the video input from the camera, add 3D graphics to the scene and show the augmented frames as a video stream [13].

**Figure 4.** *Marker-based AR [14].*
