An overlapping object

Question

Hi all,

I am trying to figure out how we can determine an object if there is an overlapping problem?

Basically I am in a middle of planning to develop an apps that recognise a tree, this is my first attempt having no much knowledge about android, but as a project I need to complete this task and I am hoping someone can share their knowledge about this technology.

The scope of the trees are just in a small area and basically when user activated the camera on the menu then pointing the camera (the camera here is just act as an interactive) to the particular tree, the info and details about the tree will appear on the screen, also when we moving around with camera in active mode - the 'software' will detect that there is a recognisable tree close by then the screen will pointing like an error telling us if we keep moving either direction (A little bit like the augmented reality but I do not want to involve tree recognition here but I have to take all the tree photos instead and put it in the database and also, the location of every tree) 

Also, I found out that if there is an overlapping tree behind to another tree then how can we tell the 'software' that we want the front tree not the back one? 

I presume we have to use GPS and compass? - but How do map and location interact so I got the correct object (tree)? 

Can anyone give me some ideas about this. Much appreciated.