Are you planning on hosting tournaments or just skiing with your buddies? You can spend as little or as much on this as you like. You also can get one very straight with some low stretch ropes, zip ties, duck tape, and all the measurements. Middle of the road is a portable, then drop anchor to match. Expensive is the surveyor.
Here's an example of the cheap method. We used measured sections of rope, set the anchors, then adjusted the anchors with line of sight, and remeasured. Got it done in one weekend, and it turned out well, but we weren't hosting tournaments. :) Still, old school perfect pass ran good times on it.
http://lh5.ggpht.com/_1gl9obJSimU/S47e5tL4agI/AAAAAAAACuA/qsGff12LPHk/Course%20at%20Buzzard%20Buoy.JPG