The Spitfire’s PR, or photo reconnaissance, variant proved to be extremely successful in the imagery collection role. The camera-equipped fighter aircraft accomplished several key reconnaissance missions. For the high-altitude, highspeed area coverage missions, the pilot of a high-flying fighter kept constant watch on the rear-view mirror to make sure that a contrail did not reveal his presence. Once over the target, the pilot maintained a precise course and altitude setting to collect a wide-area view of the situation on the ground. If photo-interpreters identified an important target, such as a V-1 launch site, another mission flew in low. Those missions presented more danger than the high-altitude missions. At high-speed and low-altitude, the pilot lined up a black cross on the side of the canopy with a small black stripe painted on the wing. He had to focus in the face of anti-aircraft fire, fighters and the ground. Sometimes other sources of intelligence validated the photo-interpreter’s analysis. After they assessed that there was a Focke-Wulf 190 plant working at Marienburg, Germany, technical intelligence verified it through the interpretation of data plates from crashed FW-190s and the Eighth Air Force destroyed the factory.