calculating landing speeds at high altitudes

I don't know of any airports at 30,000 feet, the ramp workers would all be dead from oxygen deprivation and very frozen. For the sake of discussion, you would have to land above the stall speed at FL300 which would probably be around 240 KIAS(guess). You would have all sorts of problems. Speeds are complicated and aircraft type specific. They're set by the manufacturer during flight testing and depend of weight, temperature and pressure. I'm sure they're basic charts that they start with but this information is hard to find and very complicated math. Within the normal range, 0-10,0000 feet MSL, landing speeds remain the same. The true airspeed increases thus requiring more runway. The pitot tube basically measures air molecules at a given speed. The wings require X amount of air molecules to pass over them to create enough lift for flight. 160 KIAS(X amount of air molecules) is the same at 0 feet or 9,000 feet but at 9,000 the aircraft has to pass thru the air at a faster rate(TAS-True Air Speed) to achieve this. At 0 ft. the TAS is about 160 knots. At 9000 ft. the TAS is about 183 knots. Both using 160 KIAS.