Supposedly, 100 Cartography is required to decode a level 5 map, according to this page.
However:
Currently, 100 Lockpicking is required on our shard to pick a level 5 chest... and 0 Detect Hidden is required.The Lockpicking and Detect Hidden skill requirements are as follows*:
Level One: 35% Lockpicking
Level Two: 80% Lockpicking OR 50-60% Lockpicking and Detect Hidden required
Level Three: 100% Lockpicking OR 70-90% Lockpicking and 40-60% Detect Hidden required
Level Four: 80-90% Lockpicking and 50-60% Detect Hidden required
Level Five: 95% Lockpicking and Detect Hidden required (being at 100% really helps though)
In February of 2000, http://web.archive.org/web/200003121042 ... easure.htm, we see this:
So if we're following these pages on cartography requirements, then you either need 95% detect hidden to open a level 5 chest, or you can do it with 90 LP and 60 DH.Skill required to open a treasure chest
Map Level Lockpicking only Lockpicking & Detect Hidden
1 35 LP --
2 70 LP 50-70 LP and some DH
3 80 LP 70-80 LP and 40-50 DH
4 90 LP 80-90 LP and 50-60 DH
5 100 LP 90-100 LP and 60 DH
Additionally, in both links, we are told that 10-15 monsters spawn upon digging up a level 5 chest.