Where are the important offsets in the ROM file?

I mean file offsets for the ROM file, not the memory location when the ROM is loaded in the SNES. For example, what is the offset to the overworld map layout? I assume that the overworld map is a byte array, and that each byte points to a graphics tile in the graphics tile set. Each tile is 16x16 pixels in size, and the overworld map itself is 256 tiles wide and 256 tiles high. And there's 2 dimensions, plus one set of special areas, for a total of 3 such tile index array. So the overworld map takes 65536 bytes for each tile index array, for a total of 196608 bytes in the ROM, and each byte is an index to a tile in the graphics tile set. But are these 3 arrays of bytes/indices? What are the offsets they are at in an unmodified ROM file? Also what is the offset to the tile set? Of course each pixel in a single tile is itself an index to a color in the game's color palette, so I also will need to know where the game's palette is stored. Once I figure these things out, I hope to be able to render the entire map, into a single image file for viewing on a computer.