Globe Positioning System

GPS (Globe Positioning System)
In typical fashion, my next project is shaping up to be a very ambitious one. I know what I would like to create, but getting there will require a significant amount of learning on my part. I know someone could probably do this job faster and more efficiently than I could, but thats not the point. I'm really excited to start this project and come up with solutions to all the little engineering issues that come up as well learn new solutions and technologies to make the project even better.

I would like to create a rig that will take a 12" diameter globe and mechanically rotate it through degrees of latitude and longitude until the GPS coordinates or city entered by the user fall under the red laser pointer aimed at the globe.

At this point in the brainstorming phase, there are three areas that I will be aiming to problem solve:
-Mounting the globe with the desired degrees of freedom
-Precision movement
-User input

Globe Mount
I found a globe available on the market that has just the right kind of mounting system needed for this project. Its called a wonderglobe and it has a clever means of rotation. I could try to describe it, but it would be much easier to show it:

The problem is the globe is only sold in 6" versions, way to small for me to fit all the necessary electronics inside. Looks like I will have to custom make the mounting system which shouldn't be TOO hard, but will most likely be very time consuming. I think I'll be making friends with someone with a 3D printer in the near future.

Precision Movement
In order to have the globe be able to go to a single city rather than a general area on the surface, the project will require a means of moving the globe at very high precision. Ideally, I would like to have a high-resolution stepper motor (1000 steps = 0.36 degrees per step) with a rotary encoder, but since I will need two (one for latitude and one for longitude) and they are really expensive, I may have to find another solution like a hacked servo that allows for 360 degrees of rotation.

User Interface
How will the user be able to input the city or coordinates? How will I put all of the cities of the world at the finger tips of the user. While perusing World Maker Faire last month, I saw a great shield that allowed an arduino to be connected to an android phone as a controller for the arduino's outputs. The table rep only had it selecting colors of an LED and other simple things, but it could probably be made to have the user select from a list of items like, oh, i dont know... cities? I shouldn't have much trouble finding a data table equating the cities of the world with their GPS coordinates. 

I have never used a 3d printer or even a stepper motor nor have I dabbled in android programming. This should be fun. Once I move to my new apartment and settle down I'll be able to start working on this project in the next month or two and will start updating the blog section of the site with latest developments. Thanks for reading!