Campsites and onsens in Japan

Greetings

I am back with another question, this time it is about campsites and onsens. I found a few good sites detailing these two but this one seems to be the most useful

https://www.google.com/maps/d/viewer?mid=1ZBVjXbJKXFgt7AFBFQlSn5Zx3to&...

My question is that how reliable is this map? Any experience?
Thanks.

Around 70% I guess.
BC, although icons locating are mostly right,
but no publishing(collected) date(YY/MM/DD),
so latest info are no evidences mostly except with URL(link) to official/related web.

Open Google MAP search by,
Campsite : キャンプ場(camp-jo)
Onsen : 温泉 (onsen)
free/not free(---Y) : 無料(muryo)/有料(yuuryo)(---円/Yen)
Road side station : 道の駅(Michi no eki)

These are not free campsites or free onsens.

Most of them are Michinoeki, which is some kind of farmers market with large parking lot. Some people park at night and sleep in the car when the markets are closed, and in some case it is allowed, but in general it is not welcomed. At least you are not allowed to put up your tent. Free campsites are very rare in Japan (is it common in your country?). If it is really campsites, there should be some works and expenses. Campsites normally take 500-1000 yen per person if you have your own tent.

As for onsen, there are some free one, but it is also exceptional. Of course someone must take care of onsen, and there should be some kind of expenses. I am not familiar with the area you posted, but I googled Shima onsen yu no izumi and found that there were a free onsen (called in Japanese, No-Yu), but it seems to be closed.

https://konyoku.tvlplus.net/repo/gunma/yunosen.html

Most onsen take some charge, from 100 yen to 3000 yen, and I think 300-500 yen is the usual fee.