Goran Runfeldt, a fellow genetic genealogist, has developed a killer app. You’ve heard of “The Terminator?” Well, meet “The Triangulator.”
Goran developed the Family Finder Segment Triangulator tool to run, using a user script or browser extension, on the Family Tree DNA site, after you sign in to your personal page. So there is no downloading, no spreadsheets, nothing messy.
The Triangulator tool is still in beta, so while the documentation is rather sparse, the tool is extremely intuitive if you understand triangulation.
What is Triangulation?
If you don’t understand triangulation, what it is, how it differs from match groups, and why you would want to utilize triangulation, may I please suggest that you read the following articles before utilizing the tool.
Concepts – Why Genetic Genealogy and Triangulation?
Concepts – Match Groups and Triangulation
Triangulation for Autosomal DNA
In a nutshell, triangulation provides you with a tool to show that not only do person A and B match you, on the same segment, but that they also match each other.
This means that they are not matching you on the same segment number from opposite sides of your family, meaning one person matching you from your mother’s side, and one from your father’s side. If they match other, as well as you, that means that they both descend from the same side of your tree (assuming they are not both matching you identically by chance.)
Family Tree DNA shows you, utilizing the chromosome browser, that two people match you, and on the same segment, but they don’t (yet) inform you about triangulation, although they are working on a triangulation tool.
In the following example, we have 5 known relatives to Barbara, whose background chromosome is black. As you can see, there are three possible triangulation points where at least two of the people match Barbara.
Just to be sure, I downloaded these matches to a spreadsheet to illustrate that these matches are not trivial in size – meaning based on their size, they certainly should be legitimate matches.
All three matching areas on this chromosome (grey, gold and blue) are large enough to be considered substantial, and when compared to the charts created by Philip Gammon in the Match-Maker-Breaker article, we see that there is almost no likelihood that these are false matches, or matches by chance. In that article, when phasing matches to parents, we demonstrated that 97% of the matches of 12cM or more and/or SNP density of 2800 or more phase to one or the other parent, meaning they are legitimate matches. At 15cM, 100% of a child’s matches also match a parent, except for the X chromosome.
All of these cousins descend from Barbara’s paternal side, from the same family line, so the chances are pretty good that they do all triangulate, but let’s see.
Installing the Triangulator
First, you’ll need to install the triangulator.
My choice is to utilize the tool in Chrome, as I had difficulties with Internet Explorer compatibility. Chrome works just fine.
Goran has provided installation instructions for various browsers here.
If you’re installing this tool in Chrome, be sure to sign in to the Chrome web store while using Chrome to install the free app, or the store will ask you to download Chrome.
The installation is super easy – just one click, literally.
Ok, now the hardest part is over and we can get busy triangulating right away.
Sign in to your account at Family Tree DNA, using the browser where you just installed the tool.
Click on your Family Finder matches.
You’ll notice something new right away, a new icon that says “dnagen tools” at the top of your Family Finder matches. That’s the Triangulator.
On your match list, select the people you want to triangulate, just like you were selecting the people to compare in the chromosome browser.
Your comparison list will be built, like always, on the lower left hand side of your screen.
To triangulate, instead of clicking on the Chromosome Browser button, you’re going to click on the new dnagentools icon.
You’ll see a little dropdown box that says “Triangulator.”
Just click on “Triangulator.”
You’ll see the progress bar as the tool calculates the relationships of the people you are triangulating to each other.
When the tool finishes, it switches to the Triangulated Segment tab, which is what everyone wants to see first, but you can always click on the Relationships tab to view the various relationships of the people you selected to each other.
All of the genetically estimated relationship of all of the people you’ve triangulated to every other person in the group are displayed.
When the Triangulator is finished, you’ll see the “Triangulated Segments,” tab displayed, assuming some segments do triangulate, with a small image of the chromosome beneath each triangulated segment. The area where the segments match to you is colored in orange and where the segments all triangulate is colored in red.
Additionally, the tool shows you the actual overlap range, the number of matching positions and the overlapping number of SNPs as well.
If you think you’ve died and gone to triangulation heaven, you have.
In order for you to easily transfer this information to your spreadsheets where you are triangulating your segments (you are, aren’t you???) and assigning segments to ancestors, Goran has provided a nifty tool for that too.
At the bottom, Goran has included downloads of:
- All matching segments for these people
- The triangulated segments for these people over the match threshold selected, which defaults to 5, same as the chromosome browser
- The relationships of these people to each other
Yes, you can lower the threshold, but just remember that as you do, the chances of the segments being identical by chance increases.
The Answer to Our Problem – Triangulation is Critical
In case you’ve gotten all excited about triangulating and forgotten that we were in the middle of a story problem, let’s look at our answer.
If you recall, there were three candidate regions for triangulating between Barbara’s known cousins on chromosome 3.
However, the Triangulator only shows two triangulating segments, the first and third. That means that the second of these large segments does NOT triangulate. That means that one of these third cousins matches Barbara on that segment in one of these three ways:
- By chance
- Because the overlapping matching region is too small to be considered a match
- One person matches from Barbara’s mother’s side and one from her father’s side – as unlikely as that seems with third cousins.
The most likely reason for non-triangulation is the third reason, given those large matching segment segment sizes.
While the first and third (grey and blue) segment match groups both triangulate, the middle (gold) region does not.
If you’re shocked, just remember that no matter how intuitive a match seems, and no matter how “sure” you are that two people from the same line of your family certainly must triangulate because they both match you on the same segment, without triangulation, you REALLY DON’T KNOW!
And you all know about assume, right? Been there, done that, got educated!
Triangulate removes the assume from the equation.
In this case, triangulation tells me that I need to look on Barbara’s mother’s side for a second common ancestor with either C. Lentz or W. Lentz.
Just so you know, I was suspicious of this result, but given that I have access directly to the kits of both C. and W. Lentz, because I tested them both, I verified that they don’t match each other on this segment, both at Family Tree DNA and at GedMatch. So this is no mistake.
This triangulation tool is a “goodness of heart” free application shared with the genetic genealogy community, and while Goran is willing to share, he doesn’t really want his inbox to be swamped. In the tool, he provides the following support information.
Goran follows the ISOGG Facebook group, so posting questions there will provide answers for you, and maybe for someone else following along too.
What if I Haven’t Tested at Family Tree DNA?
The Triangulator tool requires chromosome segment data, thankfully provided by Family Tree DNA. Therefore, this tool is not available for use with Ancestry data at Ancestry. You can, however, download your Ancestry DNA file to Family Tree DNA. Not everyone who tests at each vendor uploads to other places, so be sure to fish in all of the ponds, one way or another.
You can read about which vendors’ files are compatible to transfer to Family Tree DNA (and other places too) in the article Autosomal DNA Transfers – Which Companies Accept Which Tests?
The following chart shows transfer Files Accepted at Family Tree DNA.
||Fully Compatible Version
||Partially Compatible Version
||V1 – until May 2016
||V2 – after May 2016 to present
||V3 – until Nov. 2013
||V4 – Nov. 2013 – Aug. 2017
||V5 – Aug. 2017 to present
Keep in mind that the current V5 version of the 23andMe test is not compatible at all at Family Tree DNA. The 23andMe V4 version, in use between November of 2013 and August of 2017 is only partially compatible, as is the Ancestry V2 version in use since May 2016.
If you upload partially compatible versions, you’ll receive your closest (meaning largest) matches, generally about 20-25 % of your matches that you would receive if you tested on the Family Tree DNA platform. However, you’ll be missing most of your matches, and you never know where that match you desperately need is hiding.
Note that this isn’t an artificial restriction imposed by Family Tree DNA, it’s a function of the other vendor’s chips only being partially compatible with the DNA processing chip used by Family Tree DNA.
If you want to see all of your matches and all of your segments, purchase the Family Finder test at Family Tree DNA.
A really big thank you to Goran and the user interface developer, Jonas, for this wonderful tool.
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