text: I was looking at https://www.hkmaps.hk/viewer.html and selected the "1975.1" map. Now after looking into this deeper, I think the "year n" maps on that website actually means "latest map available by year n" instead of "maps drawn on year n" as government map tiles don't update yearly. Looking at https://www.hkmapservice.gov.hk/OneStopSystem/map-search?product=OSSCatB&series=AJ , I believe I was actually looking at maps from 1969-1974, which should be the most up-to-date ones we can use. As stream geometries are dictated by valley geometries which rarely change, I think 60-year-old maps are still accurate for mapping.
  
  The main blocker is that I am extremely unfamiliar with how I can overlay custom images onto editing software. Also, the government maps available for download linked above are not seamless, so one must manually crop the images before using it.