3D Modeling an archaeological site during excavation

I've been playing a bit with improving the photography during excavation at the site, including better and easier overhead photos (more on that soon). This season, when I was looking at a bunch of overheads I had taken, it occurred to me that I could likely generate a decent 3D version without too much more work using the AgiSoft PhotoScan software I had purchased a few months ago.

I threw the photos into the software and got the following (which I'm showing here as a screenshot). You can see big holes where the sides of the walls are not missing due to the overhead shots being fairly vertical and therefore not capturing the sides, but overall it looks pretty good and certainly made it clear that it was possible to generate good 3D models from photos taken in a few minutes on site. So the next time, I took not only a series of overheads but also a number of shots from ground level, circling the area I was photographing while snapping shots.

Here's what that approach yielded, here in a screenshot, but for the full effect, head over to the publicly available version at p3d.in, where you want the "burial" model. I've still got to work on optimizing the conditions in the modeler for getting good results: it's easy to generate something of the quality you see here, but getting better results takes a lot more cpu time and I haven't worked out a good workflow yet. Expect some more posts on this in future weeks.

What am I going to use these for? Well, first off they look pretty cool, which is something not to be neglected. It's a lot easier to capture people's imaginations when they can play with a little 3D version of a site. Second they of course form a more sophisticated documentation of the site for human viewers. Manipulating the model helps make clear in a way that 2D photos can't how various objects related to one another. Ideally the models will eventually be of good enough quality that we can do measurements on them. You can check out the meter stick in these images already (20cm to each red and white band). We try to capture relevant locations in our total station, but it's easy to miss something and the models mean we have less to worry about. It would also be great to incorporate the digital models into our GIS system. Right now they're already useful in reminding us just what everything looked like at a certain point in time, but it should be possible to make them part of our long-term digital database.

Other people are doing this sort of thing too. For example, check out William R. Caraher's blogpost on a talk back in April and his more recent one last week and another encouraging others to blog about their work (which is in part why I wrote this!). There's a little Twitter activity too, so go have a look at @BillCaraher @adamrabinowitz @sebhth @Pompeiana79 @adreinhard.

First (Half-)Week

We're at our first weekend now, having started on Wednesday. It's rained a bit...OK, it rained a lot on Thursday afternoon, and it's raining lightly this morning. The students have all headed off the Perugia, where we believe a visit to the chocolate factory is on the agenda. The staff are planning an outing to somewhere too.
On site, we've started in with three test trenches, placed according to the results from the geomagnetic surveys of previous years. The water table continues to be much higher than it was in our firs two seasons, perhaps higher even than last year, which means that it still covers the lowest strata we excavated in '08 and'09. This is not helpful. Two of the test trenches are still not quite through the topsoil, so not much to report there.
A presto!

Google Earth

Sitting here on our GIS workshop at Drew, it occurs to me that I have never posted a Google Earth bookmark for the site. So here's one for the church of S. Maria in Pantano. We excavated just north of the church.

Fun with Satellites

Drew prides itself on its incorporation of technology into learning. Me too...or maybe it's more accurate to say that I just like playing with computer stuff.

In any case, I'm incorporating a few fun technologies into the dig and courses for this summer, mainly to do with mapping. The first one relies on all those satellites the U.S. has put around the planet in order to provide itself (and incidentally the rest of us) with a fairly good idea of our position on the globe. These Global Positioning Satellites provide a constant stream of data that can be read with all sorts of GPS devices, and now I've got three of these babies: the GT-31 from Locosys. (I got mine from The Midwest Speed Quest link on that page. This is a windsurfing site: these units are waterproof and float.)

They don't show maps like the units found in cars, but they do track and store your position so that you can download it later. In fact you can create multiple tracks and save them onto an internal SD card for transfer to your computer. On your computer, you can run some free software that converts these files into numerous formats, including Google Earth's native kml and the file format for OpenStreetMap.org, which is how we're going to use them in Italy, but more on that another time.

Meanwhile, here's a screen shot from Google Earth. I got hungry and went to get some hot-and-sour soup (gratuitous unnecessary personal information, just like a real blog!), and took along the GPS unit. You can see that my path isn't perfectly mapped - I didn't stagger all over the street on my way there - but it isn't bad either. (Click on it to download the Google Earth file.)