big landscape and grid settings I can model fine from reference images but if I try to create a big scene I just get lost. I model in real world scale so my objects will look right.  for grid if Im trying to make a large landscape for camera animation how would I turn the grid into 1 mile? 

and if I do this does the camera settings need to be adjusted or do I use regular default settings?  any info would be appreciated. I model in imperial using inches and feet.
1)You need to set the units

2)then you can adjust the scale of the grid. 
If you need the grid to be exactly one mile long, you need to put in 330 (5280 feet divided into 16 sqares)

3)If you encounter problems with clipping you need to adjust clipping in the N panel, or/and in the camera settings