Double Match Triangulator (DMT)

Double Match Triangulator is a currently free autosomal DNA analysis tool.
It combines two or more different people's Chromosome Browser Results (CBR) files from FamilyTreeDNA
to provide Double Match and Triangulation data that can be used to help determine genealogical relationships.

DMT placed 3rd in the RootsTech 2017 Innovator Showdown

On March 10, 2017, DMT will move to its own website at:
On that date, it will become commercial software you will have to purchase a license for.


This version of Double Match Triangulator is freeware.
It runs on Windows 7, 8 or 10.
If you have Office 2007 or later, it produces an Excel file, otherwise it creates a .csv file.
Current release: 1.4.1, 16 Feb 2017

Click here to Download*
* Double Match Triangulator contains no adware, spyware, viruses or malicious software of any type.

Certification by Comodo Security Services For your safety, the download files are digitally signed. This will verify that it is my program
and guarantee that the code has not been altered or corrupted since I created and signed it.

If you don't have CBR files of your own to use,
Try this set of 5 sample files used in the Help file

They are compressed in zip format


About DMT

Important: Double Match Triangulator is not a program for newcomers to genealogy or even to newcomers to genetic genealogy. It does require experience analyzing DNA segments because that is that task which the program is innovating upon. The people I expect to use DMT are advanced genetic genealogists who have gone as far as they can go and need another tool to take them further.

DMT is an autosomal tool that allows the genetic genealogist to look at their autosomal data in a slightly different way than other methods. It assists by finding every segment from every matching person that double matches and additionally those segments that triangulate with two specific people, and produces an Excel file that contains a Map page containing all the matching segments and a People page listing all the people who match.


  • "Double Match" is where "a matches c" and "b matches c" on a segment. Only if "a also matches b" on the segment is it a "full triangulation", otherwise it is a "missing a-b" double match.
  • "full" is used with the term triangulation to distinguish it from the "triangulation" that many people incorrectly use to mean "a matches b" and "a matches c" on a segment and "c is in the in-common-with (ICW) list of a and b".

I cannot possibly explain everything about matching segments and triangulation. To learn about this, please read every post in Jim Bartlett's fantastic website.

The DMT Map page looks like this:

Double Match Triangulator delimits Double Match Groups (DMG) helping you identify segments of Person a's DNA that may come from a particular ancestor.

There’s more work for me to do on DMT. It is only displaying matches and Double Match groups right now. I feel it should be able to interpret your matches and define your ancestral segments and place where your tested relatives belong with respect to your ancestors. If I could do that, it would be a fantastic innovation, and then the program would be able to be produce the information wanted by everyone and could be used by anyone, including people new to DNA analysis.

If you use this program and develop some analytical analysis techniques using it that can be programmed, please contact me, and I may be able to add your methods into DMT for everyone to use.



This program requires Windows and has been tested back to Windows 7. If you have at least version 2007 of Excel installed on your computer, it will produce formatted Excel files in .xlsx format. If you don't have at least version 2007 of Excel installed, it will produce Comma Delimited files (csv files) which contain the same data and can be loaded into any spreadsheet program, but you won't get the nice formatting. In that case, you can format it yourself (e.g. cells with X = green, a = pink, b = blue, etc.)

Mac Users: Sorry, but I'm a Windows developer. If you have Excel on your Mac, you can still read in the files DMT produces. So ask one of your DNA relatives if they would run the program and send you the Excel output file. Also, Peter Sjölund said on Facebook that DMT "runs like a charm on a Mac using Crossover or some other software that lets you run Windows applications."


Using the Program

I've included a fairly comprehensive help file with the program. Please read it. Press the Help button in the program to open the help file. The last page of the Help File is about interpreting results.

Downloading from FamilyTreeDNA

DMT is designed to work with FamilyTreeDNA Chromosome Browser Results files. This file is a hidden gem at FamilyTreeDNA that not too many people have discovered. It contains all the segment matches with every person that is matched. This file can be very large, containing hundreds of thousands of lines and be 15 MB in size or larger.

Make sure you download the correct file. You do it from the Chromosome Browser page at FamilyTreeDNA by pressing the right-most link that says "Download All Matches to Excel (CSV Format)". The link you want to press is shown below in orange with the hand pointing to it.

Because the Chromosome Browser Results file is so large, it may take up to a couple of minutes after you click the download link before the FamilyTreeDNA site does anything at all, but then it will start to download the file. Wait until it says 100% before you try to use it. So be patient! Give it time to complete the download. Several minutes. Don't click the link a hundred times either.

Also, FamilyTreeDNA is a very busy site. Sometimes the download fails. If it creates a file whose name ends with _aspx, then it failed. Press cancel and try again or wait until later when their servers are less busy. The file created must be named: nnnnnn_Chromosome_Browser_Results_yyyymmdd.csv

And don't forget: You need two files. Yourself and someone else you are administering. If you don't administer anyone else, you'll have to ask a DNA relative to download theirs and send it to you.

Downloading from GEDmatch

The GEDmatch site does not provide a segment match download, but with a small bit of work, you can screen capture match information from GEDmatch and use it in DMT. See: Getting DMT to work with GEDmatch segment matches. Match files from GEDmatch cannot be used with match files from FamilyTreeDNA because the identifying people names are different. A similar process will also work for 23andMe match downloads. AncestryDNA does not provide match downloads.

Downloading from 23andMe

23andMe does allow downloading of chromosome matches. The next version of DMT will include capability to read these files directly. Until then, if you reformat them like a FamilyTreeDNA CBR file, then DMT will read them.

Downloading from AncestryDNA or MyHeritage DNA

AncestryDNA does not let you download your segment matches. The only way to get them is to load them into GEDmatch.

MyHeritage is a new service that does not yet offer downloads and GEDmatch does not have an upload for them yet. They do state that they will be adding data downloads in the future.

Keep In Mind...

You can't mix data between FamilyTreeDNA, GEDmatch and 23andMe. They do not all use the same builds (i.e. different base addresses), limit the matches that they give you in different ways, and don't use the same people names or kit numbers.

Small Segments: Triangulation does NOT guarantee that a match is Identical by Descent (IBD). It still could be a match by chance. I discussed this with Debbie Kennett and realized she is quite correct on this point. If person a and b are IBD, then if person c matches a by chance, then person c will also match person b by chance. However, triangulation is useful as it does reduce the likelihood of a chance match. Jim Bartlett is fairly confident that triangulation works down to 5 cM and my observations seem to confirm his.

But don't throw away the small triangulated segments under 5 cM: They may be by chance, but then again they may not. Finding multiple matches at certain crossover points will add weight to indicate which small segments may be real.

Also, don't throw the missing a-b double matches away. They can be very valuable and may come from a common ancestor who passed his segment to Person a and Person c, and the ancestor's spouse who passed her segment to Person b and Person c, which could explain why Person a and Person b don't match. Until the DMT program was made available, there hadn't been an easy way to identify missing a-b double matches, so no one so far has studied this and evaluated their usefulness. More research is needed to see how missing a-b matches can be used. See my blog post: Triangulation and Missing a-b Segments.

The key to analysis may prove to be looking at the crossover points. If multiple people have identical crossover points, it should reduce the likelihood of it being a by chance segment. Those crossover addresses given by FamilyTreeDNA seem to be quite accurate and seem to be consistent in different people's match files. And here as well, more research is needed to explore these possibilities.


Version History

Version 1.4.1, 16 Feb 2017 - Now checks that at least Excel 2007 is installed and if not, only produces .csv file. Fix to prevent crash that sometimes happened during By Chromosome runs when there are only a few double matches on a chromosome.

Version 1.4, 20 Jan 2017 - Now works if either File a or b was downloaded before the other person's results came in. Prevents the same person from being used twice. Excludes non-matches from By Chromosome analysis. Better handling of duplicate segments in CBR files. Improvements to People page. Several minor fixes and improvements. Updated help file.

Version 1.3, 12 Dec 2016 - Improved output on People page including some color coding to ease interpretation. Implemented the idea of Theorem 1 so Triangulation Groups are now determined independently of Double Match Groups. Updated help file.

Version 1.2, 21 Nov 2016 - Now can work if only Person a has b matches or Person b has a matches, which might occur if one file was downloaded before the other's test results were in. Excludes duplicate or overlapping segments in CBR files and prefixes such people with ##. The People page and file now include just the Person c matches with Person a.

Version 1.1.99, 18 Oct 2016 - Identifies Double Match Groups. Allows combination of multiple runs by Chromosome. Improved People Page/File.

Version 1.1, 27 Aug 2016 - Cursor now changes when running. Does not try to create Excel files on computers without Excel (so it won't hang) and creates csv files instead. Eliminated folders for Person a.

Version 1.0.1, 20 Aug 2016 - Fixed possible freezing on some computers when running.

Version 1.0, 18 Aug 2016 - Initial Release.

Version 0.99.1, 04 Aug 2016 - Private Beta.

Version 0.99, 03 Aug 2016 - Private Beta.


Out and Around



I would like to thank Sandy Aaronson, who put a lot of effort into testing the program while I was developing it, and first presented results from the program at the August 2016 IAJGS conference in Seattle, Washington.

I would like to thank my 3rd cousin Joel Koenig, and DNA cousins Arnold Chamove, George Gutman, Seth Brown, Bruce Levine, Barbara Hershey, Mark Horn and Sandy Aaronson, for sending me their Chromosome Browser Results files to test DMT with (and hopefully use DMT with them to find out "how" we're related).

I would like to thank Meir Gover for challenging me to use my tool to find an autosomal relationship before he would send me his Chromosome Browser Results file.

I would like to thank Debbie Kennett, who helped me to understand the pitfalls of using small segments under 7 cM, IBD, IBS and IBC.

And I would like to thank Judy Russell who implored me to get my 93 year old uncle's DNA tested immediately and so I did and it led to all this.