At that size the only likely candidate is the European Hornet, vespa crabro.
The wing shape and reddish thorax are a match, but yours has a darker abdomen ... ???
http://en.wikipedia.org/wiki/Eastern_Cicada_Killer
While they may be frightfully large[2], female cicada killer wasps are not aggressive and rarely sting unless they are grasped roughly, stepped upon with bare feet, or caught in clothing, etc. One author who has been stung indicates that for them, the stings are not much more than a "pinprick"[3]. Males aggressively defend their perching areas on nesting sites against rival males but they have no sting. Although they appear to attack anything which moves near their territories, male cicada killers are actually investigating anything which might be a female cicada killer ready to mate. Such close inspection appears to many people to be an attack, but the wasps rarely even land on people