iphone 15 gps accuracy

Hello,

I have been using iPhone since iPhone 3, I bought iPhone 15 one month ago, I used 11 pro and 7 before, I just realized that GPS accuracy is changing 9-20 meters, I still use iPhone 7 and I don't have such an error, i compare both 15 and 7 side by side and 15 accuracy really worst, I also talked to expert customer service but there is no result, this accuracy is so much important for me reason of i am using Navionics navigation chart and anchor alarm app on my boat, is there anyone who has experienced this or can help? Thanks