You definitely got me off to a good start; thanks!
I still have a lot of questions though. Since I wasn't sure exactly how to create a table of characters (I have no idea what "checking each character by index number" meant) I went ahead and tried converting the file to .html and reading it with Chrome. There was a ton of unreadable garbage in there, but plenty of English, too (and French and German. Go figure). Anyway, I'm assuming, since a lot of in-game text showed up in English, that I don't have to create a table file for it. BUT WAIT there's more.
When I change the game file to a .html file, it's still a huge file. So huge, in fact, that Chrome crashes before it can load all the text. I opened the .html file in WindHex and it handled it, but I still couldn't find any of the Scan Data, which I found very odd. I extracted all the root files I could find using Dolphin and started doing the same with those. There was even a Logbook.pak file that contains all the logbook entries. But I still can't find a file that contains all the Scan Data - or one that contains any Scan Data. Very frustrating. Anyone know what I'm doing wrong?
Glad I could help!
I'm not sure what to suggest about the Scan Data as I don't have the ISO and haven't played any Metroid games. It's possible that it could be in another encoding unlike the other readable text (though I don't see why the developers would need to do this), or if the Scan Data contains text that are graphics that could be why you can't find them.
Did the text in WindHex appear the same as it did in the right Chrome encoding? If not, you can try downloading Notepad++
(I believe it won't crash for large files) and go to the 'Encoding' option and choose the right encoding from there, although actually changing the encoding and scrolling down may cause some lag.
If the Scan Data still doesn't appear, it's probably due to one of the two aforementioned reasons. In the case that they are graphics, there is a program called ConsoleTool
that may be able to display them.
To elaborate about index numbers, each text character has a special code that defines it. I guess you could compare them to color codes, but pretty much every memory address (e.g. a stackable object on an items screen with 0A meaning you have ten of them) uses index numbers (see the ANSI hex section here
for an example). Making a table file is just a list in the format of '(hex Number)=(character)' each line but to find what text characters use what index numbers requires hacking knowledge and it can be difficult to find them, (I can only find them in older games where there's a name entry screen and a cheat searcher, etc.) so I'm not sure what to do if the Scan Data is in a non-standard encoding, though since you found English text in a standard encoding, all of the text that aren't graphics probably are in that encoding as well.
I'm sorry if this isn't much help. I hope you're able to find the Scan Data soon.