Actually JDAMs are guided by the U.S. satellite Global Positioning System or GPS. They are fire and forget, and don't have to be "painted" by a laser. (IE it is NOT laser guided, they are guided by GPS). They are also much cheaper than a laser guided bomb, (a conversion kit to transform a "dumb bomb" into a JDAM costs a little over $18,000), although they aren't quite as accurate as a laser guided bomb.