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Louis Kessler's Behold Blog

My #RootsTech 2017 Schedule - Sun, 29 Jan 2017

I finalized my schedule for RootsTech about a week ago (have you finalized yours yet?) of what I plan to do. I’ve put it on my online RootsTech App as well as on OneNote on my Phone in case the wifi at the Conference is spotty.

If you want to track me down, this is where I’ll be:

Monday, Feb 6

My Flight Arrives
7:45PM to 7:55PM

Commonweath Dinner Meetup
8:30PM to 9:00PM
Blue Lemon

Tuesday, Feb 7

BYU Family History Technology Workshop
7:30AM to 5:00PM
Brigham Young University

Media Dinner
6:30PM to 8:30PM
Room 355

Innovator Showdown Semi-Finalist Technical Setup
8:35PM to 8:45PM
Ballroom B

Wednesday, Feb 8

Innovator Showdown Semi-Finalist Rehersal
7:00AM to 8:00AM
Ballroom B

IS7000 Innovator Summit General Session
9:00AM to 10:00AM
Ballroom B

IS7100 Industry Trends and Outlook
10:15AM to 11:15AM
Ballroom B

IS7303 Innovation: Best Practices and Applications
11:45AM to 12:15PM
Ballroom J

IS7200 Innovator Showdown Semi-Final
12:30PM to 1:30PM
Ballroom B

IS7702 How to Pitch an Investor
2:00PM to 2:50PM
Ballroom J

RT8642 How will DNA continue to disrupt our industry
3:00PM to 4:00PM
155A - Getting Started

IS1743 FamilySearch API: What’s New and What’s Coming?
4:30PM to 5:30PM
Ballroom G

RT1006 Welcome Party: We Don’t Need Roads
6:00PM to 7:30PM
Marriott Downtown

Thursday, Feb 9

RT5100 General Session - Thursday
8:30AM to 10:00AM
Hall D

LUN9001 MyHeritage Sponsored Lunch
12:00PM to 1:30PM

RT4117 It’s a Collaborative Work: Blending FamilySearch and Partner Applications
3:00PM to 4:00PM

LAB2064 Your Health. Your Legacy. Their Future.
4:30PM to 5:30PM
251B - LAB

RT1054 RootsTech Opening Event: Music It Runs in the Family
8:00PM to 9:30PM
Conference Center

Friday, Feb 10

RT1200 General Session - Friday
8:30AM to 10:00AM
Hall D

IS2543 Innovator Showdown Final
10:30AM to 11:30AM
Hall D

LAB1616 Introduction to Chromosome Mapping
3:00PM to 4:00PM
251E - LAB

RT1876 Culture Celebration: Celebrate Your Heritage
5:30PM to 7:30PM
Expo Hall

MyHeritage RootsTech After-Party
8:00PM to 11:00PM
Mariott City Creek

Saturday, Feb 11

RT1300 General Session - Saturday
8:30AM to 10:00AM
Hall D

Flight Home
3:20PM to 8:20PM

During my unscheduled time, I’ll likely be roaming around the Expo Hall. I’ll also make sure I get a chance to go to the Family History Library and see their new Discovery Center.

It does look like time to eat and sleep will be in short supply.

Track me down if you can, and I’ll give you a couple of ribbons:

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Triangulation, Single Matching and Double Matching - Fri, 27 Jan 2017

It seems like my last post was a bit confusing to many people. I expect that the way I drew the boxes (to be segments) and the way I connected them with lines (indicating matching) was not intuitive, and it did not allow people to see that Double Matching with two people actually triangulates.

I’m going to start from scratch here. I’m going to use an illustration that hopefully most people will understand. This will be a representation of FamilyTreeDNA’s  Chromosome Browser which most people reading this should be familiar with.



Below is a representation of the Chromosome Browser as seen by three different people when they log in to their account at FamilyTreeDNA. Person a will see the top diagram, Person b will see the middle diagram, and Person c will see the bottom diagram. One person cannot see the diagrams of the others.


In the top diagram, Person a’s Chromosome Browser shows a match with Person b and Person c on the same segment.

If you log into Person b’s results, their Chromosome Browser will show a match with Person a and Person c over the same segment.

And Person c’s will see that their Chromosome Browser says Person a and Person b match on the same segment.

This is called Triangulation, where three people all match each other on the same segment. Person a matches Person c, Person b matches Person c, and Person a matches Person b.

The purpose of Triangulation is to help you identify segments that may be Identical by Descent (IBD) because those that are IBD come from a common ancestor of the people who share the same segment. Then through genealogical research, you trace back each of the people’s trees to see where they connect.

For a segment to be IBD, it must Triangulate.

However, a segment that Triangulates is not necessarily IBD. There are a couple of reasons for this:

  1. Two segments may match by chance. This starts happening when segments are shorter than 15 cM and happens more often as the segments get smaller.
  2. Two segments may be on opposite chromosomes. This situation was identified by Blaine Bettinger a couple of days ago on the International Society of Genetic Genealogy (ISOGG) Facebook page. In other words, one segment is the maternal segment and the other is the paternal segment of a chromosome pair.


Single Match Triangulation

This is the method most people use for Triangulation. It uses one person’s matches:


What you have shown so far by this is that Person a matches Person b, and Person a matches Person c on the same segment. You have not yet Triangulated because you must also show that Person b matches Person c on the same segment. The above Chromosome Browser image does not tell you that. And Person a does not have access to that Person b match with Person c in their own match information at FamilyTreeDNA or at 23andMe.

What Person a can find out from their own account at FamilyTreeDNA or 23 and Me is if Person b is “In Common With (ICW)” Person c. That means Person b shares enough DNA with Person c to be considered a match. If that is the case, then it increases the likelihood that the segments Triangulate, but it does not guarantee it because those matches between Person b and Person c may not be on the same segment. There are several tools that make use of ICW data to help you locate Triangulated segments, such as Don Worth’s Autosomal DNA Segment Analyzer (ADSA) at DNAGedcom.

However, to truly Triangulate, you need to verify that the Person b and Person c segments match each other. The one obvious way to do this is to contact either Person b or Person c and ask them to look in their Chromosome Browser to see if they match the other person over this specific segment. If they do, you have verified that this segment Triangulates between Persons a, b and c, and the segment therefore might be IBD.

If Person b or Person c tell you that they don’t match the other person over this specific segment, then they have verified that Persons a, b and c do not Triangulate over this segment and have shown that the segment cannot be IBD for the three of them.

This is however a lot of work, to verify every segment with every person on a one by one basis if you do it manually.

There is just one tool out there that will check the third match for you. It is the GEDmatch Tier 1 Triangulation Tool. It actually looks at the segments of Person b and Person c to ensure that the same segment matches with Person a. GEDmatch find all the pairs of people who match Person a. So it will display all the Triangulations it finds, whether paternal or maternal and does not differentiate.


Double Match Triangulation

This method makes use of two people’s match information. When each they log in to FamilyTreeDNA and look at their Chromosome Browser, Person a will see the top diagram, and Person b will see the bottom diagram.


Using just two people’s information, you can truly Triangulate. This is why:

Person a knows of their segment match with Person b, and knows of their segment match with Person c, but does not know if Person b matches Person c on the same segment.

Person b knows of their segment match with Person a, and knows of their segment match with Person c, but does not know if Person a matches Person c on the same segment.

If you put that data together, then you know from Person a that Person a matches Person c on the segment, you know from Person b that Person b matches Person c on the segment, and you know from both of them that Person a matches Person b on the segment. You have the three matches on the same segment that you need for true Triangulation.

So only data from two people is required to Triangulate. You do not need the data from the third person.

When Person a downloads a Chromosome Browser Results (CBR) file from FamilyTreeDNA, it contains all of Person a’s segment matches with everyone else. When Person b downloads their CBR file, it contains all Person b’s segment matches with everyone else. Using these two files, you can therefore find in one fell swoop every segment that is a true Triangulation that involves Person a and Person b and someone else.

This is the method that Double Match Triangulator uses to Triangulate. The method of Double Matching ensures that Person a matches Person c, Person b matches Person c, and Person a matches Person c all on the same segment, which is exactly what the GEDmatch Tier 1 Triangulation Tool does as far as Triangulation goes.

But DMT takes this one step further because of its Double Matching. Only segments that Double Match both Person a and Person b will be included in the Triangulations for those two people. So the triangulations are effectively filtered by the relationship of Person a with Person b. For example, If Person b is a 2nd cousin of Person a, then DMT will produce Triangulations with only people that are not only related to both Person a and the 2nd cousin, but also need to have segment matches between Person a and the 2nd cousin that yield true Triangulations. By comparison, GEDmatch does not differentiate its Triangulations and thus does not give you the ability to filter them.

But always keep in mind that even though both DMT and the GEDmatch Triangulation tool both produce true Triangulations, a true Triangulation does not guarantee that the segment is IBD (see above for the two reasons). Determining IBD is a separate issue that neither DMT nor GEDmatch can yet address.

Comparing Single Matching to Double Matching - Wed, 25 Jan 2017

Important Note:  After this article was written, I found many people had trouble understanding the concepts, as the diagrams were confusing them more than helping them.

This article has been completely rewritten (just two days later) and uses a different diagramming that is akin to looking at the matches in a Chromosome Browser. It should not only be much more easy to understand, but it adds comparisons with the ADSA and GEDMatch Triangulation tools.

I’m leaving this article here as another method of explaining the same thing, but if you haven’t read the other article yet, I’d recommend you read it first:
Triangulation, Single Matching and Double Matching


Let’s see if we can define everything in an understandable way.


Single Matching

For Person a, find all the Persons c, d, e, … who match or overlap on the same DNA segment.

This is what FamilyTreeDNA and 23andMe give you today. MyHeritage is promising a Chromosome Browser but no word yet on whether you’ll be able to download segment matches. AncestryDNA does not provide you with your segment match data.


The goal here is to find the people who get that DNA segment from the same common ancestor, Identical by Descent (IBD), as that will prove a relationship. But this must be checked thoroughly, because one of each pair of chromosomes comes from the mother and one from the father, and the DNA company’s matching process cannot distinguish one from another. So any match, one that even criss-crosses between the mother’s and father’s chromosome will count, as will random matches by chance. With small segments below 15 cM in size, there is a significant likelihood of there being a false match that is not IBD. Even above 15 cM, the segments may still be to the different parent. The main technique to help you identify if the segment is IBD is Triangulation (see below).


Double Matching

For Person a and For Person b, find all the Persons c, d, e,… who match both Person a and Person b on the same segment.

This is what my Double Match Triangulator Program will give you today. And this is what you want FamilyTreeDNA, 23andMe, AncestryDNA and MyHeritage to be giving you.


Double matching does a lot for you. It uses a second person to help confirm that Person c, Person d and Person e all match each other and are not just matches by chance. It eliminates the extra bits of random match that Person a and Person b may have with the third person. If Person a and Person b are not direct-line related (i.e. parent-child, grandparent-grandchild), then it will reduce the threshold of where false matches will occur, down to maybe even 5 cM as Jim Bartlett has concluded. I plan to do a study of this soon and will put my results in an upcoming blog post.



Triangulation is a technique to help conclude (I won’t say “prove”) that three people share a segment that comes from a common ancestor and that the segment is Identical by Descent.

It requires that Person a match Person c on a segment, Person a matches Person d on the same segment and also that Person c matches Person d on the same segment.


This statistically reduces to almost zero the possibility of the criss-crossing matches between the two parental chromosomes. It is still possible that one of the 3 people matches by chance to the other two people. But should that chance match be disproved, maybe by multiple Triangulations with other people, then it can be concluded that these people obtained that common segment from a common ancestor.


Single Match Triangulation

This is the technique commonly in use today because you are only supplied with Single Match information by FamilyTreeDNA and 23andMe.

That matches between Persons c, d and e are not included in the Single Match data you get. You don’t have this information in your matches. What you need to do is contact either Person c, d or e and ask them to look in the Chromosome browser and see for you if they match the other people on that particular segment. If they do, then you Triangulate on that segment. If they don’t match to some of the others, then you’ll have to contact the others to get them to check.


You could have tens of thousands of segments that SIngle Match with others. You may have dozens of people who overlap on a segment. So to be practical, most people just concentrate on their largest size segments, or on a segment connected to people they are trying to figure out their relation to. This is manual labour as far as I’m concerned. And it only verifies one segment for a few people. You have all your others you can do as well that have so much info to give you.

So what people often do is they get lazy. Maybe they verify with one or two people and then incorrectly conclude that all the other matches on the segment are valid. Then maybe they just look to see if the other people are “In Common With” meaning they match somewhere, but not necessarily on the desired segment, and then conclude the segment Triangulates, which is not a conclusion you can make.

Single Match Triangulation is what Jim Bartlett has done over the past five years. He has done it correctly and meticulously. By mapping his segments to his matches, he has manually Match Filtered (I’ll explain what that is in a future blog post) to his parents and has been able to map most of his segments to his ancestors. But it took him 5 years! It’s not easy.

There is one tool that does true Triangulation for you. It is the GEDMatch Tier 1 Triangulation Tool. It is the only online tool that will properly check the third leg of the triangulation for you and guarantee that it is a true Triangulation. All the other tools out there use “In Common With” or less. However, with GEDMatch, you are limited to the kits that have been uploaded there, only your closest 500 matches are used, the minimum cM match is 7 cM and 500 SNPs and it gets cut off at 10,000 Triangulations.


Double Match Triangulation

This is the technique I implemented in my Double Match Triangulator (DMT) program that uses Double Matching.

The basis is simple. Once you’ve Double Matched Person a and Person b with other people on a segment, you have all the matches you need except one: the Person a with Person b match. And that you’ve got that right in your own Single Match file.


The matches between Person a and Person b could then be compared to all the Double Matches, and those that overlap all Triangulate, and those that don’t are Missing a-b Segments (another word I invented).

With the Chromosome Browser Results (CBR) files of Person a and any Person b that is Person a’s match, you can find every segment that Triangulates and all the people that Triangulate with them on every segment in one fell swoop.

If you can get CBR files from more of your DNA matches and put them all together, you will be doing what I call EAST (Extreme Autosomal Segment Triangulation).


Hopefully this post makes the concepts all a bit clearer for you.