Is there a standard way to let users rotate objects?

I'm currently working on a map application, which allows users to create differently sized polygons on a Google Map and manipulate them. One such manipulation is rotation, and I'm having trouble figuring out how to give the user effective controls to rotate a polygon. Right now, I'm using a slider that pops up over the polygon that can be dragged left or right to rotate the polygon clockwise or counterclockwise, but this doesn't give the user fine-tuned control, and can be difficult to use at times. Is there a standard for controls for rotating polygons (or objects in general)? What is generally used in this type of situation? Thanks!