Rosencrantz
Very well known Exeweb poster
But apart from that...Having read this post and looked at the photo, i realise I know more about building than i thought. For instance I know what 'modular building construction is. i.e. the factory prefabrication of a building by constucting individual elements or 'modules' that can be transported in completed form ready to be connected to each other on site to create the whole building. Although I don't know about the construction industry my experience as a cabinet maker working on high end domestic and commercial fitted furniture, means I am aware of the huge cost and efficiency benefits, of being able to fabricate things in an environment that you have complete control of and easy and close proximity to all the tools machinery and supplies required for the job. I can also see the benefits of immediately (within a day or two) having a whether proof building that trades can start work on first and second fix operations straight away. I can also see that although they may be the same shape, an element of a modularly constructed building and a portacabin are completely different things.
Whilst I don't know the processes, I also understand what 'ground works' means, i.e. the preparation and levelling of the ground, piling, laying of foundations and construction of footings for intended building. The positioning and laying of water supply, sewage and drainage infrastructure, electrical conduits and any other underground cabling. Which is pretty much exactly what I can see in your photo. What were you expecting to see?