AR Location-based for Android

This AR app generally show where things are in the real-world by indicating where the app thinks they are over the camera view when the user holds the phone up and moves it about.

Theoretical base

Augmented Reality will transfer real coordinates system to camera coordinates system. In AR Location-based, the real coordinate is [Geographic coordinate system] (https://en.wikipedia.org/wiki/Geographic_coordinate_system). We will convert the GPS coordinate (Latitude, Longitude, Altitude) to Navigation coordinate (East, North, Up), then transfer Navigation coordinate to Camera coordinate and display it on camera view.

GPS coordinate to Navigation coordinate

There are two steps:

1. Convert GPS coordinate to ECEF coordinate (Earth-centered Earth-fixed coordinate):
2. Convert ECEF coordinate to Navigation coordinate

Here is PDF file about convert GPS coordinate to Navigation coordinate.

###ENU coordinate to Camera coordinate

To convert ENU coordinate to Camera coordinate, we will multiply camera projection matrix with ENU coordinate vector, the result is a vector [v0, v1, v2, v3].

Then x = (0.5 + v0 / v3) * widthOfCameraView and y = (0.5 - v1 / v3) * heightOfCameraView.

ENU coordinate vector: [n -e u 1]

Camera projection matrix is result of Original camera projection matrix and Rotation matrix multiplying

Original camera projection matrix:

Rotation matrix: you can get this value by using Android sensors