Recently, I was called out for abandoning Segment Triangulation.  Let me set the record straight. I like, and use, both Clustering and Triangulation – virtually every day! Each one has some unique strengths and some drawbacks. A (very) short review….

Triangulation. When I started Segmentology, in 2015, I was the Johnny Appleseed of Segment Triangulation. I don’t claim to have invented it, but I was definitely a fan, and, I think, took it to new levels. It has been called the “Gold Standard” in genetic genealogy. Your DNA is composed of specific DNA segments from specific Ancestors – Triangulation helps you to determine these segments, group your Matches by shared segments (and therefore ancestral lines), and develop (or “paint”) a Chromosome Map of segments. However, the critical step of determining the ancestral line is often hard (at least for me) because the companies providing segment data, in general, don’t have any/many good Trees.

Clustering. In late 2018, auto-Clustering was introduced, and we could easily get many Clusters depending on the range of cMs we used. With this tool, you could determine these families of cousins, group your Matches by shared Matches, and try to determine the Common Ancestor. This was a tool we could use with AncestryDNA (either auto- or manual Clustering), where there tended to be many more Trees and genealogy tools. It worked for me… However, at AncestryDNA we cannot get the segment data to tie Matches to DNA segments.

By 2020 I had finished my Triangulation and had 372 Triangulated Group (TG) Segments. I was growing frustrated because I wasn’t getting very far finding Common Ancestors. On the other hand, I was finding a lot of Clusters with pretty solid Common Ancestors. So, I shifted my focus and have mainly been using Clusters, ever since. I still look for close Matches with larger segments for Triangulation. But my focus is on confirming more distant Ancestors and working on Brick Walls – mostly with Shared Match Clustering.

Bottom Lines:

1. Comprehensive Triangulation is a lot of hard work; but it can be a good tool for specific segments that appear to come from/through a Brick Wall.

2. Clustering is somewhat easier and focuses more directly on the genealogy. I think it’s more fun; and a better tool for many hobby genealogists. A spreadsheet is not required (but it is helpful to track everything).

3. Again: I use both, every day!

[22DL] Segment-ology: Clustering vs Triangulation; by Jim Bartlett 20260407