If I understand you question correctly...
Some things - especially horizontal things - can be/exist in a place so that you could use the verb ligga (lie). People don't usually exist horizontally on the ground, so translating ligga with 'be' would sound very strange to me. The person is probably truly lying on the ground, maybe in front of a bulldozer in order to stop the construction of a bypass.
I'm not sure if i understand well, this is the kind of phrases that you would say to a pilot of an airplane that has to supposed to being flying at the moment, for example? or something that is supposed to stay in the air (or in the water) all the time like a fish or a bird?
Perhaps I wasn't being bery clear. What I mean is that the sentence "Varför är du på marken" is grammatically flawless, but it's not a good translation here, where focus is on lying on the ground. You wouldn't say the ligger-construction to to a pilot, you'd go for står instead with wheeled things.
Does that help?
Native English speakers (I'm not sure if you are) make this mistake all the time. "Laying" is actually a transitive verb. You might lay your head on a pillow, but you do not lay on your bed or lay out in the sun. When you are lounging or reclining, the correct verb is "to lie" or "lying." This almost turned into an argument at a daycare I once worked at. The teachers were always telling kids to "lay down," which is wrong. When I said "lie down," people would correct me. Some might say this falls into pedantry, and although "lay" is used colloquially, they really are two different verbs.
Hm, I never knew that before. I'm a native english speaker (I'm from the United Kingdom), and I never realised that there was a difference between the two. Thank you for the information :)
I just looked it up, and a good/simple explanation is this (for anyone else wondering the same thing):
Lay is for objects, or maybe parts of your body, e.g. you lay a book on a shelf, where-as to LIE refers specifically to a person becoming horizontal, i.e. lying on the ground or on a bed
You're welcome, and thanks for being gracious about the guidance. The issue becomes even trickier when you consider that the past tense of "lie" is "lay." So "I lay awake in bed all last night" is correct. Maybe that's where people get confused. Not sure! It became a pet peeve of mine when somebody tried to tell me I was wrong. :)
Tack så mycket! There's such an overlap in dictionaries' translations for the three words I guess one has to learn to distinguish between them by exposure/experience, something like with prepositions ... Incidentally, if "på jorden" is "on the soil", would a good translation for "himlajorden" in the song Änglamark be "heaven on earth"?