Forensic Anthropology 2011 : 04 : 3D ID Hands-On


[ Music ]>>As we talked about in
lecture, a 3-D ID is based on a subset of standard
landmarks that we used in physical anthropology, that we use in clinical
studies for CT scans, x-rays. And the reason for this is
cause it’s easily translatable from traditional craniometrics
to geometric morphometrics, which is the new
methodology that we’re using. The initial set of
landmarks that we used in this project was 75
landmarks, and we were able to reduce that in a precision
study to 34 landmarks of Type I and Type II landmarks
that we discussed earlier in the lecture. We collect — we have
you collect 34 landmarks, but the ones that you
were actually entering at the time is —
are 32 landmarks. And these landmarks are based
on the standards that — that the left side of the
skeleton is usually recorded. So now we’re going
to the protocol that we record both
left and right sides. But a reference status set
many of the earlier specimens that were collected by myself and some other researchers
only contained the left side of the skull. So if you include
only the 33 landmarks, meaning you omit the upper and
lower borders of the orbit, your reference data set
would be much larger. So the first thing that
we must do in order to correctly identify
those landmarks using a — a stylus with the digitizer
is to mark them with a pencil. Some of the landmarks sometimes
can be a little bit hard to see when you’re trying to go
through the digitizer. So the best thing
to do is just mark with a pencil the 32 landmarks that you will be
including in 3-D ID. And after we have marked
all the cranial landmarks, we will then already — we are then ready to
digitize those landmarks, and register them on the computer before
uploading them into 3-D ID. Now that we have marked the
skull with the landmarks on the skull with a
pencil, we are ready to register those
landmarks, or those x, y, and z coordinates
using the digitizer. You can use the — any
digitizer that’s on the market. The ones that we use is the
Microscribe is what you see here, but they have other
digitizers available, and they will work just
in the same fashion, which will register x,
y, and z coordinates. So the best thing to do is
to register these landmarks in an Excel spreadsheet. And the easiest way is to write
down your list of landmarks in the order that you
see them in 3-D ID, and then you can
just go ahead and — and mark them along the side, and you will get
all 34 landmarks — or 32 landmarks actually
that you will be registering. However, make sure
to leave a space — an empty space for
the right upper and lower orbital landmarks. Because those will keep the
space once you input this into the software. Once you have collected
your data in Excel, one thing that I should mention,
that if you use a Microscribe, you need to use the
compatibility mode of Microsoft Excel to collect
your data, or your x, y, and z coordinates
will not register. So now after you have collected
your data in compatibility mode, it’s — you will have
your landmarks registered on the left-hand side
that you typed in, and then on the right you
will have a list of — of coordinates — your x, y,
and z coordinates on the right. So once you do that,
also go in and erase if you did collect your
right orbital border, because that will reduce your
data set once you import it into 3-D ID. So you can see those highlighted on the Excel spreadsheet
here in red. We just highlight it
to — just to show you. But if you have any missing
values, the one — the — the one great aspect
of 3-D ID is that it does handle
missing values. So if you do have a partial
skeleton, or a partial skull, or a fragmented skull, you can
go ahead and collect that data, and import it into 3-D ID. But however, you
need to make sure that you leave those
spaces blank to be imported. So once you have done that, copy
only your coordinate landmarks, do not copy your
landmark abbreviations. You can then paste them into a
new sheet, and then save them as a tab delimited text file. And you can go ahead
and save that in your — in the same folder that you
have 3-D ID, or on your desktop, or whatever it is
that’s easier to find. And generally what we do is
save them under the case number or name, or test, or whatever
name will make it easier for you to find and — and locate it. Okay. So once your text file
is saved onto your desktop, you can go ahead and
import that into 3-D ID. So then you would call it — for example, in the
case number make sure that you put your number
or your ID on there. [ Silence ]>>And you can process
3-D ID based on determining both
sex and ancestry. Or if you already know
your sex, go ahead and process only
for ancestry only. As when you add the
sex component in there, it will reduce your
correct classifications, as that it’s more
difficult to determine sex across different
populations than it is to actually allocate a known
crania into ancestral group. So once you have
imported that data, you can go into the Options
menu, and select Determine Sex and Ancestry, and also select
the groups that you want to compare that unknown
set of remains to. And you can uncheck the
ones that you don’t want to compare it to, or check
the ones that you want. Or you can choose All
Males or All Females. So once you’re set,
then all you have to do is scroll down
to the bottom. There’s a — a tab
called Process, and you depress a process
tab, and it will provide you with the results
of the analysis. And it gives you a Possier
probability and a typicality. The typicality means
how typical or atypical that unknown skull is to
the reference population that you compared it to. [ Music ]