For me, the Shared Segment Spreadsheet is a critical tool, which evolves through four incarnations.

1. It starts as a collection of all your shared DNA segments – from each company. This also means a collection of all your Matches (except AncestryDNA), some with multiple shared segments. It can be searched and sorted.

2. Use as a segment Triangulation tool. Sort on: Company + Chromosome + Segment Start to arrange all the shared segments (within a company) into Chromosomes. And within a Chromosome they are arranged so that overlapping segments are close to each other.  With this “view” each segment is Triangulated with other overlapping segments, or not. Maternal and Paternal Triangulated groups are formed*. Some of the under-15cM segments will not Triangulate and are labeled “false” and deleted or moved out of this spreadsheet –  “everybody’s got to be somewhere.”  This process is repeated for each company.

3. Form/identify Triangulated Group (TG) segments. Sort on: Side + Chromosome + Segment Start to separate the maternal and paternal segments and sort them in order within each chromosome. Since this spreadsheet is comparing all these shared segments with your own DNA segments, the shared segments from different companies will “break” into TG segments that align with your own segments. However, this phase of the process requires some judgment – the data is a little fuzzy and the ends of TGs will not be precise. You have to make a call. In general, to align with your DNA segments, each TG will end at the same Mbp as the next one starts. Make those calls and assign a TG Identification (TG ID)** for each segment. Make a TG segment header row for each one (I have 372 TG segments) that lock in the overall TG start and end positions and TG ID. TIP: make the TG header start location 0.01Mbp less than the first shared segment in the TG – so it sorts on top of the individual segments. Remember that every Match in a TG is related to you on your line back to a specific Common Ancestor (CA). Note: some small segments in a TG may go back further.

4. Use these TG groups to do the genealogy! Among the Matches, find the consensus path to the CA.

Summary: A shared segment spreadsheet has several uses – collection > Triangulation > TG ID > genealogy. The TG segment is your DNA segment. This covers all of your genetic genealogy, but you can always focus on one or more individual TGs, if you don’t want to eat the whole elephant at one time.

*I’ve covered the Triangulation process in other blogposts, and won’t repeat that here – this blogpost is about the three incarnations of the spreadsheet.

**I’ve covered TG IDs in other blogposts

[35BBa] Segment-ology: Shared Segment Spreadsheet Incarnations by Jim Bartlett 20251102