Let's say I have a vegetation raster that indicates the density of forest all over the world. I also have a shapefile that contains the admin boundaries of each country in the world. The easy part is to make sure the grid cells are within the country boundary, but what I want to do afterwards is to create a separate polygon boundary that will surround the region in question. It is best to do it dynamically based on a certain density threshold, that could vary from country to country. I haven't exactly figured out how to handle that yet, but once I do, how would I go about encasing that data within a polygon that can be saved as another shapefile. I have attached an image of what I want the result to look like. 
So after a threshold is determined, a polygon will be drawn around the area as tight to the boundary as possible, excuse the freehand above, and then output it as a new shapefile. Is this possible and any ideas on how it can be done? Would using Model Builder be feasible to create a tool that would take the density shapefile, boundary shapefile, and threshold value as inputs to produce a polygon?
