Find set of latitudes and longitudes using user's current latitude, longitude and direction of viewing an object

Question

I am building an Android application based on Augmented Reality. The main idea is when user opens up my application, by default device's camera starts in preview mode. Based on user's current GPS location and the direction in which user/camera is facing I want to calculate which are the set of latitudes and longitudes in the range?

Following image explains my scenario very well. I have full set of latitudes and longitudes as drawn all black spots in the figure. Now suppose user is at the center of the circle. Also considering that he is viewing in North direction. If we consider an angle of 45 degree towards North direction. I want to get set of latitudes and longitudes which are coming in this 45 degree viewable area.

I am able to get the direction in which user's camera is facing. I am also able to find user's current GPS location. I have full set of latitudes and longitudes stored in my SQLite database. Now I want to calculate is the set of latitudes and longitudes in which user's device camera is facing.

I hope I have explained pretty well here. Its bit urgent if anyone can help on this.

Thanks in advance.

Answer 1

To obtain the viewing angle, you can use as an approximation the Camera.Parameters getHorizontalViewAngle() method. Let's call it alpha. You also know the bearing of your device from its point of view to magnetic North, let's call it beta.

From there, within a given radius, iterate through set of database locations, compute the bearing from your position to its, and check if it is inside the interval [beta-alpha/2, beta+alpha/2]

If you're not really on a rush into this, I would suggest to take a look into Mixare, its an open source framework which deals with location and AR.

Answer 2

you can check the code of mixare, an augmented reality browser released under the GPLv3. The repository is available at: http://github.com/mixare/mixare

There are a lot of details you have to take care of, starting from the fact that the Field of View of the camera is only programatically available since version 2.3 (IIRC) of android. You find these and lots of others in the compatibility class.

HTH, Daniele - mixare team