The workers are paying their respect to the head of the statue before putting it up onto the statue, a ceremony to pray for smooth construction maybe? ^^
Indeed, the younger generation of fans like us only knew Gundam through its anime series and merchandises, but there's a whole lot we don't know about it I believe, especially its impact to the culture of Japan and on the sci-fi world as a whole.
Respect.
Was thinking of having 00 Gundam bowing instead, but just realized that I haven't built that kit yet, ^^; so HCM-Pro Exia stands in as the youngest (newest) paying respect to the most senior Gundam. ^^
Anyway, the book was just released yesterday (July 31st) in Japan at 1,050 Yen (inclusive of tax). Interested fans please watch out for its arrival at your local book store. ^^
All images from Moeyo.