DMT Excel File - Map Page

 
The output of the DMT program is an Excel file that has two pages. DMT uses a technique called Excel automation to produce this file. If you do not have Excel on your computer, then DMT will produce one Comma Delimited file (csv file) that contains the same data but unformatted which you can load into any spreadsheet program, but you will have to then format it yourself.
 
The first page is the Map Page.
 
DMT Excel File - Map Page
1

Double Match Line

1. Double Match Line
 
Column A (NAME-A) is Person a, the person you are interested in whose ancestors you want to find.
 
Column B (NAME-B) is Person b, the person whose Chromosome Browser Results file is compared and double matched with Person a. In a single run of one Person a with one Person b, columns A and B will never change. But they are included so you know who was compared if you copy the results elsewhere or if multiple results are combined.
 
Column C (NAME-C) give the Person who double matches with Person a and Person b on this segment.
 
Column D (CHROMOSOME) gives the Chromosome number.
 
Columns E (START-AC) and F (END-AC) give the start and end base addresses of the Person a match with Person c. They are shown in green if they coincide with the start or end of the Double Match and are shown in red if they don't. The AC matches are what you see in Family Tree DNA's Chromosome Browser.
 
Column G (CM-AC) gives the length in Centimorgans (cM) of the match between Person a and Person c. For Double Matches that Triangulate, segments are almost all Identical By Descent (IBD) down to 5 cM and are only likely to be chance matches for shorter matches than 5 cM. Although studies of Missing a-b Double Matches have not yet been done, it appears they too may be valid (not by chance) Double Matches down to 5 cM. The second match requirement seems to be what eliminates the larger chance matches above 5 cM.
 
Columns H (START-BC) and I (END-BC) give the start and end base addresses of the Person b match with Person c. They are shown in green if they coincide with the start or end of the Double Match and are shown in blue if they don't. The BC matches are useful to indicate how closely related Person B is to Person C. Close relationships will have longer BC matches.
 
Column J (CM-BC) gives the length in Centimorgans (cM) of the match between Person b and Person c.  This value can help identify whether Person a or Person b is related more closely to the c people in a Double Match Group. That may provide clues as to the relationship between Persons a, b and c.
 
Columns K (DMG-START) and L (DMG-END) give the start and end base addresses of the Double Match Group (DMG) that is diagrammed by the thick box shown in the Map. The collection of Double Match segments that overlap each other define each DMG. Some larger DMGs may span smaller DMGs. Generally, the larger the DMG, the closer the ancestor is. Smaller DMGs within a larger DMG denote ancestors of the ancestor.
 
Column M (DMG-GROUP) gives names the Double Match Group using a notation designed by Jim Bartlett. For example, 01.170.183 refers to the Double Match Group that is on Chromosome 1, starts at a base address between 170000000 and 170999999 and ends at a base address between 183000000 and 183999999.
 
2

Segment Status

2. Segment Status
 
"Full Triangulation" is shown in green and means that Person a matches Person c, Person b matches Person c, and Person a matches Person b on at least some of this segment. If this is not a by chance match, then it indicates that Person a, Person b and Person c all received that segment from a common ancestor. The tricky part for you is to genealogically figure out who that ancestor was.
 
"Missing a-b Match" means Person a matches Person c and Person b matches Person c, i.e. a Double Match, but Person a does not match Person b on the segment. If this is not a by chance match, then it indicates that Person a matches Person c on one half of the Chromosome pair, and Person b matches Person c on the other half. One half might come from the father of Person c, and the other from the mother of Person c. Alternatively, both segment halves might have come from a common ancestor and were both passed down by two descendants to their child. See more discussion about these possibilities on my blog post: Triangulation and Missing a-b Segments). Small Missing a-b Matches might still be by chance, so you still have to be cognisant of that and look for multiple people matching on the same segment.
 
"Base a-b" is shown in yellow and shows where Person a matches Person b. Double Match segments that overlap a Base a-b match are defined to be Full Triangulation. Those that don't overlap a Base a-b match become the Missing a-b Matches.
 
3

Base a-b Line

3. Base a-b Line
 
This line, highlighted in yellow, shows a segment match between Person a and Person b.
 
Since Double Matches show where a segment of Person a matches with Person c, and Person b matches with Person c, any double matches that overlap with a Base a-b segment becomes a Full Triangulations.
 
All the people with segments overlapping the Base a-b segment become part of a Triangulation Group. All the people of the Triangulation Group received that same segment from a Common Ancestor or an ancestor of that Common Ancestor. Of course, that's assuming that the Person c match with Person a and Person b is not a random match by chance. Generally, 5 cM triangulated matches make chance matches very unlikely.
 
4

The Map

4. The Map
 
The right section of the Map page in the Excel file, from columns O to JD, provides a simple visual representation of the matches.
 
The numbers at the top represent the base pair addresses in millions (Mbp).
So, for example, 43 would represent base pair addresses between 43000000 and 43999999.
 
- The green X's show the Double Matches where Person a matches Person c and Person b matches Person c
- The red a's show Single Matches where Person a matches Person c
- The blue b's show Single Matches where Person b matches Person c
- The red a's along with the green X's denote the entire segment where Person a matches Person c.
- The blue b's along with the green X's denote the entire segment where Person b matches Person c.
- The green X's in the Yellow sections show where Person a matches Person b.
 
Only one color is shown in any cell. A green X will take precedence, so very small single matches that don't cross an Mbp boundary may not show up on the map. But they will show up in columns E, F, H and I.
 
5

Double Match Group

5. Double Match Group
 
Thick black boxes delineate Double Match Groups (DMG). The matching segments between Person a and Person c within a DMG all overlap. The a-c match includes both the red a's and green X's, but not the blue b's. This is because Double Match Groups are shown from Person a's perspective. The goal is to identify who each of Person a's DNA segments belong to. Doing so will help identify the relationship of the c people to Person a.
 
Longer overlapping DMGs (segments from closer ancestors) are shown first followed by the shorter DMGs (segments from more distant ancestors) that make them up. Double Match Groups are shown in order of their DMG-START and then by their highest DMG-END. Within the Double Match Groups, each match line is shown in order of their START-AC and then by their highest END-AC.
 
Full Triangulation is only assigned to those Double Matches that overlap with the Base a-b match. The non by-chance people who Triangulate share a common ancestor who passed down the segment to them all.
 
One of the goals of the genetic genealogist is to map the segments of their chromosomes to their various ancestors. The Double Match Groups help delineate these segments and align similarly related people together to give you information that will help you determine the likely ancestor. The DMGROUP is a notation developed by Jim Bartlett that you can use to refer to the segment that defines a DMG.
 
6

A Visual Note

6. A Visual Note
Near the bottom of the map shown above, you see the thick vertical black line that designates the end of the current DMG. This is followed by the start of the next DMG which appears to start one column to the left. You'll see this throughout the Map page.
 
Despite appearances, the following DMG does not overlap with the previous one. If it had overlapped, it would have been part of the same DMG. Its first X is in the same column (Mbp) as the last X of the previous DMG, so the vertical lines must be drawn this way to include the last X of the previous and the first X of the next DMG. If you compare numbers in green in the START-AC, END-AC, START-BC and END-BC columns for these two rows, you'll see that the DMGs don't overlap.