Friday, May 19, 2017

Gedmatch Segment Triangulation Bar Chart

This is pretty simple.
Across the top of your chart you have header

You can see all the contact information for those in your possible triangulated groups.

I recommend you add one column to your spreadsheet so you can enter the name of the common ancestor you share with your match.

The segment bar chart (as the tree graphic) include only a portion of the people you match. (This is a Beta tool.)

Pretend you are looking at a ruler with a segment laying on top. This ruler is divided into centemorgans (cM). The "from" and "to"  is the position where you and your matches measurement starts and ends.
To get a better idea you can reduce the view size of your page.
 Fig. 1

Every Match with overlapping segments in a TG will have a Common Ancestor – an ancestor who passed the DNA segment to each of them. Which ancestor you all share is determined by genealogy.-Jim Bartlett

The gray areas indicate a break where a new chromosome begins.

Where you see well aligned bars indicates common ancestors. 

If you are new to triangulation, you should focus on those matches who share a 15 cM size or larger.
You often share different segments on different chromosomes with matches as you "climb" your trees. Each shared segment will represent a different common ancestor or set of grandparents. 

Contact those who overlap and share trees. Collaborate if you see who they need to add to connect with you.

When combining triangulation with a specific surname project, triangulation becomes a process of elimination. You confirm other branches of your tree as you search for those in your surname project. It is beneficial for everyone within the surname project to compare their Gedmatch Kit numbers to see where (if at all) they relate to others in the project. Not all cousins will match each other. Some will.

An example might be if you share atDNA with a cousin who descends from a common couple.

As an example I will use my fifth great-grandparents,  Hugh and Hannah (McCormick) Brady.

One match may descend from their daughter Mary and another may descend through Samuel, another through Ebenezer. Your most common ancestors with whom you share DNA is going to be Hugh or Hannah. Three cousins from different children's lines who match on the same place on the same chromosome confirm Hugh and Hannah as your common grandparents using atDNA. 

Now, do a surname search at your testing company, in this case search for McCormick. Can you find a McCormick who matches you and a known Brady cousin on this or another segment? This will help you figure out what piece of a chromosome is from Hugh and which part is from Hannah.

Begin sending emails to those people whose segments overlap yours and find out who your common matches are.

Happy Finding!


  1. Thanks to your excellent description about Segment Matching, I renewed my subscription to Tier I. Now I can understand what I am looking at ! It's also good that you mentioned " they hold the potential to be a triangulated group." Very important.

    1. Thanks. So glad people are reading this blog. Sorry for the delay in responding, I get so busy having fun I forget to click in all the places I am supposed to in my email.