Have a look at my post HERE for details on getting a real-world heightmap off of NASA’s LP-DAAC satellite, it’s free as long as you add a line to your credits saying you got the data from them. 
Have a look at my post HERE for details on getting a real-world heightmap off of NASA’s LP-DAAC satellite, it’s free as long as you add a line to your credits saying you got the data from them.