I know I am a little late to this party also…
The first step in is usually to define the need which may not always be obvious. In other words, how does someone benefit from its inclusion?
There are two types of users who are interested in this information.
(1) Those that have trees use the DNA results as evidence, just as a birth or death certificate does. We form an opinion as to the degree of confidence in those connections based on the current evidence at hand. Maybe we have something like a DNA Report; we create, and cite the DNA Report as the DNA Evidence.
(2) Those that do not have trees, and use the DNA results to provide direction in finding a way to connect their part of the tree to others on Wikitree.
The prior presumes they have a Wikitree connection to other DNA Testers, while the latter presumes there is no connection in Wikitree… Yet!
You do not need triangulation to have confidence in a connection. You use triangulation as a measure of confidence. For example, 23andme, FTDNA, and AncestryDNA will predict a relationship, and a range. Gedmatch will predict a genetic distance. If these predict that a parent/child relationship is a parent/child relationship that should be sufficient. If two people have a paper trail showing they are 4th cousins and there is a prediction they are in the range of 3rd to distant cousins, this is supporting evidence of the relationship. The confidence level may increase as more DNA Testers get tested.
The real value of triangulation is to prioritize and focus a DNA Tester’s attention to finding a common ancestor with another DNA Tester.
The first step is to identify those who are related by blood (DNA Matches), using the results of the different DNA services. The next step is to prioritize by ordering the list by genetic distance with the intent of locating their tree. Let’s presume this is outside the scope of Wikitree.
Let’s presume now the Adoptee has access to one of those DNA Testers profile. The Adoptee now compares his list with a Wikitree list of those DNA Testers identified as blood relatives who could possibly share any DNA for Wikitree DNA Tester identified. Let presume that Wikitree identifies those Testers. In other words, You know you want to concertate on those you know have a tree and you begin with the closest matches first.
Then the adoptee compares his DNA with those who are listed on Wikitree as blood relatives. This comparison is done outside the scope of Wikitree. The Adoptee is motivated to extend the Wikitree by adding to the decedents of the common ancestors in the hopes one of the paths will lead to him. He is trying to complete the triangles that include him. In other words, since he knows he is related to two people, a good starting point is to focus on their common ancestors.
Understanding Segment Triangulation…
A segment is identified by a starting and ending location on a Chromosome. The distance between them are measured in cM's. Let’s say that 3 adoptees (A, B, C) state they have segments of at least 7 cM’s that overlap among the three of them… There are 3 segments A/B, B/C and A/C.
The overlap of these three segments infers a 4th segment. The Triangulated Segment (TS). The location of this segment begins at the highest starting position and the lowest ending position of the 3 segments. In other words, the Triangulated Segment can be from 1cM to 7cM in length.
A Triangulated Segment cannot be used to IDENTIFY a PARTICULAR Common Ancestor.
For example, three first cousins to each other share 2 common grandparents. The Triangulated segment can Identify the cousin parents they inherited this segment from, but there is no way to determine which grandparent passed this Segment onto their children.
Another example, aTriangulated Segment indicates Adoptee A, B, and C share “A” Common Ancestor but Adoptee A may share a different Most Recent Common Ancestor (MRCA) with Adoptee B, than with Adoptee C.