6.4 Haptic Pedestrian Model
6.4.2 Haptic Navigator
The Haptic Navigator is a waypoint-to-waypoint navigation assistance system which provides users with information about general walking direction to the next waypoint using haptic feedback and simple visual cues. A waypoint is defined as a node in the path where the user must change the direction of movement, such as an intersection (Figure 61). Typically users would view the map (paper or digital) and then try to re-orient themselves in the direction of movement by comparing the buildings or landmarks represented on the map to the features they see around them.
Figure 61: Haptic Navigator: prototype using the waypoint by waypoint navigation.
Figure 62: Field of Heading (FOH): Maximum heading range to provide accurate di-rection information.
The user is initially at an origin point, O which is at a distance d from the destination, D. The shortest path between origin, O and destination, D is stored as a line string L. The user traverses all the intermediate waypoints represented as W1, W2,. . . Wn−1, Wn before reaching the destination, D through the path, L. The way points between the origin and destination are W1, W2,. . . W n− 1 that are each at distances d1, d2,. . . dn−1,dn from each other (Figure 61). The bearing from the origin to the first waypoint is b0, the bearing from the first waypoint W1 to the next waypoint W2 is b1 and so on until the last waypoint where the bearing from the last waypoint W8 to the destination D is b8.
Field-of-Heading (FOH) is the range of the heading based on the compass value of the mobile while performing the pointing and scanning gesture. The Field of Heading Angle λ is calculated as the difference between the maximum range and minimum range of heading (Figure 62). The angle between any two paths originating from an intersection is represented as θi. In order to provide accurate directional instruction, the value of
Figure 63: Varying numbers of paths at intersections and also varying angles between them.
λ must be less than the smallest value of θi at any given intersection. We see that the number of paths originating from any given intersection is not a fixed number and can vary from point to point (Figure 63). We can also see that the values of θi vary based on the angle created between any given pair of paths at an intersection.
Using Haptic Navigator, the user scans the area by holding the phone horizontally and slowly moving along the horizontal plane. This is depicted in Figure 64 where the user holds the phone out and looks for a waypoint by scanning the area. When the user is pointing in the direction (heading, h) of the next waypoint, the user is provided with feedback both visual (colour coded buttons and distance displayed on screen) and non-visual (haptic feedback using varying vibration patterns).
We say a user is pointing in the direction of the next waypoint when the Field of Heading (FOH), created when the user performs pointing gestures to scan the area overlaps with the bearing between the current point and the next waypoint (Figure 64). There is a
Figure 64: User pointing in the direction of the next waypoint using HapticNavigator.
Figure 65: Visualising the scanning activity of a HapticNavigator user.
buffer distance of db metres that is set at every waypoint to ensure we account for the possible GPS error. Here in this example, the user is at the first waypoint, W1 and is scanning to find the direction to the next waypoint, W2. Once the user gets feedback about direction to the next waypoint, the user starts to walk in that direction and will then be alerted (via a unique vibration pattern) when he is within a buffer distance, db metres away from the next waypoint. The user understands they are now within the waypoint and have to perform the next scan to find direction to the next waypoint along the path towards the destination. The user performs these sequences of steps until they finally reach the destination, D. The user is alerted about arrival at the destination via a continuous vibration pattern when they are within db metres from the destination.
The scanning activity of the user can be stored and visualised and in Figure 65 we can see the scanning activity performed by the user during one of the walks from a given origin to a destination using the Haptic Navigator. The origin of the walk here would be the point in the centre and the perimeter of the circle here represents the destination. The bunched blue sections represent the part where the user is walking from one waypoint to
Figure 66: Visualising the accelerometer readings of a HapticNavigator user.
the other where no real scanning operation is performed here. And the other complete circle shows waypoints in the path when the user performed the scanning operation.
The accelerometer reading on the mobile device helps to keep track of the user motion and steps taken (Figure 66). The peaks in the graph represent the user walking and the sections in the graph where the value is around 10 represents sections in the path where the user is standing still and performing the scanning operation. From the graph plotting accelerometer values (Figure 66) we can note that the user would have paused 7 times during the entire trip. This data when checked with the number of waypoints, we see that it matched the 6 waypoints and origin when the user had paused at waypoints to scan the area to find the direction to the next waypoint till they reached the destination.
The Haptic Navigator provides waypoint-by-waypoint navigation assistance from origin to destination using a non-visual feedback technique. In hiking/trekking situations it is sometimes impossible to find easily identifiable landmarks making Haptic Navigator a very suitable candidate for use. The key features/functionalities of this prototype are:
• Works using the ‘waypoint-by-waypoint’ navigation assistance technique.
• Phone is held in the hand for performing the scanning operation.
• Does not require user attention while walking towards the next waypoint as they will be alerted when they need to make a change in their walking direction.
• Feedback only when pointing in the direction of the next waypoint or about arrival at a new waypoint.