A method for longitudinal position (LPOS) detection in a magnetic tape storage system for storing data upon linear tape open (LTO) magnetic storage tape, which data includes odd and even 36-bit LPOS words with error correcting ability. The method includes first encoding positional information onto the tape within the 36-bit LPOS words using each LPOS word's 8-bit sync mark field, and six of each LPOS word's 4-bit symbol fields, wherein 6 of 24 total bits comprise the encoded 8-bit sync mark field: Sy, and six 4-bit symbol fields are utilized as parity bits. The magnetic tape storage system passes the LTO magnetic storage tape encoded with the odd and even LPOS words with error correcting ability longitudinally across a servo reader/writer at a known speed, decoding the encoded positional information and detecting and correcting both ambiguous bits and single erroneous bit errors.