Cartography

This proficiency grants skill at map making. A character can draw maps to scale, complete with complex land formations, coastal outlines, and other geographic features. The character must be reasonably familiar with the area being mapped. The DM makes a proficiency check in secret to determine the accuracy of the map. A successful proficiency check means that the map is correct in all significant details. If the roll fails, the map contains a few errors, possibly a significant one. A roll of exactly 20 means the map contains serious errors, making it useless.

[Complete Ranger's Handbook]