Oh boy! The last few days when I’ve had a chance, I’ve been working in Gedmatch and figuring out how to triangulate my DNA+Gedcom matches. After finding several articles on Google – notably from Roberta Estes of DNAeXplained (Triangulation for Autosomal DNA) and a few others, I figured out my own system.
I am attempting to figure out which chromosome each of the matches correspond as well as how many of my other matches on the same chromosome match each other. Then I go in to each gedcom to look for shared ancestors.
Here is my step by step guide – just in case this system might be something you would like to try.
- Upload your raw DNA from Ancestry, 23andMe, Family Tree, or any of the others, to Gedmatch.com. Make sure your raw data is in a .zip file. (Gedmatch is FREE!!)
- After doing that, upload your gedcom file preferably with BOTH maternal and paternal pedigree lines. (My personal note: There have been so many matches I’ve found where one or the other side is not part of the gedcom – kind of hard to figure out a match if you don’t put the whole thing up there!)
- On the Gedmatch home screen, you will want to click on Gedcom+DNA matches.
- On the next screen you will input your DNA Kit number (which you will receive upon uploading your raw DNA data).
- The results page will show a spreadsheet type of chart that will include the following information for your matches: the DNA kit number, the different types of shared & etc. cMs (centimorgans – DNA language!), the Gedcom ID, DNA name, Gedcom name, and an email address of your match. Do NOT start emailing your matches or use the emails in a batch file. Abuse of emails is not what Gedmatch users want, need, or expect. (I have “sanitized” my results example.)
- Now – open a new spreadsheet on your computer (I used Excel). I input the chromosome number from #1 all the way to #22 (the X-Chromosome – #23 – is a whole different ballgame so for this instruction, I’m not going to mention it).
- Go back to your Gedmatch results page and click on the first kit number (left hand side) of your first match. This brings up the autosomal comparison. What you are looking for is the chromosome with a lot of blue.
- Once you find that chromosome (or more), open your snipping tool and snip that entire line. Instead of saving that as a .jpg, just right click directly on that snipped image of the chromosome and “copy”. Switch back to your spreadsheet and “paste” it in the correct chromosome position. Now go back to the autosomal comparison and snip the information box above the chromosome you snipped (it should have the chromosome number, start location, end location, centimorgans, and SNPs). Do the same to copy that box and then paste it on the same line as the copy of the chromosome string. Do that however many times you need (if there are more than one matching chromosome). Before you finish, you will want to go to the top of the autosomal comparison and copy and paste the information for the DNA kit number and name of the person you match. Then paste that to the side of your chromosome string in your spreadsheet.
- Now the really tedious part is clicking on the Gedcom ID for the match you were just working on.
A new tab (or window) will open with the Individual detail. At the top of that, click on pedigree. The default is 5 generations (shown at the top left). 
Unless you can automatically see who the shared ancestor could be, I suggest entering 10 in the box for the number of generations and click submit. (Personal note: I’ve been entering 15 generations). Once that very lengthy pedigree chart opens, carefully go through it to find your shared ancestors.
If you are lucky and find them, go back to your spreadsheet and enter the names of the shared ancestors under where you have pasted the DNA kit number and name. It also helps if you list if the ancestors are on your paternal or maternal side.
- Now the fun begins – do that with every single one of your matches. Pretty soon, you will see some chromosomes that appear to be shared between your matches. In order to see if they really do share DNA with each other (as well as you), go back to the Gedmatch Home screen (I usually have several tabs open so I don’t lose my Gedcom kit match screen). Under DNA raw data, click on “One-to-One compare”. On the next screen, you will enter the DNA kit number from one of the matches and another kit number to compare (you will have to refer to your spreadsheet for this information). Before you click “submit” – make sure you have clicked on “Yes” for “show graphic bar for each chromosome.” When the results appear, check if the two that matches you – also match each other. They may not. If they do, you will want to create some sort of key on your spreadsheet in order to see at a glance that they match. I do this by changing the color of the font over the name/kit number.
Notice above that the first three rows of my Chromosome #1 are all close to the same cMs. Those three also match each other as well as matching me (I have colored the names/kit numbers blue). My biggest problem – not finding a shared ancestor in any of them! The graphic below shows four matches to me on Chromosome #2. 
Even though the bottom two appear to be close to the same string and cMs – they do not match each other – nor do they match the top string – and I can’t find shared ancestors on any of them! Then the following graphic for Chromosome #10 shows three matches to me and all three match each other. I did find the shared ancestors of Richard Lyman and Sarah Osborne on all three! 
- How this can help you is if two of your matches do not match each other but are for the same cMs, one could be on the paternal part of that chromosome and the other the maternal part.
Disclaimer: I am not a scientist. I am not very literate when it comes to DNA and triangulation. I do not have the answers. I am still scratching my head about some of the matches – same string, different shared ancestors. I do not know who many of my 3rd-4th great-grandparents are and therefore am sure that it’s not that I can not find the matches, but I just don’t know who to be looking for! Just because you “find” the shared ancestor(s), does not mean their (or your) Gedcom is accurate. A wrong spouse’s name, wrong parents’ names, or wrong dates can throw you off as well.
What I have discovered: I found matches on people that up until now were only relatives because they “adopted” or “fostered” an ancestor so I’m left wondering if there really was a familial connection to begin with or I’m just missing something. I’m also finding many matches that are in parts of the country where I can’t place my ancestors. I have many more matches on the paternal side of my family than on my mom’s side but I think the reason is because not many people on the maternal side have A) Not taken a DNA test, B) Not uploaded their raw DNA data to Gedmatch or C) Have not uploaded a Gedcom even if uploading raw DNA data.
I hope this helps some of you who are curious about “what else you can do” with your DNA information. It’s been very eye-opening and interesting and fun for me!
All My Branches Genealogy 
I do think that “adoptions” and “fostering” were often between family members. I worked with a woman who found out (as an adult) that her bio mother were her “adoptive” parents teen sister. Instead of the shame of a out of wedlock pregnancy, girls and women were sent to a relative who was “convalescing” I also know someone who found that an aunt had “adopted” her mother and two uncles after the grandmother’s divorce.