Truncated Huffman tree for the compression of the LFI 30 GHz channel at N_side = 512 on PID 27 646. The ovals represent the “leafs” of the tree, each of which contains a single number to be compressed. To determine the symbol that represents each number in the Huffman binary array, simply read down the tree from the top, adding a 0 for every left branch and a 1 for every right branch. The number −2, for example, is in this table represented by the binary code 11010. Dotted lines represent branches that were truncated for visual reasons. The full tree contains 670 unique numbers with a total array size of 861 276 entries.