Shooting 101.
My Ballistic app on my iPhone makes the correction for shooting uphill or down hill. I have a bracket on my gun to mount the iphone and it automatically measures the angle and puts into the calculation. Also the app automatically gets info on temperature and pressure from the nearest weather stationed the internet as well a altitude from gps for the calculation.
Have made several long range hunting shots with this app, longest was 970 yards on antelope in Wyoming.