Hi Mimi! First of all, “ground” is uncountable, so you need to say, “rugged ground.” This means ground that is very rough, uneven, irregular, or rocky. Rugged can be used to talk about the general condition of a person or thing. “Ragged” is close in meaning. It normally refers to an edge that is rough and uneven, such as “a ragged dress.” A good synonym is “tattered.” That tells us that the hem and the ends of the sleeves are irregular, torn, and in bad condition. You couldn’t say, “a rugged dress.” I checked the Oxford English Dictionary, and it said that “ragged ground” is possible, but it sounds strange to me. “A ragged cliff” sounds good, because cliffs have an edge.

hi Mimi. I'm learning English here. Do you want to practice more with me? I am interesting in Japanese culture. that's why I asked. looking for your feedback.

Note that both ‘ragged’ and ‘rugged’ have multiple meanings. In the case of ‘ground’ really only the ‘uneven’ meaning of ‘rugged’ makes sense. The ground is rugged. (Uneven) My bicycle wasn’t rugged enough to survive the journey. (Sturdy) ‘Ragged’ is used for a line or edge - not straight or smooth. Borders between most countries are ragged, but the US and Canada have a long portion of border which is a line of latitude.

They are very similar when used to described the landscape (to the point that I doubt anyone would notice) but more generally rugged tends to mean something more like ‘durable’ or ‘strong’, so in your example you are describing the landscape as perhaps a little old or worn down but still going strong. Ragged would be used to describe something that is not in its original condition and not fairing very well, is missing bits or is perhaps now an unusual shape. In terms of your example it is probably describing the ground as jagged, irregular or maybe difficult to cross. eg. Look at that magnificent old rugged castle and that ragged shack next to it.

Thank you, Tom!