The game is officially on! The picture has been posted on Bad Robot's Twitter Account...
Few days ago I told you that I expect them to release an official picture from the set when they start filming. May 16th will be a day long remembered. Begun the new trilogy has!
I love the little hint with the sand on the clapperboard. They're filming in Abu Dhabi, not Pinewood as some other rumors suggested.
— Bad Robot (@bad_robot) May 16, 2014
Here's an article posted by the GulfNews yesterday confirming that filming will start on Friday May 16. Looks like they were right. They also revealed that according to their source filming will last for 2 weeks:
A person with knowledge of the film confirmed to tabloid! exclusively that filming will begin on May 16, contrary to several reports stating that it began on Tuesday.The source added that filming would last for about two weeks, bringing the duration of the Abu Dhabi desert shoot up until the end of May.Filming in the UAE is likely being supported by local production company twofour54, most recently responsible for the filming of action flick Fast & Furious 7 in the capital city. Production company twofour54 are also the local production partners for Bollywood film, Bang Bang.
So their source was right about the start of filming so I guess the 2 weeks filming period has to be considered very probable.
Just a slight clarification on the letters and numbers on the clapperboard:
AL40 - name and number of the shot (let the speculations begin)
N(D 0.)6 - filter of the lens
5.8 - lens aperture
36 - number of the scene