The large area imaging detector array is located where the black dot is in the middle of the bottom edge of the rectangular image. The height of the image corresponds to just over 100 meters.
The image is "developed" as the vehicle moves from left to right. In this animation, the reconstructed image is slid off to the left at the same rate, so that the detector array appears to remain stationary while the recovered image moves to the left.
Detected in sequence are: a 2 mCurie source at 100 m, then a 0.5 mCurie source at 25 m, followed by a 1 mCurie source at 50 m.