Category Archives: GIS and Remote Sensing

Archy vs. Angel Mounds.

In case you didn’t know what Angel Mounds is, I will link you to the web site. In case you didn’t know what I’ve been doing lately, I’ve been digging at Angel Mounds, to which I link you to our Field School Blog, and you should go read it. Doo eet.

I’ve been here for a week now and we are just now opening units up. Let me explain why it’s taken this long, because it’s actually a really cool reason.

Grad Mentor Matt with the Magnetic Gradiometer, walking lines to get a picture of the ground beneath.
Grad Mentor Matt with the Magnetic Gradiometer, walking lines to get a picture of the ground beneath.

For the first week we checked and set up the equipment we were going to use. Aside from the usual shovels and screens we’re using a Magnetic Gradiometer (aka Magnetomer or Mag for short) this year on pretty much all of the site we’re working on. This awesome little device use two sensors to measure the gradient of the magnetic field in the ground. It then creates a picture from those readings that can fairly accurately show where features are going to be on the site. It can’t show us depth and iron or magnetic metals will create these huge spots in the picture, but otherwise the picture is incredibly helpful in planing where to dig.

Magnetic gradiometer map of Prehistoric fire-hearths (site unknown). Image from Wikipedia.

So, now we have our own image of the site ground showing us a very interesting  image of the first terrace of Mound A. This allowed us to put in four 1 meter by 1 meter  units on the terrace right where the cool stuff is.

Honestly, this saved us tons of guess work and wasted effort, and really it only took one day to get the area surveyed and the image processed. Granted we did have to prepare the area and make sure any modern metal was well away from the area to be surveyed, so two days at max, and we (by we I mean Matt) covered a 60 meter by 60 meter area in a couple of hours. That’s pretty good.

I really can’t explain how much time and man power this saved us, or really how awesome cool the picture is.

Sharpeing trowles
Learning how to sharpen our trowels into razor sharp objects.

But all that was done last week, which means that today we actually BROKE GROUND! (Que Fan-Fair and Confetti!)

We opened four 1 meter by 1 meter  units on the first terrace of Mound A. All of them placed over places where the Mag showed us anomalies. Now, I am used to much bigger units, but I am also used to blindly digging based only on land forms and previous surveys. This is much better. Survey taken, spots identified, units opened, done.

Dr. Bill Monaghan from IU using the Total Station to locate and record points on the site grid on the terrace.
Dr. Bill Monaghan from IU using the Total Station to locate and record points on the site grid on the terrace.

For those who don’t know, the first step here is setting up a grid. Which I am not going into this time. (Did I mention our Field School Blog and how you should go read it?) Once we’ve got that done and we have the Mag image, we picked out smaller areas for the units, which also had to be shot onto the grid using the Total Station (pictured above). If you’ve ever seen a survey crew on the side of the road, that’s the camera looking thing on a tripod they’re using. We use them to for the same reasons and then some. (again, go read the blog)

Once we have two points representing our North line recorded by the Total Station we set about laying in the other points using the age old method of tape measures and math.

Learning to lay in the other two corners of the unit via tape.
Learning to lay in the other two corners of the unit via tape.

Once this is done the real fun begins, because now we can begin to dig. Which is much more then just sticking a shovel into the ground. See, we try and preserve the sod cap, or the grass on top. Usually because we plan to replace it afterwards. So because of that, there is a very specific way to remove the grass on top. (Also, we don’t want to screen the grass, because that takes forever and there is rarely anything useful in the grass.) What is this mysterious technique you ask? I call it, Sharpened Shovel Style!

See, we take square shovels (as opposed to spade shovels), sharpen them like knives, and then chop into the grass just far enough to get past the roots, but not really into the dirt much. Then we pry the grass up and roll it up and set it aside till we need it again. It sounds simple, but it can take a bit to get just right.

Popping the top off the unit.  Note the perfect form...
Popping the top off the unit. Note the perfect form…

Once that’s all gone we begin removing the dirt in arbitrary levels, unless the soil changes or we see a feature, and we begin taking copious amounts of notes. Seriously  we take so much paperwork it makes the trees cry! But we have too, see excavation is destruction, and even with doing as little damage as we will be using the Mag image and all, we still need to record everything we do and find so that later we can reconstruct the events of the excavation via the paperwork.

Grad Mentor Erica teaching us how to fill out the paperwork.
Grad Mentor Erica teaching us how to fill out the paperwork.

We also tag every bucket of dirt that we plan to screen. Which bring me to the next new thing we’re doing here that I’ve not seen done on a CRM site yet. Water Screening! (I’m not saying it doesn’t happen, just that I haven’t seen it yet).

Filling out the tags that will go with the buckets of dirt to the water screens.
Filling out the tags that will go with the buckets of dirt to the water screens.

So, Water Screening is basically regular screening, where you take a bucket of dirt and sift it through a metal mesh screen stapled to a wooden box frame, and you add water. Lots of water, like from a hose. When you do a big dig, or a phase 3, you move a lot of dirt and to get though all of it, you usually have dedicated screeners that rotate with the diggers. You also have large screen tables so you can work on more than one bucket of dirt at a time, making sure it’s all from the same level.

The Water Screens
Setting up the water screening tables.

Water screening works the same way except the screens are a much finer mesh and not metallic, and you get to play with the garden hose. Oh and mud, there is lots of mud.

water screening
And mud.
Playing with the hose.
Playing with the hose.

The benefit of this versus dry screening is a near 100% recovery of anything that comes out of the unit. Also, you get to play in the water on really hot days.

So, that was pretty much what happened on day six of my field school here at Angel Mounds. All the hard work from last week payed off and now the new hard work of digging begins. Interesting features await us beneath the soil on Mound A, and we’re going to find them.

Waiting to dig.
Waiting to dig.

“But wait Archy, where are you in all these cool pictures you just showed us?” 

Where you ask?

Remember how I was telling you about the Magnetic Gradiometer? I was out there pulling tape so that Matt would know where he needed to walk in order to survey more of the area around Mound A. That’s right, there will be more units, and one of them has my name on it. (Seriously, I’m taking a Sharpie to it or something).

Me and my awesome hat, be jealous, it's a Tilley.
Me and my awesome hat, be jealous, it’s a Tilley.

How did the Easter Island Statues Get There? They Might Have Walked!


While doing research for my Remote Sensing project I happily stumbled across an entry in the book, Satellite Remote Sensing for Archaeology by Sarah H. Parcak, that I just had to look up. Once I got into it, I knew I had to share, since more than a few have asked about this very topic. Specifically,  how the Easter Island Statues were moved. Well researchers Dr. Carl Lipo and Dr. Terry Hunt might have an answer, using Remote Sensing!

Moai set in the hillside at Rano Raraku

First, What are the Easter Island Statues? Officially called the Moai, they are stone monoliths depicting giant human figures with extremely large heads. The stone they are carved from is called  Tuff, which is an easily carved,  compressed volcanic ash [Radford 2012]. The tuff quarries are located in an extinct volcano called Rano Raraku on the northeastern part of the island [Radford 2012]. Experts, and locals, attribute them to depictions of ancestors and great leaders. Others, attribute them to, yes, Aliens and the like.

Before we get into what they found let’s look over some of the alternative theories out there.

The site called The Hidden Records is kinda typical of the kind of ideas Ancient Alien Theorists get. I like this one, mainly because it’s written by a guy named Wayne, who likes to refer to himself in the first person. This amused the Archy, so the Archy decided to peruse the Wayne’s entry on the Moai.

I’m not going to lie, I skimmed this site. It took a while for Wayne to get to the point, which was that the Moai are somehow connected to an ancient global cult who worshiped bird-headed spacemen, as shown by the dubious claim that the statues are aligned with the “Sol-Star”. Also, carved onto the bodies are both the symbol ‘O’ and ‘M’ which, other than being two of the most simplest symbols to form, also connect the statues to the global Space-BirdMan cult.

Wayne did throw a few questions out there, and a couple really caught my attention, mainly because they were so easily answered. Not that this will impress the Wayne, he’s sure to point out, he’s never heard a satisfactory explanation for the correlations he sees, but that’s a true believer for you. These questions are pretty common among any conspiracy/true believer I’ve encountered.

“How strange is that just for starters? The first expedition unearthed them and documented the breaking discovery pictographic[sic] evidence, didn’t make it public in a big way at all, then for unknown reasons, buried them again! This is insane! What could have been so shocking for them to have been completely covered up again?”

This comment comes after a ramble about the excavation of a few of the Moai statues. They were indeed excavated, and they do possess detailed bodies beneath the ground, but this comment shows Wayne’s lack of understanding of how archaeology works. It also makes several assumptions that are not validated.

Firstly, Wayne assumes the statues were originally buried. What Wayne doesn’t seem to understand is that really heavy objects sink over time, especial when they are sat on bare ground. We see this a lot with headstones in cemeteries. The weight of the stone forces itself to sink into the ground over the years, especially in regions where there is rainy weather that softens the ground seasonally.

Secondly, it’s not so shocking that the archaeologists would have reburied the statue, it’s actually a very common practice that helps to preserve a site or object. Nearly everyone does it, especially when we’re looking at things that we are not intending to remove or if a dig takes more than one season. For some reason Wayne thinks that all archaeologists do is dig things up, rip them from the ground, and then scamper off to a museum. Lots of things get left in-situ for prosperity and because the point was to examine them, not abscond with another culture’s artifacts.

Third, Wayne assumes, as many alternative theorists do, that there is some great academic conspiracy that every “mainstream” researcher is in on. Therefore the researchers who worked on the Moai dig kept their findings quiet and then tried to hide the evidence because it’s so shocking. The reality is that there is a lot of academic research on the Moai and it’s very accessible to the public. Including the site the Easter Island Statue Project which is a great resource for those with questions about the Island and it’s ancient culture. They have links to their expeditions,  excavations, and artifact logs. Dr. Hunt also makes his research accessible to the public via his personal  page.

Moai facing inland at Ahu Tongariki, restored by Chilean archaeologist Claudio Cristino in the 1990s

But Wayne goes on. This time about how he can’t possibly figure out how two civilizations develop independently of each other.

“By chance having two individual civilisations[sic] on opposite sides of the planet, one located in the middle of an ocean, having the same obsession with massive stone carvings and showing the same symbols, story, style and entity appearance is absolutely mind blowing!”

This is actually called Convergent evolution and applies easily to cultures as well as species. What I don’t understand is why people don’t get that we are all humans and each of us just as capable as the other. So why is it so hard to grasp that two different cultures can come up with the same idea? Especially when they live on the same planet, encounter the same natural forces, look up at the same sky, and share the same biological needs? Wayne seems to be amazed that multiple cultures could look up at the starry sky at night and come up with constellations completely independent of one another. That idea confuses him, but a global Space-Bird Cult is completely reasonable.

It’s also a very sad statement how intellectually poor Wayne, and most that think along these lines, think our ancestors were. Apparently, our ancestors were so intellectually deficient that they couldn’t possibly figure out how to carve stone, make symbols into words, and have their own cultures without Spaceman helping them out. It’s terrifically insulting to ancient cultures, and vaguely racist. As usual, these claimants are very white, and well, the Rapa Nui (who are the descendants of the Moai culture) are kinda brown-ish. It’s more of a micro-aggression then full-blown racism, but it’s a common thread in these “ancient people were visited by aliens” theories, and people need to be aware of it.

Anyway, I could spend all day breaking down the Wayne’s arguments, but I think we all get the idea. There are people out there who think the Moai were either built by aliens or for aliens.

So how did these huge Stone statues get from their quarries to where they are now? Well, they walked. According to the History Channel’s excellent mockery of a documentary called Ancient Aliens, when the Spacemen came down and had the statures carved to fit their egos, then they animated the statues so that they would walk to locations they would be found at.

The “Walking” Moai, via

But the History Channel may not be as wrong as they usually are. This time there is a bit of meat to this idea. Hunt and Lipo reproduced the “walking” of the statues by having three teams maneuver the statue using ropes [Boyle 2010]. It’s more fun if you watch this video:

[Boyle 2012]

But honestly, that’s not the coolest part for me. The coolest part is that Hunt and Lipo also have used infrared-satellight images to identify the very roads that the statures were probably walked down. These roads have been set upon by the natural processes that occur over time, but that’s whats so damn cool about using remote sensing, you can see the scars left behind by ancient peoples on the landscape!

“Figure 1. A panchromatic 70cm resolution QuickBird satellite image showing an ancient road section leading west-south-west from the Rano Raraku statue quarry (A). Statues that surround the quarry are easily visible in this image (B) as is the modern parking lot (C). The ancient road (D) is visible primarily as a horse trail and as a line of vegetation that runs from the north-east to the south-west corner of the image. This feature likely reflects sediment compaction with greater water retention and subsequent vegetation growth. Multiple large statues (moai) line this road near the quarry (E). The satellite image was provided by RADARSAT, Inc and DigitalGlobe, Inc.” [Lipo and Hunt 2005]
That’s pretty darn cool to me. You should be able to click through the image to get to the full paper. The picture is much nicer in the pdf version.

I was really excited when I saw this little tidbit, and I really wanted to share it with you. The more I learn about remote sensing the more I am stoked about learning to use it to aid in archaeology. Especially since I know this paper was used to help Lipo and Hunt from their “Walking Statue”  hypothesis  which led to the testing of it, which aids in the debunking of sites like The Wayne’s.

Dr.s Lipo and Hunt [Boyle 2012]
I want to leave you with one last quote from the Cosmic Log article because this really drives home the damage that racism of the Ancient Alien theorists cause:

“So did the statues rock, or roll? The debate over the two scenarios surrounding Easter Island’s past could well continue for generations. But it’s clear which scenario is preferred by the islanders themselves.

“The young people … they’re celebrating. I don’t think there’s any other word for it,” Hunt said. “One came up to me and said, ‘It’s so important for my generation to know we’re not failures.’ That brought tears to my eyes.” [Boyle 2012]


Boyle, Alan

2012  How Easter Island’s Statues Walked. Cosmic Log, NBCNews.COM. Retrieved Nov. 8 2012

Lipo, Carl P. and Terry L. Hunt

2005   Mapping prehistoric statue roads on Easter Island. Antiquity vol 79: 158-168. Retrieved Nov. 8 2012

Radford, Ben

2012   Did Aliens Visit Eater Island? Discovery News. Retrieved Nov. 8 2012

Van Tilburg, Jo Anne and Cristián Arévalo Pakarati

2012  The Easter Island Statue Project.  Retrieved Nov. 8 2012