Illustration of the construction of composite segments. Each line represents the chromosome sequence of an individual. The colored circle represents the consecutive sequence of a segment size 0.02 cM, which may contain multiple SNPs. A composite segment of size 0.2 cM is composed of 10 consecutive segments of size 0.02 cM from 10 different individuals. To create a composite segment of size 0.4 cM, two composite segments of size 0.2 cM are constructed and merged. A similar procedure is conducted to create composite segments of size 0.6, 1 and 2 cM, where three, five and ten small composite segments are constructed and merged respectively.