Q: "This person is skiing." Does this mean that "this person is on the snow"?
A: yes

Q: "The skateboarder in the white shirt jumped into the air." Does this mean that "The boy is outside."?
A: it is not possible to tell

Q: "A man and a woman are riding bikes on a street." Does this mean that "The people are sitting at a a table."?
A: no

Q: "A man stands on a sandy ground holding a spear." Does this mean that "A person stands on a sandy ground holding a spear."?
A:
yes