When I sat down on the large central lawn of Duke University's East Campus to capture students painting the big wooden bench in front of their dorm, I knew I would have to work a lot from memory. They kept moving around. I might have 20 seconds, if I were lucky, on any given pose for each figure in the sketch.
So I worked fast, and since each figure is captured in the spot they were then, but the other figures were from moments earlier or later, this exact arrangement of the figures never occurred. That's one of the odd things about this kind of sketch - it's a scene stretched over time. Like a novel written from different character's points of view chapter-by-chapter; it's all the same story, but the figures move through it one at a time, never quite all at once.
This sketch is also featured at our sketch and photo blog about Durham, NC - "Top of the Triangle"