We are in person at the 2024 Animal Forensic Conference in Gainesville, Florida! Dr. G will be interviewing several of the speakers to give our audience a bit of the knowledge gained through the presentations. We will be releasing each interview individually to allow our listeners to find topics of interest.

What is photogrammetry and how can it help in animal crime investigations? Eileen Roy-Zokan discusses the use of known objects in images to estimate the size of other objects, how this is done now, and where is this technology headed.

We would also like to invite our listeners involved in animal cruelty investigations to visit and join the International Society for Animal Forensic Sciences https://isafs.org/

Mentioned in this episode:

Keep it Humane Podcast Network

The Animal Welfare Junction is part of the Keep It Humane Podcast Network. Visit keepithumane.com/podcastnetwork to find us and our amazing animal welfare podcast partners.

Our next guest is Eileen Roy-Zokan.

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Thank you for being here

and welcome to The Junction.

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It's my pleasure.

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Eileen Roy-Zokan: Thanks for having me on.

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DrG: Can you tell us about your

background and how it relates to

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the field of veterinary forensics?

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Eileen Roy-Zokan: So I have a doctorate in

genetics and I've been working in genetics

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for 20 years, so I mostly do DNA analyses.

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Most of my cases deal with wildlife

versus domestic animals, so I'm usually

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working on poaching cases and um,

species identification, things like that.

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DrG: I just actually, uh,

finished a class on international

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wildlife trafficking and, and law.

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Oh, very cool.

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Yeah.

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So, I was, I was, I was learning so

much about the different laws and,

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And also, like, the things that

people are doing, because it's so

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much complex that I even thought.

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Eileen Roy-Zokan: Right?

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Oh, so much.

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The networks are, are crazy when it

comes to trafficking of wildlife.

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DrG: Yeah, and the excuses they

use and the type of species that

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they take and the reasons for it.

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So, I mean, it is just so complex.

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Eileen Roy-Zokan: It really is.

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DrG: So, what was your topic today?

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Eileen Roy-Zokan: My topic was

something really outside of my field.

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It was on photogrammetry.

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So, um, photogrammetry is the

science of getting information

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about an object or the environment

that's featured in photographs.

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And so my talk was kind

of focused around that.

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DrG: So I love taking pictures

and I love manipulating pictures

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and using things like Photoshop.

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And I was really excited to see

that it's something kind of similar.

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So how does, how does photogrammetry work?

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Eileen Roy-Zokan: Traditionally, in

a normal setting, in a normal crime

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scene, um, you're going to be using,

you're going to be taking a bunch

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of overlaying pictures of your crime

scene, and you can upload it on special

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photogrammetry software, where then it

will recreate, do a three dimensional

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reconstruction of your crime scene.

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Um, They also use this a lot in

archeological digs to kind of map

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out their dig area and also ancient

artifacts that kind of have a

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digital copy of that artifact that

can be safely examined afterwards.

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In my case, I can't do that because

the photographs I'm using are, are.

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Stuff like, um, social media posts

and, um, game camera pictures.

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And with these photogrammetry software,

you need, the camera that you're using

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needs to be known by the program, meaning

you've taken it through a series of

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calibration tests, that the program

then is able to, any of the pictures

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that you take with that camera, is

able to extrapolate the depth of field.

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from each of those photographs

based on the calibration tests.

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And then that's how it's able to

get that geometric information

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from your photographs to build

that three dimensional model.

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When you don't know the camera, like

you're taking a picture off of Facebook,

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that's not possible, so I can't use those

traditional softwares to do my analyses.

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DrG: And I imagine also the

fact that you're dealing usually

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with probably like a single shot

versus multiple shots, that's

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Eileen Roy-Zokan: Absolutely.

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That is absolutely the case.

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Um, I'm usually dealing with just one or

two pictures, um, that I have to compare.

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And there's basically three

different analyses I do.

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One is individual identification.

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I'll get a couple pictures and they're

like, is this deer in this social

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media post the same deer that's

in, on this game camera picture?

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Or I'll get two photographs of like, I had

a photograph of a, of a deer mount that

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was taken in a residence about, you know,

two decades ago versus a deer mount, a

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picture of a deer mount that was taken.

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And another individual's residence

two years ago, it was some

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arguments between neighbors, one

stole something from the other.

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And it's just, is that

the same deer Mount?

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The other thing I'll have is comparing

social media posts or game camera

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pictures to a physical object.

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We have an officer seize,

you know, an antler rack.

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And they have some game camera pictures.

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Is that, did that rack come from

that deer that they have on the game

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camera or the social media posts?

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DrG: One of the examples that you

posted was as far as like doing,

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taking measurements of a deer antler.

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And that was, if I understand

it correctly, to see if it was

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like poached the correct time

or, or taken at the correct time.

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Eileen Roy-Zokan: Yeah.

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So here in the state of Florida,

we have a regulation that, uh,

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male deer cannot be taken if their

antlers are less than five inches.

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So there was a social media post of an

immature buck that the person that posted

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the social media post, um, they actually

strapped on an eight point rack on On

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the, on the immature buck using a towel to

make it look bigger than it actually was.

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Um, and our officer seized the

rack and they had two questions.

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Whether the rack they seized

was actually the antler rack

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that's featured in the picture.

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And then in the picture you

could also see the actual antler

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point of the immature buck.

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Could I somehow get an estimate of the

size and length of that antler point?

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And because, um, What I have to use is

either a program like Photoshop or another

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free version of Photoshop known as GIMP.

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to try and get the number of

pixels along these objects.

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I so you need an object of known

size in the same plane as the object

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you're interested in measuring.

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And so in this picture, I saw that one

of the antler points on the rack that was

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used as a toupee was right next to that.

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actual antler point of the immature buck.

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And so I used the rack that I had

in the lab, um, that was seized.

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That was the actual rack

in the used as a toupee.

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Um, I measured that out as about 2.

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6 inches.

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And then I was able to then look

at the, I got the number of pixels.

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Um, so I measured out, the length on GIMP

and got the number of pixels that was

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contained along that particular antler

point on the toupee rack and then I got

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the number of pixels of the actual antler

point on the immature buck and then

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from there what I do is I know the size

of the antler point from the physical

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rack I have in the lab it was about 2.

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6 inches.

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And so what I'm able to do is say, okay,

this number of pixels for that particular

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antler point divided by its actual size

is this number of pixels per inches.

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So how can you use that as a

conversion factor, because you know

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your number of pixels per inch.

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And then from there, I was able to measure

the number of pixels along the antler

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point on the immature buck, divide that by

the conversion factor, that's your number

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of pixels per inch, and that will convert

that to, will give you the size estimate

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for the object you're interested in.

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Now this hasn't been court validated.

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We are testing it in the lab to get

the statistics and variations behind

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these kinds of estimates, but that's

kind of the approach that I use.

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DrG: So this is a relatively

early field, right?

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So there's still a lot.

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So where do you see this going

as we move forward in forensics?

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Eileen Roy-Zokan: Oh boy.

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It would be really great if we can

kind of automize this a little bit.

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Um, we also need to test

out different programs.

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I know there was a dissertation recently

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they, Did these kind of analyses, but

they use the Pharaoh scanner as well

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and Photoshop and Gimp and compared all

three methods and although their sample

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sizes were low, it's very promising.

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So there's so much technology development

that can happen, but if they could get

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that more automized and the statistical

variations down, so it's going to take a

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lot of testing of different environmental

factors, different angles and things

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like that to get that more up to date.

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DrG: Right, well I'm looking forward

to seeing where this takes us because I

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think that there's a lot of information

with how many people take pictures

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of everything and so many sources.

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I think that this is going to be really

useful and relevant in crime scene

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investigations, especially with animal

crime scenes and as you mentioned with

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like wildlife, uh, illegal wildlife trade.

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Absolutely.

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Yeah.

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Yeah.

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So, thank you so much for being here

and thank you for talking to us and

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thank you for what you're doing.

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Eileen Roy-Zokan: It was

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my pleasure.