the clay bar like YeuEmMaiMai says will get rid of some of it... for really tough water spots on auto glass, I've had to get a product designed for that - lots of glass polishes out there. Vinegar or lemon juice can get rid of water spots (need something acidic), but the products designed to do it have worked better for me.
I had terrible hard water spots when I bought my forester XT in 2016. I tried everything with no success. I lived with it until I had it tinted this past summer and asked them if they could get rid of them. Their detailer got 95% off and it makes a huge difference and looks so much better! I think he used some sort of glass polishing compound with a powered buffer (something I did not have, I was just using elbow grease). Maybe try that?
before I installed a kentico water softener for my house, I had a RV filter on my outside faucet because our water was as hard as a rock... that will help with spotting of the car when you are washing it if the water is not treated.
Wow, that is flat!! Nice picTried out 'Last Cut Compounding Glaze' on the the hard waterspots on two of the windows and the side view mirrors and it removed alot of the spots. I need to work with it some more but I'm hoping it takes the rest out.
Took the Outback up to the highest point in Nebraska this morning - Panorama Point.