Using a cartography table, we can copy maps to make an identical one. Doing so, if we lock with a glass pane one of them, if we try to modify the second one, only a single modification is possible because the resulting map will be also stated as locked.

Example in the video below

How to reproduce: (example)
1 - Create a map (scale 0/4)
2 - Copy it using a cartography table
3 - Lock one of them with a glass pane
4 - Increase the scale of the second one with a paper

Result:
You will obtain a map with a scale of 1/4
This map can be filled exploring the world
It cannot be modified (because it is stated as locked even if it is not)