The methods and apparatus 100 disclosed herein concern DNA sequencing. In some embodiments of the invention, the methods comprise measuring the distance between labeled nucleotides 220, such as nucleotides labeled with bulky groups. The methods may further comprise placing identical template DNA 200 into four reaction chambers 110, 120, 130, 140, each containing a different labeled nucleotide precursor, synthesizing complementary strands 230, 240, 250 and detecting labeled nucleotides 220. The distances between labeled nucleotides 220 may be used to construct 450 distance maps 310, 320, 330, 340 for each type of labeled nucleotide 220. The distance maps 310, 320, 330, 340 may be aligned 520 to obtain a nucleic acid sequence 210. Overlapping data analysis and frequency analysis may be used to construct 450 the distance maps 310, 320, 330, 340 and non-overlapping data analysis may be used to align 520 the distance maps into a sequence 210.