How to Triangulate

Here is a 3-step process for Triangulation: Collect, Arrange, Compare/Group.

  1. Collect all the Match-segments you can. I recommend testing at all three companies (23andMe, FTDNA, and AncestryDNA), and using GEDmatch. But, wherever you test, get all of your segments into a spreadsheet. If you are using more than one company, you need to download, and then arrange, the data in the same format as your spreadsheet. Downloading/arranging is best when starting a new spreadsheet. Downloading avoids typing errors, but direct typing is sometimes easier for updates. I recommend deleting all segments under 7cM – most of them will be IBC/IBS (false segments) anyway, and even the ones which may be IBD are very difficult to confirm as such. You are much better off doing as much Triangulation as you can with segments over 7cM (or use a 10cM threshold if you wish), and then adding smaller segments back in later, if you want to analyze them. NB: Some of your closer Matches will share multiple segments with you – each segment must be entered as a separate row in your spreadsheet. The minimum requirement for a Triangulation with a spreadsheet includes columns for MatchName, Chromosome, SegmentStartLocation, SengmentEndLocation, cMs and TG. Most of us also have columns for SNPs, company, testee, TG, and any other information of interest to you. Perhaps I need a separate blog post about spreadsheets… ;>j
  1. Arrange the segments by sorting the entire spreadsheet (Cntr-A) by Chromosome and Segment StartLocation. This is one sort with two levels – the Chromosome column is the first level. This puts all of your segments in order – from the first one on Chromosome 1 to the last one on Chromosome 23 (for sorting purposes I recommend changing Chromosome X to 23 or 23X so it will sort after 22). This serves the purpose of putting overlapping segments close to each other in the spreadsheet where they are easy to compare.
  1. Compare/Group overlapping segments. All of these segments are shared segments with you. So with segments that overlap each other, you want to know if they match each other at this location. If so this is Triangulation. This comparison is done a little differently at each company, but the goal is the same: two segments either match each other, or they don’t (or there isn’t enough overlapping segment information to determine a match). All the Matches who match each other will form a Triangulated Group, on one chromosome – call this TG A (or any other name you want). Go through the same process with the segments who didn’t match TG A. They will often match each other and will form a second, overlapping TG, on the other chromosome – call this TG B. [Remember you have two of each numbered chromosome.] So to review, and put it all a different way: All of your segments (every row of your spreadsheet) will go into one of 4 categories:
  • TG A [the first one with segments which match each other]
  • TG B [the other, overlapping, one with segments which match each other]
  • IBC/IBS [the segments don’t match either TG A or TG B]
  • Undetermined [there are not enough segments to form both TG A and TG B                            and/or there isn’t enough overlapping data to determine a match.]
  • NB: None of the segments in TG A should match any of the segments in TG B.
  1. At GEDmatch – the comparisons are easy. Just compare two kit numbers using the one-to-one utility to see if they match each other on the appropriate segment. The ones that do are Triangulated. You may also use the Tier1 Triangulation utility or the Segment utility. I prefer using the one-to-one utility and Chrome.
  1. At 23andMe you have several different utilities:
  • Family Inheritance: Advanced lets you compare up to 5 Matches at a time. You may also request a spreadsheet of all your shared segments; sort that by chromosome and SegmentStart, and check to see if two of your Matches match each other. The ones that do are Triangulated.
  • Countries of Ancestry: Sort a Match’s spreadsheet by chromosome and SegmentStart, search for your own name, and highlight the overlapping segments. The Matches on this highlighted list who are also on overlapping segments in your spreadsheet are Triangulated (the CoA spreadsheet confirms the match between two of your Matches)
  1. At FTDNA it’s a little trickier, because they don’t have a utility to compare two of your Matches. So the most positive method is to contact the Matches and ask them to confirm if they match your overlapping Matches, or not. The ones that do are Triangulated. An almost-as-good alternative is to use the InCommonWith utility. Look for the 2-squigley-arrows icon next to a Match’s name, click that, and select In Common With to get a list of your Matches who also match the Match you started with. Compare that list of Matches with the list of list of Matches with overlapping segments in your spreadsheet. Matches on both lists are considered to be Triangulated. Although this is not a foolproof method, it works most of the time. And if you find three or four ICW Matches in the same TG, the odds are much closer to 100%. Remember, every segment in your spreadsheet must go in one TG or the other, or be IBC/IBS, or be undetermined. If a particular Match, in one TG, is critical to your analysis, then try hard to confirm the Triangulation by contacting the Matches.
  1. AncestryDNA has no DNA analysis utilities. You need to convince your Matches to upload their raw data to GEDmatch (for free) or FTDNA (for a fee), and see the paragraphs above.

Comments to improve this blog post are welcomed.

 

10 Segmentology: How to Triangulate; Jim Bartlett 20150511

57 thoughts on “How to Triangulate

  1. Regarding triangulation at. FTDNA is using the matrix tool not an option? …load the two that match you in the tool to see if they match each other. also having a parent’s kit to determine side of family on which you match is extremely helpful.

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  2. The FTDNA matrix tool is a different way of looking at In Common With, and it can be used instead. A parent’s kit should not be used as one “side” of the Triangulation. After the Triangulated Group is establish, a parent’s kit is invaluable in assigning the TG to that side (parent).

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  3. Thank you so much for putting this out for all of us to read. The fact that there are two of each chromosome, and that not everyone that looks like a match really is, is not well explained in most of the literature I have read.
    I look forward to all your future posts. Thank you again.

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  4. if I match someone on multiple chromosomes, in order to triangulate – do I need to have a 3rd person that also matches on all the chromosomes, or just one??

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    • David,

      Each shared segment is potentially from a different Common Ancestor, although usually multiple segments from one Match (usually a close relative), will be from the same, close, Common Ancestor. Each shared segment in a different location, on a different chromosome or not, should be part of a unique Triangulated Group. You need at least one other Match for each one. It will usually be different Matches for different TGs, but it could be the same one. The ones who also match on multiple TGs tend to be very close cousins/relatives. So you need just one, for each Triangulated Group.

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  5. wow – thank you for the quick response. so to paraphrase, I need just one chromosome; but it’s worth creating a triangulated group for each to establish other possible CA’s. I very much appreciate your answer. it’s helped my understanding quite a bit.

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  6. I have another question. can I triangulate using 2 knowns? in other words, can I use myself and my father and one other unknown person. then if that person matches me and that person matches my father, then I’m triangulated??

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    • Jim – I was about to ask this question but remembered that I had asked it before. if you have a moment, can you respond to above (reposted below as well)??

      “I have another question. can I triangulate using 2 knowns? in other words, can I use myself and my father and one other unknown person. then if that person matches me and that person matches my father, then I’m triangulated??”

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      • David

        You can do that (use yourself and a parent), but take care. Since you and a parent are fully identical, it like just sharing a segment with someone, and knowing it’s on one parent’s side. If the shared segment is less than 10cM, it might be IBS (and your parent may still match). So you are much better off triangulating with two widely separated cousins – such triangulation is almost always IBD with segments over 7 cM.

        Jim – http://www.segmentology.org

        >

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  7. I downloaded all of my FTDNA matches into Excel, sorted by cM and eliminated everything under 5.0, then sorted the way you recommended. I had previously sent all of my Ancestry and FTDNA to GEDMatch. Next I asked GEDMatch for a one-to-many and printed the full list of my 1,500 matches. I don’t need to concern myself with the lack of raw data from Ancestry since GEDMatch provides it. At that point things get tedious. Using the “two kits match” utility, I can get a list of other matches in a family group. I finish up that list with a one-to-one match and enter the data into the appropriate chromosome/start/end spot in my spreadsheet. While this sounds as if it makes sense to me, and the results look reasonable for known cousins, I would appreciate your review. I don’t want to spend hundreds of hours going down the wrong path, and you are the only person I trust with an answer.
    Thanks,
    Don Sheaffer

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    • Don

      What you are doing is correct. This is the collect and arrange steps. Now you need to group them. Determine which overlapping segments match each other. In general, for each area on a chromosome you’ll form two groups – on for each parent (although you may not know which parent, yet).

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      • Jim, Thanks for taking time out of your busy schedule to reply. That explains why I got hits on the same chromosome at the same segment start location for both paternal and maternal cousins. At some point along that segment they must have crossed, right? Don

        Liked by 1 person

      • Don I’m not sure what you mean by crossed. Segments do not “cross”. Segments are formed between crossover points – when a parent recombines his or her two chromosomes to make a new chromosome for a child.

        Jim – Sent from my iPhone – FaceTime!

        >

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  8. Pingback: Shared Chromosomes and Triangulation Part 1

  9. Hi Jim… I’m using all segments from Gedmatch and adding additional matches from FTDNA then using a filtering out the smaller segments. I have a few matches from FTDNA which comprise of several small segments only. Should I consider these as true matches and when are they useful?

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    • Jeanette, Yes, you can use them if you are sure the shared segment is IBD. I don’t know of any way to insure short segments are IBD. The algorithms can make short segments “look” like they match. So be careful, and ready to “delete” if you get contrary evidence…

      Jim – Sent from my iPhone – FaceTime!

      >

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  10. Thanx a bunch! That brings me to another question. These matches don’t qualify using the gedmatch criteria and probably would not make my list on Ancestry. Why does FTDNA consider them as matches? Is it simply because totaled they meet their criteria as a match? I guess no algorithm is perfect in genealogy. I think I’m just trying to understand the logic of them being on my FTDNA match list before I delete them.

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  11. Checking on when I can declare victory. Using DNAGed.com as my focus, I have identified an area where there are 4 people who match each other and myself. 2 of these people had posted genealogy trees that showed a match based on the tree. I contacted the other two. The first one to get back showed the same genealogy tree match.

    All the shared segments are about 12 cM. Each person has a total match with me in excess of 30 cM.

    The hypothesized relationship is a 4th cousin plus a 5th cousin (my paternal grandparents were 2nd cousins, once removed, from the same couple involved in this match).

    Time to declare a successful triangulation and move on to the next challenge?

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  12. Dear Jim,

    I have one that is baffling my mind! In doing research to find my father, i came across a NPE. My mothers brother and sister are both half siblings. I have my mother’s other sister’s daughter test (my cousin) All of my Aunts and uncles have the same mother, this i am sure of, its the father in question. How do i triangulate the four of them to see if my cousin’s mother is a full sibling match to either my mom, or her brother and sister. I suspect my cousin’s mother (who couldnt test) is my mom’s full sibling. I just cant wrap my head around proving it. They all triangulate on my grandmothers side, How do I see the difference on the paternal side. Sorry if I am messing this up…
    All have gedmatch, and FTDNA.
    Feel free to email me directly
    mcostantakos@gmail.com
    Melanie

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    • Melanie,

      You triangulate folks by finding common Matches on overlapping segments. Perhaps make a spreadsheet of all the Matches and segments for each one – include a column for the initials of the base person in each case. Then combine the four spreadsheets and sort on Chromosome plus Start Location and look down the list for Matches who appear near each other.
      A different plan is to upload all of their kits to GEDmatch and then compare them to each other. Full siblings will share twice the DNA as half-siblings.
      Jim

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      • Thanks Jim,
        Its a cousin match though. My mother and this cousin (who’s Mom I hope is my mom’s full sibling) share 1600 cms, and 160cms of it are an X. My mothers half siblings match this cousin (or their niece) at about 1100 and 1000 cms, and only have about 50 cms of the X. So I think that her mother would be a full sibling match to my mother. All are uploaded to Gedmatch. Mom – A690123, Laura (Cousin) A505275. Patty -A982500, and Eddie F412372.
        Melanie

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  13. Hi Jim,

    Many thanks for this blog! Your clear, simple explanations are a great reference–I’ve read each post more than once and I look forward to future posts!

    I am experimenting with forming TGs on Chromosome 1 and I have a couple of questions. I created a spreadsheet of my GEDMatch matches, sorted by chromosome and segment start/end points. I then created groups (large for now) of the overlapping segments on each chromosome.

    1. I have results for both my parents. You mentioned forming triangulation groups first and then using parental results to assign the groups to maternal or paternal. I have results for both my parents and intuitively it seems that I should separate out maternal and paternal matches first and then create triangulation groups within each of those lists. Are the initial designations of TG A and TG B to separate out the maternal and paternal chromosomes? (I understand that I don’t use myself and a parent to triangulate, but does it make sense to make a first division of segments by separating my maternal and paternal matches?)

    2. I have a fairly large number of segments on Chromosome 1, 39/156, or 25%, that don’t match either parent. All of the non-matches are under 9.0 cM. Are those segments IBS and is that number typical?

    Warm regards,
    Terri Jensen

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    • Terri – Thanks for the positive reinforcement. Triangulation is designed for everyone, and all you have to do is compare segments to see which ones match each other. This part is fairly straightforward, creating TG-As and TG-Bs. The next step is using genealogy to assign the TGs to Maternal and Paternal sides. When you know either parent, or both, you can go directly to TG-M and TG-P.

      1. As you form TGs, if the segments also match one parent or the other, you know directly if the TG should be TG-M or TG-P. And as you point out, all the segments that also match your mother can be set aside for TGs on the Maternal side (same for matches with your father on his side). In this case all that is then needed is to determine where one TG stops and the next one starts (remembering that segment ends are a little fuzzy, so there may be a small overlap; and/or there may be a gap between TGs). The key is that no segment in one TG will match a segment in another TG (except close cousins may share large segments which span several TGs). The order things are done is not important – each TG comes from a specific Common Ancestor. Whether you figure out which side the segments are on first and then group them into TGs, or form TGs first and then figure out which side – it doesn’t matter.

      2. You are also correct that a high percentage of segments at GEDmatch from 7 to 9cM are false. GEDmatch has no screening method in their algorithm (like other companies have), so all of these segments are presented to you as a “match”. As a tip, I usually drop the matching criteria to 500 SNPs and 5cM to check these segments against a parent – sometimes they have 690 SNPs (just under the 700 threshold), or 6.9cM (just under the 7.0 threshold). Those that then match a parent with this lower threshold, should be compared, using the lower threshold, against other segments in the appropriate TG – most will match, and may then be included in the TG.

      3. And one other observation. Sometimes I write about comparing Matches. I should always say compare segments. I have found a small number of Matches with two segments, and one segment triangulates on one side, while the other segment triangulates on the other side. In other words those Matches will share two different Common Ancestors with you – one on each side. This can also happen on the same side, which highlights the concept that the Common Ancestor for each TG has to be determined independently. If a Match shares multiple segments with you they will usually be from the same Common Ancestor, but not always. So be aware.

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      • Thank you for your reply, Jim. This all makes sense.

        With respect to #2 above, yes, that worked! In my first TG on Chr 1, lowering the threshold as you suggested showed the “no matches” to be maternal matches (which I would have expected because those “no matches” matched others in the TG), just under the original threshold. That also cleared up why some of the maternal matches in that TG on Chr 1 didn’t match each other (they all matched when I lowered the threshold). I confirmed the matches using my maternal phased results from GEDMatch (with lower threshold), too.

        I think I dived in too quickly to an area of short segments where it’s trickier to understand what’s going on. Two of the people in the above maternal TG have also tested on FTDNA, where they match me (but not my Mom), and aren’t ICW each other. But one is ICW a “new” FTDNA person (not on GEDMatch) who matches both Mom and me within the TG, on a 22.56 cM segment, so that’s a possible lead. Though most of the segments in this TG are small and the CA probably distant, this particular group is exciting to me because I know one member of the group to be from somewhere on my Mom’s “recent immigrant” side, where I have few matches and am at the brick wall.

        This is fun! With experience I’m sure more will become clear. Time to work through some more chromosomes and TGs with longer segments and a known CA or two. Thanks again!

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  14. Your site is a breath of fresh air, a bringer of clarity to the fog of genetics that swirls around us newbies.

    I need confirmation that if I share a specific segment over 10cM with two different matches on two different test sites that the three of us must triangulate on a common ancestoral line but not necessarily the same MRCA. True/false?

    As an example, a recently discovered 2nd cousin matches 5 of us close family in the followng way

    Start End
    My 1st cousin 1 24000000 49.8 cM 9144 SNPs
    Same cousin 27000000 33000000 7.6 cM 1294
    Another 1st cousin 1 8000000 19.4 cM 3630
    My brother 1000000 24000000 46.5 cM 8549
    Same brother 27000000 32000000 6.7 cM 993
    My son 1 15000000 33.0 cM 6270
    Me 1 24000000 49.8 cM 9139
    Me again 27000000 31000000 6.5 cM 892

    Now if I find matches on any other site including GEDmatch and DNAGedcom, that start on chromsome eight at 1 that they are definite triangulated matches if they exceed 10cM. If that chrm match is not the strongest match then it is still a decent confirmation.

    If the matches exceed 10 chr but don’t start and/or end at the same point on the chr are they still triangulation matches?

    If a different invidual matches me at two smaller fragments me within the start and end point of a larger segment, such as the fragment of chr 8 starting at 1 above, can I tentatively include that as valid match that has only been broken by recombination along their ancestral line?

    Thanks for your help. I’m expecting your response to enable me to sleep better. Not that I want to put any pressure on you or anything like that.

    Ian “McCallum”

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    • Ian – a long complex example with a lot of questions. Some of your shared segments don’t have Chr # and both start and end locations. But if I get the gist of it, you have overlapping segments which match each other. And they are on the same side of your family. Then they should share a Common Ancestor with you. Some may be closer cousins (with closer MRCA), but all of the CAs will be on one ancestral line of yours.
      The shared segments do NOT need to start or end at the same location; and one can be included in another. They should overlap each other roughly at least 7cM by an eyeball estimation. The key is that they match each other. Hope this helps.
      Sweet dreams…

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  15. Thanks for the reply Jim. It clarifies a number of questions that I had.

    It looks like I wasn’t clear enough about two important specifics (chr number #8 and start/end points), the latter compounded by the table’s format collapse.

    First specific, the examples are all how my recently discovered 2nd cousin (Karen) matches with these five male members of our family on chromosome 8, There are 5 of us: 2 of my 1st cousins, my brother and my son. That explains why there is so much consistency between the lines, for example four of the lines start right at, the beginning of chr8, @1.

    The analysis comes from 23andme.

    My larger question concerns a “third” party, one not included here. If that party has the same or a large portion of the same chr 8 fragment, can I then assume that this new match is also related to my 2nd cousin Karen, since she too matches me on that fragment? I assume so, but I need confirmation of that point so that I can confidently use it to produce a short list of matches to contact.

    I hope that clarification helps.

    Ian “McCallum”

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    • Ian,
      Just having the same segment area is insufficient. Both your maternal and paternal Chr 8 have that area. The “third” party has to match at least two of the others in the group.

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  16. Thanks Jim. So I assume then that anyone else who matches Karen and me on that fragment at the same lab can be used to triangulate with third parties, say on GEDmatch . Using close relatives is not absolutely necessary. Useful. Thanks. Keep up the excellent work.

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  17. For my simple brain:
    a “match” is someone who shares a large enough amount of DNA with you to be identified as a potential relative.

    a “match segment” or “matching segments” are the pieces of that shared DNA, identified by a beginning and ending location number on a chromosome.

    “triangulation” is when three or more people who match each other (are matches) share the same matching segment.
    Right?

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  18. I have a group in my match list that I don’t know what to do with. I ran the triangulation function at Gedmatch and came up with the following on chr 1.

    A762411 A443210 3,310,659 11,502,057 16.6
    T093771 A762411 5,197,705 14,367,590 17.7
    T093771 A443210 5,465,256 11,502,057 10.7
    M485905 A443210 7,073,164 11,502,057 7.4
    A762411 M485905 7,073,164 14,362,549 13.9
    T093771 M485905 7,073,164 18,555,636 23.9
    A443210 A024222 7,408,904 11,717,263 7.4
    A762411 A024222 7,408,904 14,367,590 13.3
    T093771 A024222 7,408,904 18,299,732 22.3
    M485905 A024222 7,408,904 18,299,732 22.3
    A443210 M173836 9,457,890 11,719,611 4.1
    A443210 M173836 12,058,113 13,654,784 3.2
    A762411 M173836 10,407,606 14,365,065 8.9
    A024222 M173836 10,407,606 18,339,740 18
    M485905 M173836 10,407,606 18,555,636 18.9
    T093771 M173836 10,407,606 18,606,731 19

    There are 6 different people here that all match each other, and me of course.. But if I just take the common segment with all of them combined I only get a segment from 10,407.606 to 11.502,057 which is very small. How should I separate these into different groups? Or is each line a separate group?

    I have not yet contacted any of these people to find common ancestors. I am just trying to understand the concepts here.

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    • Dean – We need to understand each other. When you say they “all match each other”, I don’t get it, because I don’t think the first one and the last one will match (it doesn’t look like they overlap by 7cM). So do you mean you compared each one to each of the others? Matching doesn’t mean they are all on the same chromosome – it means they are compared to each other and they share a segment with each other on Chr 1 in this area. So the concept here is to compare the first two to each other – if they match on the same segment area they are a TG; if they don’t they are in separate TGs. Then compare #3 with one or the other until it fits with one. As you go down the list, each succeed one will match one TG or the other TG or neither (in which case it’s a false segment – usually under 10cM. In the end, with the group above, you’ll probably get two TGs, but you might get one TG on one side and two adjacent ones on the other side. Hope this helps.

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      • This list came from the triangulation group function at Gedmatch, so each line triangulates with me. This means that at the base level each line is a triangulation group on it’s own. I think I am understanding this part correctly; if not please correct me.

        When I say they all match each other, I mean that each kit matches every other kit at some point in this list. A762411 matches A443210 and T093771 and M485905 and so on for every other kit in the list. And carrying this on, every kit matches every other kit in the list. Every combination is there. Wouldn’t this mean they all match on the same chromosome of my pair of chromosome 1s?

        I guess it will probably become apparent what is going on here if I can get anyone to reply to email, but that’s proven pretty difficult so far.

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  19. Dean, generally the TG is not just the small overlap of all shared segments; but is from the smallest start location to the largest end location. Generally… You had to get this segment, intact, from an ancestor in order to match each of the others in the TG.
    In looking over your list again, I am very surprised that GEDmatch reported a 3.2cM segment.

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  20. Hello, I was wondering what a triangulation spreadsheet looks like? Do you create a separate spreadsheet for your TGs? If not, how do you handle segments that might need to be split into multiple TGs, do you just manually split them and create a new row in your spreadsheet for the same person?

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    • I have a master spreadsheet with every Match and segment over 7cM. I sort it by Chr# and start location. As I form TGs I give each of them a unique name (I have about 400 TGs over 45 Chrs.
      Yes, when a close cousin spans more than one TG, I copy that row and insert it in following TGs, and modify the new row(s): change the start location to the start location of the next TG; and add a note that it is a partial segment from the previous TG; and I highlight that note with a distinctive color (so I don’t mistake it for an original segment in its own right.) Usually, I know the CA for these closer cousins, and that CA carries over to the TG we are now talking about. NB: the CA for these two (or more) TGs may well be different and somewhat more distant, but these more distant CAs will each be ancestral to the CA (really an MRCA) you have with the close cousin.

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  21. Jim
    Thanks again for your earlier guidance on forming triangulation groups. I have completed the spreadsheet I sent and am working on getting additional data from my Montenegrin grandfathers family in order to build a more robust picture of that side of my tree.
    Now that I am hooked on Segmentology I have embarked on the next more complex part of my family.
    As background information I followed the following process.
    The Saucier (my father) side of the family came to Quebec city in approximately 1680. One of his 2 sons ended up in Mobile Alabama (at that time a French territory) and the family has been in the gulf coast ever since. There was a large influx of French Acadians and it seems many of the descendants are taking to DNA testing creating a rather large base of cousins.
    Using my fathers 1/2 brother as a base I ran the GEDMATCH Tier 1 Matching Segment Search and Triangulation (old version) utilities. I then uploaded the GEDMATCH data to DNAgedcom and ran the Autosomal DNA segment Analyzer (ADSA) tool to create my base Triangulation spreadsheet. (Min seg length 10cm Min SNPs in a seg 500)
    This report has 1800 rows. In order to isolate the potential Saucier cousins I went thru and deleted all entries that did not contain a TG that matched either me, my sister’s daughter or my brothers son as I don’t have DNA for my father.
    In starting assign TG’s to the remaining entries I have run into the following.
    In CH#2 I have a large group of shared segments 62 rows) that overlap. The largest segments are mine, my niece, and my nephew all overlapping with my 1/2 uncle.
    Using your divide start and end by 1,000,000 suggestion the segments are:
    Start End
    Me 4.27 42.16
    Niece 4.13 42.63
    Nephew 4.13 42.19
    Most of the other 62 rows fall within the range of 4.13 to 42.63 but there are some that overlap the start and others that overlap the end.
    Start End
    example 1 3.08 8.08
    example 1 37.6 46.39
    I have several of these overlaps and am looking for some guidance in including these overlaps when assigning TG’s
    My other sheet the segment overlaps were generally cleaner as I did not have so many segments.
    Thanks again for sharing your insights
    Doug

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    • Go with the overlapping segments and TGs for the base person. They may well extend beyond other close relatives, because each person is unique. Each descendant will have their own chromosome map, and will not get exactly the same segment from an ancestor. This is why you pick a base person to work with (usually yourself). NB: even for the base person, the end of each TG may overlap the next TG by 1 or 2Mbp – just chalk that up to fuzzy data and ignore it. Your goal is establish all the TGs you can – create the big picture – even if you don’t know the CAs. Once all the puzzle pieces (TGs) are established, you can work with the Matches in each TG to find more and more distant CAs.

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      • Jim
        That is the reason I used my 1/2 uncle as the base for this side of my family. My father and my uncle share DNA from my grandfather. My grandmother’s side of the family is from the northeast and my grandfather is from the south. My father’s family has been in the gulf coast for 350 years. I am very confident there is not much chance of any crossover based on all of the family research to date. I am making progress creating TG’s for the Saucier’s using your suggestion.
        Thanks again Doug

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  22. Jim
    I have been following the conversations about your 23andme triangulation tidbit especially the difference between ICW and TG. That clarification should be in every discussion as I have seen the confusion and even experienced it myself. I got clarity on the subject as I expanded my research into my domestic relatives. After I ran my first set of GEDMATCH reports and was looking at 1800 plus “matches” I began to look into more automated tools to help me build my TGs. What I found was DNAGed.com and their GEDMATCH upload and Autosomal Analysis tools.
    DNAGedcom uploads the GEDMATCH tier 1 Shared Segment and Triangulation (not the beta one) reports into a database and allows you to run an Autosomal Analysis report that gives you two forms of output. One output is a web page that gives a very colorful by chromosome report showing the ICW’s across chromosome representation and within the chromosome the “bricks as they call them) turn out to be Triangulation groups.The other report is the same data but in a form that can be loaded into a spreadsheet. I have performed this process for each of 8 of my relatives and tested the output with the GEDMATCH 1 to 1 and 1 to multiple kits on a random basis on many of the bricks and they are true TGs. Now I am using this process and creating my TGs by modifying the spreadsheet output to be my base documents for my TGs. I have to modify the output to suit my needs but this has saved me untold hours of manual work and is probably more accurate than my manual work. You might want to look into this and I would gladly share my spreadsheets with you as a start. I think this is superior to the 23andme process and I think DNAGedcom is working on a 23andme loader as well.
    Thanks for all your help you have clarified a lot for and I am still learning.
    Doug

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    • Doug, thanks for your comments. In 2010 when I first got 23andMe and FTDNA atDNA tests, I put on my genealogy hat and contacted just about every Match over the next two years. Most of us hadn’t a clue about how to use atDNA. When I got to about 100 Common Ancestors, c2012, I realized I needed a spreadsheet to keep track – but that first spreadsheet didn’t include segment data, just CAs. Gradually I added info on the Chr and location. Somewhere in all that, and the email groups, and folks that knew much more than I did about genetics, someone mentioned Triangulation (not me). I started looking at that concept – I’ve been an engineer for 50 years – and I became hooked. I quickly added segment data, and realized the importance of my Dad’s atDNA. And determined that about 1/4 of my CA’s were wrong. So my spreadsheet evolved. Today the main part of it, with IBC culled out, is over 12,000 rows, from over 8,000 different Matches, with over 500 CAs that “fit”.
      I’ve learned a lot from doing this by hand. I now have a “feel” for segments, and can predict the side almost every time. I see patterns, natural break points, overlaps, etc. that would not be as obvious if I’d have just pressed a button and gotten the spreadsheet. I’m familiar with my data, and it “talks” to me. I’ll be posting some of those findings in due course.
      By hand Triangulating each new Match, I see where it fits AND whether it’s just another block in the wall, or whether it offers a new insight. I have fallen behind on my goal to contact every Match, but I’m contacting most of the new key ones. I make myself shift into genealogy mode regularly – hidden in even the average Match-segments are genealogists with good Trees and a willingness to work together to find CAs.
      I have used DNAGedcom to create spreadsheets that I can input. I then append them to my Master spreadsheet, sort the whole thing, and then work down all the rows, looking for duplicates. This is also a Quality Control check and update – fixing a few errors I’ve made, as well as some data that gets changed at the companies over time (including name changes, and segment “updates”). It now takes days for this process. I need a better process for deleting only the new rows that are clearly dups – I have my own info on most rows and don’t want that deleted – ideally I’d like all the dups to be moved to a “trash” spreadsheet so I can quickly scan all those rows and confirm I’m not discarding anything important. I think that’s the next great tool for updating a spreadsheet.

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  23. Jim,
    I’ve been dabbling my toes in this for the past two and a half years, but now it is time to get serious. I understand the concepts, but there are so many I have a difficult time know where to jump in. I finally have all 15 of my cousins, a half uncle, two children and a grandson loaded into GMP, but then I’m not sure what I should be doing next. Is there a methodology that would help me delineate what specific steps I should be taking next. Sort of like instead of thinking “clean the kitchen”, you instead break it into items, i.e. put away leftovers, gather all dirty dishes, load them into the dishwasher and start it, wipe down the stovetop and counters, sweep the floor, mop the floor, etc..

    Also, I noticed on gedmatch.com they now have a Tier 1 tool for Triangulations Groups, but there is no explanation for how to interpret the results, and unfortunately for me, I am not intuitively understanding the results.

    Any words of advice would be greatly appreciated.

    Meg

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    • With GMP they should already grouping segments. You can use the GEDmatch Triangulation utility to verify which overlapping segments are in groups together. Then work with a TG. Pick one with a known relative. Then work with the Matches in the TG to find a Common Ancestor. Look at their Trees where you can. Email them a link to your Tree. It’s all genealogy at this point. So in summary: Step 1 form TGs; Step 2 select a TG to work on; Step 3 work with the Matches to determine the CA; Step 4 select another TG; Step 5 = Step 3.

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