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Completely modeling an excavation with Photogrammetry - Ep 194
1k Plays2 years ago
We start today's show with a discussion about the current uses to Twitter and Mastodon after Elon Musk's takeover. For the last two segments, however, we talk about a novel way photogrammetry is being used on an excavation in Bulgaria. Want to see the excavation at any level? This will do it!
Transcripts
For rough transcripts of this episode go to https://www.archpodnet.com/archaeotech/194
Links
- A Photogrammetry-Assisted Methodology for the Documentation of Complex Stratigraphic Relationships
- Blender
- The Harris Matrix w/ Edward Harris Himself - The Archaeology Show Ep 13
Contact
- Chris Webster
Twitter: @archeowebby
Email: chris@archaeologypodcastnetwork.com - Paul Zimmerman
Twitter: @lugal
Email: paul@lugal.com
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Transcript
00:00:01
Speaker
You're listening to the Archaeology Podcast Network.
Episode Introduction
00:00:08
Speaker
Hello and welcome to the Archaeotech Podcast, episode 194. I'm your host, Chris Webster, with my co-host, Paul Zimmerman.
Episode Preview
00:00:15
Speaker
Today we start with a discussion about social media and how we're using it these days. But for the rest of the show, we talk about a great way photogrammetry is being used from a recent paper. Let's get to it.
00:00:26
Speaker
Welcome to the show, everyone. Paul, how's it going?
Paul's Recent Projects and Twitter Frustrations
00:00:29
Speaker
It's going pretty good, actually. I still own Unemployed, but that means that I've been getting a lot of time to do things around the house after being gone half of last year.
00:00:41
Speaker
I've had all sorts of different projects, things that I wasn't able to work on that have been percolating. And so I've just been on this great creative streak. The software, the Total Station software that I've been working on forever is in great shape and it's up
QGIS Plugin Success and ArcGIS Challenges
00:00:57
Speaker
on GitHub. And I'm trying to figure out how to publicize it because I've been off of Twitter for the last few weeks because I got so fed up with it. And that would normally be my go-to.
00:01:08
Speaker
But, you know, I've had time and not doom scrolling to do other things. And it's been good. I mean, just the weirdest little things. Like I had an exporter for the data that worked great with QGIS and I had a note to myself to test it with ArcGIS. I couldn't do that in the field because I didn't have ArcGIS on my computer in the field, but I've got it on an extra computer I've got here at home.
00:01:34
Speaker
So I tried it and it didn't work, no surprise. And then just kind of Googling something randomly, I found that there was a Python package for creating shapefiles. I was like, oh, that's interesting. I looked at it. It was easy, converted that whole exporter from exporting CSV to shapefiles. Now it works with my QGIS and it works with ArcGIS. And then I'm like, well, you know, now that I've got it working so beautifully with QGIS, I spent a couple days and built a QGIS plugin to
00:02:01
Speaker
to do the imports from the exported data and it's just all kind of coming together like that. I'm sitting here working on a little sensor that I'm going to build modules of for Raspberry Pi Pico with a temperature and barometric pressure sensor and maybe I might integrate that into my software too. Just exploring lots of little things.
00:02:24
Speaker
Wow, it's been a lot of fun. Yeah. Let me ask you about Twitter real quick.
Twitter Usage and Content Curation
00:02:28
Speaker
Well, let me ask you about Twitter real quick because you're, you're, you use Twitter a lot more than I do. I don't know if you'd consider yourself a power user, but you definitely use it a lot more than I do. It was a while back, but when I was more heavily into Twitter,
00:02:41
Speaker
I had all these lists and groups and what do you call them? Group not groups, but I guess lists. And then I used an app, was it Hootsuite or something like that, where you can have just different columns and you can have those filtered to a hashtag or filtered to a list of people that you follow or something like that.
00:02:59
Speaker
And I never, I almost never like just went to like regular, just Twitter, you know, whatever, whatever's on there and just a scrolled random stuff. So all these people saying, you know, Oh, Twitter's gotten all crazy and it's, you know, it's all conservative and the, the racism has gone up and all this has gone up. But like, if you don't follow those people and they're not in your lists, how would you ever even see any of that stuff? You know what I mean? Like you curate your own content. If you want to, do you use Twitter in that way? Are you seeing all this other crazy stuff? That's, you know,
00:03:29
Speaker
I wasn't using the way that you're talking about. Basically, I followed a bunch of people, a couple thousand maybe, and I had about 1,500 followers. Things would just show up on my feed, and if it looked interesting, I'd get involved in it. It might be a political discussion more often than not, or lately it would be an archaeological discussion. But then I also get direct messages from a lot of people because I've got them open.
00:03:54
Speaker
So, you know, I'll have archaeology students ask me questions on it and I take time to actually try to answer as best as I can, you know, what they're asking.
Networking on Twitter and Challenges
00:04:06
Speaker
So, you know, I've expanded my network of people I interact with quite a bit with that. And a lot of people who are a lot younger than me, which is interesting because it opens my eyes.
00:04:20
Speaker
to maybe keep my brain a little bit more limber, but it opens my eyes to ways that maybe I wasn't raised to think but that are interesting nonetheless. All that said, yeah, I started seeing an uptick of bots and some really just vile conservative stuff that I can't go along with.
00:04:38
Speaker
And my DMs were getting pummeled, absolutely pummeled with bot accounts. And it stopped being about the conversations I was having. And the conversations all started being conversations about Twitter.
00:04:53
Speaker
And that was not interesting to me. I mean, I thought that was kind of fun to watch the train wreck of it, but it wasn't improving my life in any meaningful way. So I was like, you know what? Let me just take a break from this. And that's been a few weeks and I haven't missed it with the exception of
00:05:12
Speaker
I've lost certain connections. Like I said, I've been on this creative streak and that's in large part, I think, facilitated by not wasting time on that social media platform. But I don't have a good way of telling people about it. I mean, I'm telling you about it and telling our listeners about it right now. And hopefully I get some engagement that way.
00:05:31
Speaker
But my typical way of announcing something that interests me and getting responses to it would have been on Twitter. And we use that to great effect in the field this last season. But I've now cut that off for myself.
00:05:48
Speaker
So yeah, so I just I got fed up with it. It just wasn't fun anymore. And I'd already noticed that I initially started using it because I was getting all sorts of information about the Yemeni war from people living in Yemen.
00:06:03
Speaker
And one by one, those people dropped off. I don't know if they died, if they went to jail, if they got set up with it. I have no idea what happened. And now I hardly ever get any Yemen news. And I get some political stuff and I get a lot of cultural stuff around archaeology.
00:06:24
Speaker
in its broadest sense, and that's been great. But at the moment, I can't deal with all the other garbage. And I've looked at other
Mastodon vs Twitter: Community Dynamics
00:06:33
Speaker
things. A lot of people moved over to Mastodon, and I set up a Mastodon account on the archaeo.social
00:06:40
Speaker
federated, whatever it's called. It misses for me what I really liked about Twitter, which was that fire hose of different people and ideas and things that are going to get me upset. If I go to the Mastodon pages, it's a bunch of people that I'm friendly with and basically agree with. It doesn't challenge you.
00:07:05
Speaker
Yeah, it doesn't challenge me, but it also, I don't mean that like in an intellectual sense. I mean, it doesn't stimulate me in the same sort of way. If I want to have an archaeological discussion, that's wonderful, but that's not the only reason why I was going to Twitter. I was doing that for archaeology. But like I said, with those students direct messaging me, more often than not, the really interesting discussions would happen not with another archaeologist, but somebody that was interested in archaeology.
00:07:32
Speaker
And they're not necessarily going to be on that Macedon server. Right.
00:07:36
Speaker
Okay.
Value of Slack for Archaeological Discussions
00:07:37
Speaker
Well, I will tell you one place that, uh, another thing I want to bring up before we get to the, the article for the day is, and this is only because I've seen you guys having a really good discussion in the last little bit here, last couple of days, but over on our members Slack team, if you're not a member, go over to our podnet.com forward slash members, one of the, I would say primary benefits that you get. And it's one of these benefits that just gets better and better the more people get on involved with it. And the.
00:08:04
Speaker
Archeotech channel over there for our members slack team. We got a couple of people over there like to really say a lot of things, especially one of the people who's been a former guest here, water Yuperman, and he's over in Belgium. He's an archeologist and you guys were having a discussion about one of our last episodes. You care to discuss anything that you guys talked about?
00:08:24
Speaker
Yeah, so he commented that he liked Marco, Marco Wolf, who was the last person I interviewed on this podcast, he liked Marco saying, no, he doesn't see himself as a digital archaeologist. And this, you know, that's fine. I started out that episode talking about how we are really calling into question the utility of the term digital archaeology.
00:08:47
Speaker
But that said, Marco, you, me, a lot of people that we've interviewed on this podcast, Walter himself, are people who are very comfortable with digital techniques to the point sometimes that we're uncomfortable with non-digital techniques. Walter thought that that was an interesting response from Marco.
00:09:11
Speaker
Yeah. But then more so, I asked Marco toward the end, because Marco also does CRM work, well, the equivalent of CRM work in Germany, and asked him if he's allowed to use the various digital techniques he's most comfortable with, or if it's ruled and regulated to such a capacity that
00:09:32
Speaker
He can't do that. He has to do things on paper or he has to do things in certain regulated ways. Wouter then was expressing his own experience doing something very similar in Flanders.
00:09:48
Speaker
And, you know, it's just those perspectives like that. And that's something, you see, maybe that's part of why I don't feel the need to move over to Macedon because I have conversations like that with other archaeologists on this podcast and on the Slack channel and on some discords that I'm on and some various other places where it's, you know, like minds with different perspectives.
00:10:13
Speaker
which is definitely valuable, and it's definitely fun. But yeah, so Walter contributes all the time and always has good and insightful things to say based off of his own experiences. And so he had the commentary on that recent interview with Marco, and that was interesting to see.
00:10:33
Speaker
how different people attack the same sorts of problems or how they're not necessarily encountering them in the field. Like, as I said in that thread, how I'm not really encountering a whole lot about rules and regulations about how I conduct my field work when I'm working in the Middle East. They just don't exist. There are expectations as an academic, there are expectations to the Department of Antiquities in the various countries of what I have to do, but it's not regulated in the same way that CRM is in this country.
00:11:03
Speaker
Okay. Well, like I said, a lot of interesting discussions happen over here. We need more people to not only engage the ones that we have that are members, but also we'd love to have more members, if not just to have these kinds of discussions in a, basically it's really a closed forum, right? I wouldn't say it's private. We don't say anything in here is like sacred, but it's kind of understood it is a little bit because it's a little bit of a private club.
00:11:27
Speaker
But, and you have to be invited over here to, you know, to participate. So in that respect, it kind of is. But, you know, we really, what we really need is a moderator. So I'll just put a little bit of a plea out in segment one here, hoping, hoping more people hear it than not. If you find yourself in having two different characteristics, one, you're a relatively social person conversing with social media and, you know, being online and those sorts of things, and you don't mind that. And two, you listen to all, if not most of the podcasts on the APN.
00:11:57
Speaker
in real time as they come out. That's a tall order, but we have tens of thousands of people that are listening to this show right now on the All Shows feed. I know that that feed gets 25,000 to 40,000 downloads a month. There are a lot of people over there that are listening on that feed. If you're listening on that feed, that means you're hearing everything as it comes out. If you're one of those people that
00:12:21
Speaker
are listening to it in near real time, we would love a volunteer in that Slack channel to get a free APN account and go over there and help stimulate conversation. Just, you know, listen to the episode like anybody else would and ask some questions in the channels and see if we can get people to start these conversations because some people are just finger shy and they don't want to go in there and type, but they're more than happy to comment if they see something coming in. So we need people to go in and do that. I would love to be that person and have that be my thing, but
00:12:48
Speaker
I'm just stuck editing all the time, so as soon as I'm done doing that and I can get somebody else to edit, that's the first paid job at the APN. I've said that a million times, but if I can ever get that off my plate, then I want to be more engaged in all these other ways, but it just can't happen unless we have the content. We don't have the content unless I get this stuff edited.
00:13:08
Speaker
All right, well with that, I think let's just go ahead and take a break. This was the social media segment and we'll get into the article in the next two segments and see what we can learn about photogrammetry and the way these authors are using it. It's pretty cool. Stay tuned for that. We'll be back in a minute.
00:13:24
Speaker
Welcome back to episode 194 of the archaeotech podcast. And we're going to talk about an article that was in
Introduction to Photogrammetry Article
00:13:30
Speaker
the November 2022 issue of Advances in Archaeological Practice. If you don't have access to that, it's through your SAA membership. If you're not an SAA member, well.
00:13:40
Speaker
I would say head over to the link in the show notes and it's on Cambridge University Press. That's where the essay holds all their articles from an official standpoint. You could buy it if you want to, but you can also contact one of the authors by clicking on their name. They usually have email contact or just search for their name and their institution online and you can find it. And they'll more than likely be happy to send you.
00:14:00
Speaker
an article, as we mentioned in the last episode. The authors for the article, which is titled, a photogrammetry assisted methodology for the documentation of complex stratigraphic relationships. They're always a mouthful. The authors are Brent Whitford, Karen, well, I'm going to get all these wrong to you, by the way. Karen, I should have you do it. You came in. Let me do it. Let me try it. You know what? You do it because these are more in your wheelhouse. No, no, no. We'll get on you now. All right. All right. So, well, Brent Whitford, I've got Brent's name.
00:14:30
Speaker
Um, and then came in boy, a Jeff boy, a Jeff, um, Miroslav Ivanov, constant in, Oh man, two, two fact, Jeff and Yavor boy, a Jeff. Oh, I wonder if they're related to two people at the same last name. I don't know if that's a common last name or if it's the same last name relation, but.
00:14:53
Speaker
Anyway, Paul, I didn't have access to this article because I had to renew my essay membership. I have read it since you sent it to me about 40 minutes ago. And I read your notes. But why don't you give us a brief and get us started on this. Right. So this one, I love mining AAP for content.
00:15:10
Speaker
And every issue that comes out, you know, half the titles, the article titles in it look interesting to me. And this one immediately looked interesting to me. It looked interesting to me specifically because in the last few episodes of the podcast and talking with Marco, photogrammetry has been coming up a lot.
00:15:29
Speaker
It's turned the corner from a few years ago, we did an episode on Structure from Motion. To me, it was very novel at the time. The documentation about how one did it at the time in the article that we were reviewing back then made it seem like a fairly bespoke
00:15:48
Speaker
sort of approach, not something you would just do as a matter of course. And starting last spring, when at Lagash, the field director, Sara Pizzimenti, just brought along her DJI mini drone and
00:16:06
Speaker
would just fly it and do photogrammetric models every day of her trench, casually, just because that's why not, I can do that. Really opened my eyes too. I can't be mystifying this. And this goes also to the question of, does digital really mean much anymore in archaeology? Because this just a few years ago was a very special tool and now
00:16:32
Speaker
It's useful to the point of people aren't thinking about it too much, they're just doing it. But for me, one of the big issues I've had, even though I've seen some really great work done with photogrammetry, is can we use it to reconstruct the volume of the soils that we're moving, of the features and contacts and so on.
00:16:58
Speaker
The answer is yes, I know we can, but I hadn't seen anybody actually doing that with my own eyes. I mean, I should have talked to Marco about it because I think that that's something he's been doing. And I wondered how one would approach it. And so the title of this article made me immediately think, OK, this is maybe going to tell me how to do it. Unfortunately, it paid off. It does tell me how they did it. It tells me like these AAP articles often do in a lot of detail with this software and that menu item and
Praise for Photogrammetry in Archaeology
00:17:27
Speaker
so on.
00:17:27
Speaker
which for me isn't the most interesting thing. I don't think it's particularly useful. For some people it is, but I want to see just the general process. And let me back out a little here. I love cooking. I cook all the time. I never cook from recipes, but if I'm trying to cook something new, I'll kind of half use the recipe until I grok what they're trying to do and then stop using the recipe and just do it myself.
00:17:54
Speaker
So a lot of the AAP articles are recipes, but because they're software based and because software changes all the time, I don't know how long live those recipes are going to be. They might be expired a year from now. But well written, well argued, the underlying ideas behind it
00:18:16
Speaker
go between a recipe telling you to chop up half an onion and this much celery and that many carrots, this size, saute them in olive oil for this long until they're tender or whatever, versus a recipe that says, yeah, make a mirepoix.
00:18:34
Speaker
Both of those are valid ways, but the important thing is to know how to make a mere plot. And this article gives you the step-by-step for a few of the things, but mostly it's about making that mere plot.
00:18:47
Speaker
The other thing that really caught my eye about the title, and I haven't gotten past the title yet, is the documentation of complex stratigraphic relationships. I thought, okay, complex stratigraphic relationships, that's it because I could figure out a process for doing this with
00:19:07
Speaker
big things with walls and whatnot. All the sites would really matter. It would be complex stratigraphic relationships. Knowing from sites I've worked on, yeah, I've worked on some of those sites. Then flipping through as one does before actually digging into the article, wow, they're figure four. They show
00:19:31
Speaker
And Complex doesn't even come close. I mean, I look at the, they've got an overhead shot North of Mosaic and also a color illustration of that same level. And that color illustration positively makes me itch.
00:19:48
Speaker
There are so many like post holes and pits and different layers and things going on all at once. It's amazing the detail that they're doing. It looks like a Jackson Pollock painting. It really does. It's just a splatter all over, except for with that face right in the middle. The guy with the flat black cap. Oh, I can see it. I pulled that out too.
00:20:14
Speaker
So, seeing that, I thought, okay, well, you know what? I believe them when they say complex stratigraphic relations. That is very complex and clearly they care about reproducing it. So, that's why I decided, you know, hey, maybe I might learn how to make that mirepoix and maybe I'll learn about it from people who clearly are better cooks than I am. So, that's why I dug into it.
00:20:43
Speaker
Okay. Well, just to set the stage of what we're talking about here, this is from a site called Tell Unit Site. Am I saying that right? Do you think Unit Site? I don't know if it's Unit Site. I looked at it online
Archaeological Work at Tell Unit Site
00:20:55
Speaker
on Wikipedia. It's got a bunch of different names. Unit Site. I'm not sure how it's pronounced because I don't know Bulgarian.
00:21:02
Speaker
Yeah. I don't know either. Is that E on the end like pronounced, or is it just like site? Like we would say, I doubt it's like what we would say in English, but anyway, uh, it's, it's in Bulgaria. Uh, it's been excavated since 2000. Uh, well they've been excavating it since 2013 and the first excavations over 1939, right? Yeah. That's what they said. Yeah. Let's see. Yeah. It says they have levels dating from the Neolithic through the medieval periods with some gaps in between. So there's just, there's a lot of use that's been on this site throughout time. And that's not,
00:21:32
Speaker
I would say uncommon, especially for that area. We've seen sites like that all the time in the United States as well, where you've got just a complex relationship, especially along waterways or resources or something like that, where you're just going to have centuries and centuries and centuries of reoccupation and use by maybe the same people, probably different people, who knows, but different technologies and things through time. Documenting that and visualizing it is a complex task.
00:22:00
Speaker
Now, the site itself, they said tell. I was like, there are tell sites in that part of the world, but when you see the aerial imagery of it and the reconstructed DTM of it, yeah, it's a tell site. And that being that people have gone to that same spot of land repeatedly over the millennia and done their stuff. And as people do things, they accumulate trash where they live and structures and everything else.
00:22:25
Speaker
And so it's layered up, you know, occupation upon occupation, activity upon activity, to form a human-made hill, and that's what a tell is, and that's what this site is. Their interest, well, so I think it must be from the 1939 excavations, that hill is very round, and it's bisected.
00:22:45
Speaker
right down the middle and half of that top has been cleared off. And then you can see in the photos a bunch of five by five trenches, which must be theirs. So I'm guessing that those earlier excavations back in the era of big digs,
00:23:00
Speaker
dug away that whole top half. But where they're starting from is early to late Calcolith. Well, they're starting from late Calcolith going down to early Calcolithic levels. And I think they said something like 11 different levels there that they've been in so far. And it looks like they still have a few more meters to go
00:23:18
Speaker
in the site before they hit the level of the plane. So it's a substantial site. And again, the complex stratigraphic relations, it looks like they're trying to dig it very carefully, very stratigraphically with really complete documentation. And it's that complete documentation that allows them then to do what the meat of this article is, the photogrammetry.
00:23:42
Speaker
It's interesting to me with the figure two shows that you can see that bisecting of the tell site and then it shows the models that they built around that from what it originally would have looked like and then what it looks like now as well. And it's impressive to me the discipline that has been shown here for the last 80 years to not dig that other half.
00:24:05
Speaker
honest with you, right? Like how often do you see that where it's like bisected right down the middle and they just continue excavating over here, probably with the thought that it's much the same on the other side. I would assume unless there's something really special over there, but I guess one of the chances of that, I don't know much about tell sites and what this could be, you know, could that be something like they haven't found the thing that a tell site would have in this area. I don't really know, but, um, to not dig that over there provides a nice little preservation example and, and just a cross section right down the middle.
00:24:35
Speaker
Yeah, just sliced. It's not a sight to behold. Yeah, for sure. Yeah, they say here that the dating of the sites in this period in the early to late Calcolithic is not clear. And they do say that that's probably related to the need for better radiocarbon calibration curves for the region. So dating is an issue, one of the issues that they're working with here.
00:24:59
Speaker
And they say that the method they've come up with will allow for better stratigraphic documentation and help address the, you know, better stratigraphic documentation.
Improving Stratigraphic Documentation with Photogrammetry
00:25:09
Speaker
Basically, they're hoping we'll start addressing some of the dating issues that are in the site and in the surrounding sites. So that's why they're using this technique to try to do that a little better. Yeah. So it's a bit of a call to arms too. It's like, hey, look at how well we can document this incredibly complex site.
00:25:25
Speaker
If we teach other people how to do the same, then maybe we can start having the same conversation. So they raise this as one of the points early on in the article, but then they don't actually dig into that. The rest of it becomes more and more technical about what they did and why they did.
00:25:42
Speaker
So, to cut to the chase here, essentially what their method does, it allows them to create section drawings anywhere across a trench without having to leave balks.
Creating Section Drawings with Photogrammetry
00:25:53
Speaker
So, normally, you dig your five by five, your 10 by 10, your two by two, whatever it is, and you have the balk as a witness for the strata that you didn't notice as you're digging down, or I didn't notice.
00:26:06
Speaker
No one to do. What's that layer doing over there? Oh, shit. Oh, oh, yeah. Oh, I thought it seemed a little darker there. But yeah, when you see it in the section, holy cow, that's a fire pit. Yeah, I'm a terrible digger. I admit it. I love it. But I can't do it unsupervised. I need somebody better than me. Otherwise, back to the food analogy, I'm going to burn it.
00:26:31
Speaker
Indeed. Yeah. You know, the crazy thing about these books, I see these when we read articles from really, you know, Europe to Middle East, these regions over here, Eastern Europe. You see it all over there, but I have almost I can't think of a single time when I've excavated in that way.
00:26:49
Speaker
in the United States. And I've done a lot of excavation in Nevada, and I've did a lot of excavation down in the Southeast and a little bit up in the Northeast United States. And we just opened up another unit and just kept on digging. If it was a one by one and a block excavation, we just kept on doing it. Now,
00:27:07
Speaker
We usually did it in 10 centimeter levels. So every 10 centimeters, we would have a floor plan on our notes. So there's that and those could probably be reconstructed for some sort of sort of rough 3d model, you know, a low resolution 3d model. But aside from that,
00:27:24
Speaker
we did not record those those bulks. So I think a photogrammetric method would be good for something like digging where I've done because if you're if you're taking images periodically as you're going down and creating those layers then you can do a lot with that later on.
00:27:39
Speaker
Yeah. I mean, it requires the discipline, which again is something that they seem to have on this. The traditional way of leaving lots of balks is called the Wheeler-Kenyon box grid. It looks almost like, even though the disparaging of it in the article, it looks almost like that's what they're doing here. These are five by five units, but they all have very defined balks around them.
00:28:05
Speaker
And that's actually not a way I've tended to excavate myself on the projects, but I think that's because most of the projects I've worked on have been in the Middle East and they've been architecture focused. And so once you hit walls and such, depending on the strategy, oftentimes you'll follow those architectural spaces instead of your arbitrary, you know, north, south, east, west.
00:28:26
Speaker
grid, but that varies project to project. Anyhow, the dependency on leaving the box then for the Wheeler Canyon box grid system means that you cut up your site in ways that make it hard sometimes to connect from one end to another or from one trench to another, from one unit to another. To deal with that, another thing that they also throw away is the Harris matrix.
00:28:51
Speaker
I don't care for the Harris Matrix myself. I understand why people find it useful and I understand why it's in the workflow of so many projects.
00:29:00
Speaker
But they hit, for me, the nail right on the head as to why they say, and I'm just going to quote straight out of it, says, an additional method, the Harris Matrix, although useful, is merely a representation of stratigraphic relationships in 2D diagram form that provides no visual facsimility of the field from which to make further assessments, interpretation, or corrections.
00:29:23
Speaker
For me, it's that transposing of the layers from this organic sense of what's interrelated with everything else to a very sterile grid system for 2D representation. For me, I lose a lot there. It's like going between tasting the food and just reading the ingredients list.
00:29:47
Speaker
Right. Yeah. I hear you. Well, I think with that, we will take a break and just incidentally, and I'll leave this in the show notes, but back at the, what was it? The 2017 SAAs in Vancouver, Canada. I interviewed Edward Harris, the inventor of the Harris matrix. Yeah. On the archeology show episode 13. I knew I did it. I had to look it up on the APN while you were mentioning that.
00:30:10
Speaker
And I'll drop that link in the show notes because it was really, it was a really interesting one. That was a great episode. And I remember it and I listened to it and I was like, afterwards I'm like, okay, I got to give this another try. And I went and I tried to give it another try and I came away. Still hated. Yeah, still not for me. Well, I'm not hated because I don't think it's a bad thing. I think it's a very good thing and very useful, but it just does not work the way my brain works.
00:30:37
Speaker
Yeah, yeah, there's never really used it either
00:30:41
Speaker
So once they mentioned that, I was all in on the article because at that point, they'd hit all the things, the complex stratigraphic relationships, the photogrammetry, hey, we've got a way of doing it. Hey, if you use our method, we can have a conversation. Oh, and there are these other things that might potentially be useful, but we don't think so for these reasons. And so I was all in at that point. Nice, nice. All right. Well, let's go ahead and take a break and come back and wrap this article up back in a minute.
00:31:11
Speaker
Welcome back to the Archeotech podcast, episode 194. And we are talking about photogrammetry being used in a, I wouldn't say a new way, but definitely more robust way than we've probably seen in the past, at least in the journal articles that we've read. So Paul, let's get to the meat of this. You really dove into some of their data and methods and things like that. What are they doing?
00:31:32
Speaker
Okay, well, the meat of it, you're getting hungry too. I'm absolutely hungry. Dinner's right around the corner. Yeah, I'm starved. Okay, so basically they start out with a DTM of the site and from that they create a solid 3D model.
Digital Terrain Models in Excavation
00:31:47
Speaker
So it's not just the surface, but it's also extruded downward, some arbitrary depth, so it goes down deeper than the surrounding field. I'm not entirely sure why they start with this, actually, because it doesn't
00:31:59
Speaker
reflect anything else or it's not obviously reflected in any other part of the article. I think though it's so they can have a baseline that they can then
00:32:10
Speaker
essentially re-excavate the units that they're digging. And then they can use that for comparisons between various trenches, between the different excavation units. They're excavating in a 5x5-meter grid, like I said before, with bulks between them. So it's almost the Wheeler-Kenyon box. And then every time, they're excavating very slowly and stratigraphically. So they're not doing arbitrary depths, though I think you could adapt this
00:32:40
Speaker
this system to an excavation strategy that uses arbitrary depths, but they're really relying on the skill of their excavators to recognize the strata in the various contexts as they're going down. This is tough and kudos to them for being able to do that. Again, that figure showing the complexity of all the contexts just in one layer is phenomenal.
00:33:04
Speaker
I have excavated stratographically before, but it was nothing this complex, right? Like we used, we did that in the Southeast where there were, you go down a meter and a half and there's three strats, right? And it's all sand.
00:33:15
Speaker
You know, not that big of a deal, to be honest. Yeah, we excavate something like this at Lagash and with great results now that everybody's kind of getting the hang of it. And again, this is, I mentioned earlier, with Sarapisiminti, this is the way that she insists that the trenches that are under her
00:33:39
Speaker
field directorship, I don't know what they're under, or overview, our dog. And it's really quite a skill, and it's a skill that I personally don't have, but to watch people that can do it, and the kinds of detail that they can pull out is amazing. So starting with that, once they get to a new stratum, they overlay a one by one meter string grid to help with the photography and the illustration.
Using Blender for 3D Models
00:34:06
Speaker
And this is something I believe
00:34:07
Speaker
in the way they talk about it. This is something that they've been doing for a long time that they did it from before they were doing photogrammetry on this project. And that's something that we've seen before on other, you know, I've worked with string grids either, you know, nail them in, you know, into the box and draw them across or even sometimes where you have a frame with the strings across it. Yeah. Right.
00:34:30
Speaker
Yeah. So that's something that people have been using for decades. Anyhow, because of the method that they're doing, they're still doing that. And so they dig in their five by fives when they get to a new stratum, they overlay the string grid, they do all these photographs. Now they do extra photographs because they want to turn
00:34:48
Speaker
photogrammetry, they still do the illustration. You know me, I'm big on people still illustrating. But now they've got that grid that they can use for aligning and scaling their SFM, their structure for motion photogrammetry models. So they kind of stumbled into ground control points, into GCPs with this grid, which is, I think, brilliant and fortuitous and cool in so many levels.
00:35:18
Speaker
So they're using that and they're using, I think they said they were using Metashape. They go into a lot of detail about the settings and about the 2.5D and the sparse point cloud and all that stuff that frankly, I don't care about.
00:35:33
Speaker
Yeah. I don't think it's useful because there's so many different ways of getting very good photogrammetric models now. It might've been useful a few years ago. It almost certainly was important and useful when they started the project. Right. But right now, it doesn't do much for me.
00:35:49
Speaker
Anyhow, they get that model and then they move into Blender of all places. Now, Blender is typically conceived of as a 3D modeling and an animation program, but it's open source. It's extremely powerful. It's deep. It's hard to kind of get your brain around initially. And once it clicks, people love it. So it's interesting to me and I think good.
00:36:15
Speaker
in their whole workflow, that that's where they're doing the majority of their work. In fact, they have a digression about doing some work that they're trying to do in ArcGIS because, you know, hey, it's in GIS and it's going to be better that way.
00:36:27
Speaker
and all gooder all the time. And it turns out that they've run into all sorts of problems with it. It doesn't render, things crash, things don't work. So they go back to Blender, where they can do it pretty easily. And again, back to the thing about all the details. They do explain all the little details of how they do things in Blender. In this case, I think it's more important, though, because this is where you start to understand, I start to understand,
00:36:53
Speaker
how they are turning these photogrammetric models into a real 3D space of all these contexts interlocking, as if you were to take a chunk of soil out and have it. And that's something that you and I have discussed a lot in the past about having documentation that could permit somebody in the future to reinterpret. My master's paper was on reinterpreting
00:37:20
Speaker
some of Woolley's excavations at the Royal Cemetery of Orr. But when we talk about archaeology as a science, one of the big things of science is reproducibility, which we don't have if you're excavating, right? You can't re-excavate something. We teach, you know, Archaeology 101 students that right away is that, yeah, you'll never be able to re-excavate. So what do you have to do? You have to document really well. What they're doing here is documenting really well very organic shapes.
00:37:47
Speaker
that have a chronology inherent to them and have human activities inherent to that chronology. And they're capturing that. And so, anyhow, they get each level modeled and then they extrude it downwards so that it would intersect the next lower level.
Innovative Photogrammetric Analysis Methods
00:38:05
Speaker
It doesn't have, it can be any arbitrary depth. It just has to be deep enough to hit the next level down. Which is cool. That's the part I think is really neat because I haven't heard people talking about really doing that before.
00:38:16
Speaker
Right. No. And then it gets even smarter. They're doing it in Blender. So then they take that photometric model from the next level down and they slice the bottom side of that top model with the next lower level down. And they keep on doing that. I think they said they had some like 80 different models, units. Yeah. Oh, no. Models. I can't recall.
00:38:37
Speaker
of these things, but then it gets more complex. Because that'd be fine if you just had a simple stratum that went from one bulk to the other bulk, north, south, east, west, and maybe it's a little bumpy or a little sloped or whatever. And then you've got another stratum directly underneath. But what they have are, like I said earlier, tons of little pits and post holes and use areas and all sorts of stuff. I'm not sure exactly how they're defining their strata,
00:39:02
Speaker
because I can't quite see it in their illustrations, doesn't matter. At this point, I trust what they're doing. But then to get all those little context, what they do is they remember I said they were doing illustrations.
00:39:20
Speaker
They make shapefiles of those illustrations scaled and everything in GIS. They import those shapefiles with a plugin that I didn't know existed for importing shapefiles into Blender, another open source project and they've got it linked in the article. They import those shapefiles and then they slice those contexts out of the solids that they just made in Blender with those shapefiles.
00:39:44
Speaker
And they call it like a cookie cutter, which was funny because when I was reading, I was like, oh, that's kind of like a cookie cutter. And then they say cookie cutter. Here we are in food again. Dammit. So one thing that's unclear to me is that these shapes are organic. And if you have a cookie cutter, you would end up with kind of cylindrical shapes.
00:40:07
Speaker
or straight walled, and that's not what they show in their final result. Everywhere else, they talk in lots of detail about how they do it, and here they kind of gloss over it. Something about voxels and smoothing, but I don't know how you don't end up with either cylinders or something that looks like wedding cakes or upside-down wedding cakes. You'd be familiar with this, Chris, like you see of
00:40:33
Speaker
airspace, right? Yeah. Yeah, for sure. The upside down wedding cake model of different classes of airspace. I don't know how they get from that to something that's nice and smooth that shows like the roundness of a pit. I mean, it sounds like there's a lot of interpolation going on as well, you know, when they create these models. And I guess it really just depends on, you know, they're digging stratigraphically, but
00:40:55
Speaker
When you're coming down and you encounter some soil change, right? You encounter something different and then you start digging down around it. Maybe you leave that for a little while and then, you know, then you go into it, or maybe they're, they're excavating it, everything down uniformly, but then mapping as they go. But the, as they go part is the one that will determine that shape, right? Because what is, when do they stop and measure? That's what will tell determine the shape.
00:41:21
Speaker
Yeah, so I do think, looking again at that figure four, the ortho photo of it, I think that each one of those little different, you know, 100 different contexts that you see with different colors and textures on the right, I think each one of those gets fully removed. And once it's all fully removed down to some base layer, that's what they call a stratum. I'm not entirely sure.
00:41:47
Speaker
But that would mean that roundness of the context, the organic shapes rather than being these cylinders sliced through cookie cutter style would be reflected then captured in the photogrammetry. That's what I think is going on, but I'm not sure. Again, that's of all the places that they had more detail than I cared about.
00:42:11
Speaker
This is the one that really, really I wanted to know and I don't have quite enough detail there. And I think it's just because there's some baseline assumptions about the way that they're excavating that I don't necessarily understand. I would, you know, have to have a conversation and have to be on site and see exactly what they're doing to fully get that. For sure.
00:42:32
Speaker
I mean, this is, this is super cool. And it seems like something that, I mean, obviously you need knowledge of how to put all this stuff together, but the, the collection of the data is something that could be done by almost any archeological team on the planet right now. Right. You're already doing.
00:42:48
Speaker
the steps necessary for the most part to be able to get here. You just need the equipment and the knowledge to be able to take the photographs, do the right drawings, take the right points and that sort of thing. So just modifying your data collection methods or augmenting them a little bit. And you could actually do this and it would not strike me as odd at all if one of these grad students or professors or whoever that is doing this ends up starting a company someday where they're just like,
00:43:16
Speaker
here's the kit, here's all the stuff you need that we need to make your models for you, collect all the data, send us back the equipment, and we'll send you all the models when we're done, right? But people are still, we're still in the phase where people are still just like figuring this out as they go, they're reading articles like this, they're listening to podcasts, they're figuring out, okay, well, this one said they use this, this one said they use this, I think I'm gonna try this, and then this, and they're, like you said, they're not really, they're kind of using a recipe, but there is no recipe. It's just like, here's what I want,
00:43:45
Speaker
And it's been done 100 different ways. So I'm hoping we get to the point soon where there really is a solid way to do this. I mean, obviously there would be some variation depending on certain variables. But there really should be just a handful of ways to start from nothing and get to these models that we want and make it replicatable. So hopefully we can get there soon. But it's pretty tech heavy. It's pretty high knowledge you need to get into Blender and even ArcGIS.
00:44:14
Speaker
whatever the hell they call shape. Is it meta shape? I think I always forget. I think they start with meta shape, but that's the current name of the software. Right, right. So anyway, it's promising. More stuff like this is what we need. More people figuring this stuff out. I love it. And before we go, I'm just going to point out that
00:44:37
Speaker
They graphed all this onto their existing workflow because they were excavating a certain way. They were documenting a certain way. This became an add-on. The other add-on too. A little bit of equipment, a little bit of software. They give some prices. They give some time. It takes these things. A fair amount of know-how and an individual with that know-how that can then be
00:44:59
Speaker
devote a lot of their time in the field to doing that. And that's something that Marco and I talked about on last episode, how much time he spends processing, but also then managing his data. And that's something else they mentioned in this article that also boosts it.
00:45:15
Speaker
is that they tell their DMP, their data management plan at the end of the article, or toward the end of the article, explain what they do, how they name the files, how they store them.
Data Management Plans and Project Applications
00:45:25
Speaker
And that's something that matters to me because we're in the midst of grant writing right now for the Lagash Project, and that's a big part of what we have to document is what our DMP is. And so far, we
00:45:36
Speaker
We've been very good about keeping lots of data, but it's not structured. It's not organized in certain ways. And we need to formalize that. So for me, it was another little piece of, oh, here's how some people are doing it. Just like my interview with Marco is, here's how one person who I know does good work is doing it. You know, a lot of things that I can just kind of mull over. Again, back to that, watching the chef, it's, you know, it's watching
00:46:02
Speaker
Julia Child, Jacques Papin, whatever on their cooking show and maybe not following along step for step, but getting a sense of what the triggers are. What are they trying to get out of the heat or the oil or the salt or whatever it is that they're working with at the moment for an end result?
00:46:24
Speaker
regardless of all the finicky little details that might go into this article or go into that recipe, it's the overall how you get to something that is good and acceptable at the end. I think they managed to thread nicely in the article. I'm a little bit richer for having read it. Yeah, absolutely. I love it. Like I said, it's really cool that you might be able to use some of it at Lagash.
00:46:51
Speaker
at least their data management plan and, you know, take something from it. And I hope other people can too. So I don't think I have much more to say on this you Paul. Oh no, I've said plenty about it. Nice, nice. Well, you know what? It's interesting that we had, uh, and this doesn't count for the drinking game, you people out there. It's interesting that we had an entire discussion about photogrammetry and didn't once say the word drone. I'm just saying.
00:47:17
Speaker
To their credit, they do mention drones in the article. Right, but they do. They do. Yeah. So they have to take a drink. Exactly. But that's another one of those things that I just love about where we're at right now in early 2023 is that we didn't have to mention drones. We don't have to mention how do you take photographs. We don't have to mention those things. I didn't have a chance to read this fully and into the really detailed sections of these, but I would imagine
00:47:45
Speaker
They're using not only the aerial drone photography, but also photographs of units close in and things like that to kind of bring all this together into a thing. And that's just the standard suite of photographs that you take. But that's the thing is, it's kind of standard now, right? If you're going to do this, you know that that's another piece of equipment and skill set that you need to have and able to be able to really get it done. Right, actually. And that's where I'll just end. My last comment is that kind of standard.
00:48:12
Speaker
This is the next little piece of the puzzle. This is where it pushes beyond just making your photogrammetric model with meta shape or drone deploy or open drone map or whatever you're using, which a lot of people are doing now to everybody's credit and to everybody's benefit, but pushing it beyond that to, okay, let's try to actually reconstruct a site.
00:48:36
Speaker
Yeah, for sure. So that's another thing I really like about it too, is that reconstruction aspect of it. Because archaeology is, and especially excavation, is inherently destructive. We are never going to see that site again in the same way that it was. That being said,
00:48:53
Speaker
I might be able to take something like this someday and just play with the entire thing in my Oculus Quest 2. Just jump into it, move some levels around, see what it looked like originally, push everything back with my hands and just dive down a couple of levels and see what it looks like there. Pull this shape out, pull this context out, just like Iron Man.
00:49:14
Speaker
the Iron Man movie where he's manipulating all that stuff, like with his hands, just something like that. And I see that we're getting really close to having the data to be able to do that. We may not have the tools to do that yet, but we're creating the products that we're going to need to be able to do that with. So I love it. Yeah, absolutely. All right. Well, with that, I think we'll say goodbye and we will see you guys in a couple of weeks. Bye, Chris.
00:49:43
Speaker
Thanks for listening to the Archaeotech Podcast. Links to items mentioned on the show are in the show notes at www.archpodnet.com slash archaeotech. Contact us at chris at archaeologypodcastnetwork.com and paul at lugall.com. Support the show by becoming a member at archpodnet.com slash members. The music is a song called Off Road and is licensed free from Apple. Thanks for listening.
00:50:08
Speaker
This episode was produced by Chris Webster from his RV traveling the United States, Tristan Boyle in Scotland, DigTech LLC, Culturo Media, and the Archaeology Podcast Network, and was edited by Chris Webster. This has been a presentation of the Archaeology Podcast Network. Visit us on the web for show notes and other podcasts at www.archpodnet.com. Contact us at chris at archaeologypodcastnetwork.com.