what is the exact definition of footprint

hi everyone, we re working on a project in Turkey İstanbul in which we will be applying for this credit. But we re having a hard time on deciding what the building footprint is. we have placed concrete water tanks on the basement floor and covered the top with vegetation as a continious part of the vegetated open grid. so my concerns is that; do these water tanks count as a part of the building footprint or not? and if they do; does the vegetated space over them count as a roof top? Thank you in advance