I'm in the process of creating a line of detailed trail maps for all of Korea's national parks, based on 3-4 different existing Korean maps and my own experience hiking in the parks. I've found that most of the maps out there don't have all the info I want when I'm hiking. So I'm trying to make these very comprehensive, with the hiking times KNPS recommends, point-to-point distances, shelter locations, drinking water locations, current trail closures, etc.
I've finished a few thus far---Eastern Jirisan National Park (Western half coming soon), Songnisan National Park, Juwangsan National Park, and Gajisan Provincial Park. Maps for Gayasan, Hallasan, Deogyusan, and Seoraksan are in the works and should be online within the month.
All maps are available at high resolution and downloadable from my blog, which also includes detailed reports of specific hikes and bus information for getting to and from the trailheads:
I hope you all find this useful.