Geography Reference
In-Depth Information
Fig. 10
The basic camera view
On top of that layer is the layer that holds all the augmentation to the appli-
cation. It is called an overlay (Fig.
11
).
7.3 Creating an Overlay
Any image or text or any other object that can be drawn may be used as an overlay.
An overlay is not restricted to one object per layer, it can hold as many as space
allows on the screen. And there can be many overlays on top of each other
organised by priority.
For this particular application the overlay is an image of a red bubble to indicate
there is an object. This can be drawn on the overlay layer at any time and in any
position and in multiple positions.
This overlay is essentially the same as the map view overlay except the map
overlay is planar and this augmented reality overlay is relative to an egocentric
view on the geography. Figure
11
illustrates the difference.
7.4 Handling the Device Sensors
To handle the sensor events on a smartphone in a CPU-efficient way they need to
be implemented efficiently, and run in the main user thread. On Android, it means
they need to be handled in the main activity. They cannot be running as a service
or as a background thread. All the other calculations and processing can be done in
