Minecraft: Edition

Here is a quick video guide on how to get the achievement in the tutorial world. I would recommend playing on peaceful when going for this.

It took me about 6 hours to complete it since I was alone to do so. Make sure to keep track of where you go and not let any blurry spot on the map because it might be long trying to figure out the spot you're missing. Also if you do it in a tutorial world or if you've generated a classical size map you will need to log out and before you load the map again you wanna hit the "more options" button. Then use the LB bump of your controller to move to world options and make it a medium size and load map. This should make your map a 3x3 like you need for this achievement. :)

This achievement is not difficult, but incredibly time consuming, the more people you have helping you out, the faster this will go (you all will get the achievement).

The achievement requires you construct 9 maps and fully explore each one with a different, adjacent part of the world.

Constructing a map

A map is constructed using 8 pieces of paper and a single compass in a crafting table. Paper is easily obtained using 6 pieces of sugar cane, and a compass is built by using one piece of redstone and 4 pieces of iron. Because you need a minimum of 9 maps to complete this, you will need 9 compasses and 56 pieces of paper.

It should noted, if you can't be bothered building all these maps, everytime a new player spawns into the world, they are given a free map, so you can just keep spawning in guests and having them place their maps in a chest to do this much faster.

You can start on this as soon as you have 1 map, but it will be easier if you just wait until all 9 are built. From there its really just a process of filling up each map fully.

Edit: I highly recommend you be on peaceful doing this, I can confirm that if you are on any difficulty and switch the difficulty on your world to peaceful achievements will not be affected. While on peaceful you do not lost food and there will be no unfriendly mobs.

Edit 2: I also suggest you turn off your HUD in settings. The UI elements will block parts off parts of the map, which can make it difficult to see areas of the map you have missed in these areas.

Filling up the maps

I would recommend the area you have a house set up in be the middle map, so take a single map out when you are by your base and press to open it up. Doing so will reveal a small circle of terrain around you (an arrow) as well as show any other players within the map as different colored arrows.

Walking in any direction will reveal more of the map, so needless to say, you need to fill up the entire map. Try and systematically move through the terrain, so as to not miss anything, go back and fourth. It is quite tedious to do this by just walking, as such I recommend you try and find a horse to ride (if you don't have one already, they will spawn in grassland biomes) as well as bringing a boat, allowing you to cross bodies of water much faster. Fill up this entire map and look carefully at it to make sure there is no bits you missed,

Once you finish the first map, you want to use it as a guide to see where to start the second one. Since this one is the center most map, you can go either up, down, left or right of this map to start the next one. You want to watch yourself on this map and as you approach the border of the map you will see you go from an arrow to a circle, this means you have entered the next map territory and can open a fresh one, beginning anew.

It is important you do not open up a new map in a territory already explored, as this will immediately fill up the whole map with whatever you had already explored in that area, so you have a duplicate map, and it can not be reset, which means you will need to build an entirely new one.

From here, the process is simple, just fill up all nine maps, it takes a very long time, but be deliberate so you do not miss any spots. Getting additional people in your game can speed things along quite a bit, everyone taking there own map and filling it up, make sure you coordinate well so you do not fill two maps with the same area.

Once all 9 maps have been built, you will require 9 item frames to put them. An item frame requires 8 sticks and a single piece of leather. Place all 9 in a 3x3 square on any wall and fill each item frame with the correct map (so the ones adjacent to each other in the world are also placed in adjacent item frames.

When they are all placed you get a really cool huge map made up of all the smaller maps, the player who places the final map gets the achievement, but if you just punch any map out and have another player place it they too will get the achievement.

If you place the final map and it doesn't unlock, make sure the maps are in the correct order, the terrain will line up if they are. If this doesn't work, chances are you misses some part of the terrain on one map, so study each one carefully. The color of unexplored map is very similar to sand, so make sure it is actually missing, and not just sand.

This achievement is very boring and takes a long time, but you get a nice 40 GS award for doing it, as well as an awesome map to put in your house. Good luck!

This achievement is super simple, yet super time consuming and just generally annoying to complete. You need to place 9 fully explored maps into a 3x3 item frame formation. I'd recommend setting your HUD opacity low and setting the difficulty to peaceful!
I also have a video guide available on the topic

This is just an add on to every other solution, but it makes this achievement take about 1/3 or 1/2 of the time it should take at least for me. If you play the tutorial world, there is an elytra in the chest near the two towers when you spawn. I also made myself a diamond axe with the diamond blocks in the beacon room or on the towers, whatever is easier for you. I mined enough wood to have 3 stacks of planks or 48 wood blocks. I built up until either the block limit or until I had enough blocks. Now once your up there, disable autosave and save the game. Put the elytra on and jump off with a map in your hand. I used the map to see where I was flying since there were no obstacles in the way. Once you land just repeat the process. During one flight, which takes less than a minute, I was able to fill out around 20 minutes of the map if I were just walking.

Edit: I haven't played this in a long time so I'm not sure if it will still work, but when I did this every time I started a new map / went out a loading distance the elytra in the main chest respawned.

Everyone out there, please look closely. This is just an add on to everyone else's ideas like using elytras, horses, boats, etc. But here comes my part of this idea. Once u start the tutorial edit the world then go to world options and change it to large world. This will make it so it's possible to get the achievement. But then. Gather All 9 unexplored maps, and grab your elytra, then find fireworks. Fireworks ROCKET propel you up into the sky when using an elytra

-DownwardCrown40

Not a solution just some tips

An Elytra is very handy
Use Peaceful difficulty
To check if you missed anything put your map in an item frame as bits not explored are brown not yellow (yellow is confused with deserts)
You might want to name your maps on an anvil to remember which is which (e.g Map North East)
Disable autosave and save frequently (so if you die you can exit without saving)