Hello,
I'm a passionate real time graphic developer and it seems your project fits my skills and experience.
A bit about me, I have more than 10 years experience in simulator industry building Image Generator for various projects ranged from flight simulator, armored vehicle simulator to commuter train simulator. The technology used for those projects also varied but mostly my work is to extend open source or commercial graphics engine with features that required for simulation purposes. For example, I have developed virtual globe terrain rendering for flight simulator, shaped cloud rendering, weather system, day and night transition, and atmospheric scattering.
For your project, I have used OSG in the past but haven't tried the OSG earth yet but I'm sure I won't have any trouble using it. I also proficient in C++, OpenGL, Cg Shaders / GLSL, and familiar with graphics engine codes if you need to change or add some features that the engine doesn't provide. For example, I have modified Ogre3D code for hardware occlusion feature and Unreal Engine 4 plugin camera projection that required for a project.
I think I won't have difficulties for the visual effects tasks because I've mostly implemented them. The interesting point is the 3rd step. I think we could implement some kind of ray cast to the terrain and change the itinerary based on the result.
It's great to have a project like this that makes me excited. Feel free to discuss or ask me anything.
Thanks.