Photogrammetric Model Made With Iphone 4s

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I’ve experimented before with using my Iphone to create Photogrammetric models (not through the app, just taking the photos and running it through the Windows version of 123D Catch), with interesting but not perfect results. The other day however I found myself with a nice complete in situ sheep skeleton and no camera, so I took the opportunity to test the technology once again.

I took 49 photos with a very good uniform shade, going round the skeleton at first and then concentrating on tricky parts, like the head or the ribs. I then run it through 123D Catch and found that almost all of them had been stitched. I think the lighting really did the trick, as it created a really nice contrast between the bones and the ground, The photos were taken just as the sun had set, so it was still very light, but with no glare.

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The skeleton itself looks extremely good compared to some of my earlier tests. It can be viewed here in rotatable 3D: https://sketchfab.com/show/b0ef1638d4714fcdab59c040cdb46923
I particularly like the relatively sharp edges that I really couldn’t achieve with the other models, and by looking at the cloud point I found it to be quite accurate regardless of textures. In addition to that it’s coped excellently with the rib that pokes out of the ground and the pelvis, both of which I was absolutely sure it would have a problem with. Overall I’d say the model was nearly as good as some of the models I have done with a standard camera, and I think the potential is definitely there.
The only issue I have with using the Iphone camera is that it’s still an unreliable method. I tried replicating the results today as it had been cleaned better, but the new model is more blurry, again probably due to slightly less ideal lighting conditions. Therefore I would still use my camera as much as possible, and save the Iphone for those situations in which I find myself unprepared.

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First Photogrammetry Article Published

New Photogrammetry Article

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I’m very glad to present you with my first (but not last) published article on the topic of Photogrammetry in Archaeology! The December edition of The Post Hole, that has recently been released, features a paper on “The use of Photogrammetric models for the recording of archaeological features”, which I wrote during the summer, and which I’m sure you will find of some interest.

It deals specifically with archaeoloogical features on site, and it looks at accuracy, methodology and uses, especially when it comes to recording. The aim of it is to show that far from being technology for technology’s sake, Photogrammetry can contribute greatly to our understanding of an archaeological site, as well as reinforce and improve traditional methods of recording such as section drawing and plans.

The article is based on a few sites I worked on, and that have featured on this website before, such as Ham Hill and Caerau.

This is however just scratching the surface of a technology that is now appearing more and more frequently in publications, and that will eventually become a fundamental part of archaeological recording.

Ham Hill Iron Age Skeletons Turn Digital

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Three of the skeletons found at the site of Ham Hill, Somerset during the 2013 excavation are now available to view online at the following links:

https://sketchfab.com/show/70d864c4736435710bc65b6f21d81c03

https://sketchfab.com/show/821565c7ce0b98e1b7764c73a9f07492

https://sketchfab.com/show/fa694aff0fb5949e2f396a5fb2da37b0

The skeletons were discovered during this year’s excavation carried out by the Cambridge Archaeological Unit and Cardiff University, at the site of an important Iron Age hill fort. They are only some of the many human remains found, some of which were carefully placed within a number of pits, while others were located symbolically within an enclosure ditch, often with body parts missing.

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The models themselves were made using Photogrammetry and specifically 123D Catch, which required very little time for quite good quality. The aim of this was to preserve a record of the skeletons in situ for further interpretation once they had been removed from the location they were discovered in.

Given the complexity of the subject, the results seem to be very promising. Time was a big factor when making the models, as they had to be removed before damage occurred. Some of them were also in tight spots, which made it hard to access some of the standard angles, but overall this was counterbalanced by taking a larger number of photographs than normally (around 30 per skeleton). The lighting conditions also proved to be ideal, as there was an overcast sky, but also sufficient sunlight coming through to really emphasise the surfaces.

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For further information on the skeletons I suggest reading the article at http://www.bbc.co.uk/news/uk-england-somerset-23928612

Photogrammetry in Archaeology: Examples

I decided to make a video to show you some of the work I’ve been doing with 123D Catch and archaeological features. There’s not much to say about this one as the video is self explanatory, so just thanks for watching.

Using Photogrammetry with Archaeological Archives: Must Farm

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About a year ago I volunteered at the Cambridge Archaeological Unit for three weeks, during which I had some time to carry out some experiments with Photogrammetry with the help of some of the people there. One of the projects I carried out involved using the photograph archive they had to create 3D models with 123D Catch, to see if it was possible to create models from photographs not taken with this purpose in mind.

Looking through the archive one site in particular caught my eye, as the photographs perfect for this use: Must Farm, Cambridgeshire. The site itself is extremely interesting, and has won a Site of the Year award for the level of preservation. It is mostly a Bronze Age site, and throughout the years it was excavated it revealed a series of intact wooden boats, as well as a living structure which had collapsed into the river, waterlogging the timber frames and all that was within, including weirs and pots with food residue. For more information visit the official website http://www.mustfarm.com/.

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The photographs I found were from the 2006 excavation, and they consisted of series of shots from similar angles of same objects. The number of images per feature was around 8, depending on what it was. The most common things photographed were waterlogged wood beams, pottery spreads, sections and weirs.

Generally, the number of images and the fact they were all taken from a very similar angle would mean making a model is impossible. But through different test I have found that there is an exception to this rule when the object is particularly flat. If you are photographing a wall, there is no need to go round it to create a model, all you need is to take the images from the front and then change the angle slightly. The idea is also at the root of Stereophotography, in which two images at slightly different angles give the illusion to our eyes that they are in 3D. Similarly modern 3D films use a similar idea, with incredible results.

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Running the images through 123D Catch provided the proof of this theory, as in out of 40 or so potential models, around 70% were extremely good. The models had all the detail of a 3d model made with intentional photographs. Some details could have been a bit better, like some models of timber sticking out of the ground, for which only the front is available as would be expected, and the side of protruding objects which are blurry, but overall the results are amazing for what they are.

Most of the models are now available at http://robbarratt.sketchfab.me/folders/must-farm

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If we consider the amount of archaeological photographs that are taken at every site, surely amongst them there is enough to create at least some fantastic models.

8 Reason Why We Should Be Using Photogrammetry in Archaeology

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If you are an archaeologist you should be using Photogrammetry because:

  1. It is easy to use: Unless you are dealing with something extremely large or extremely complex, Photogrammetry has an extremely high success rate. When it was still based on camera calibration, complex calculations and precise measuring was necessary, but with more modern programs often all that is needed is to take the photos and upload them. Decent models are easy to produce, and more complex ones are achievable without issue with some experience. Overall, anyone could potentially use it in small scale archaeology with no experience, and on large scale with limited training.
  2. It is quick: With a good internet connection I can probably model a single feature in under 10 minutes. And by single feature I mean anything from a posthole to a stone spread. In situ finds could be recorded in no time, cutting back on the need to plan everything by hand. A complex stone wall could be preserved for the archaeological record simply by taking a few dozen photographs, and sections can be recorded with much more realism than any hand drawn plan can achieve. A rough sketch of the section would of course help the interpretation, but the measuring time would considerably go down, as it would be possible to measure on the model using Meshlab.
  3. It is practical: Laser scanning is the current fashion in archaeology, but the problem with laser scanning is that you need to provide expensive equipment, you need to carry that equipment around and need to train specific people to use the machines and the software. Photogrammetry requires nothing more than a camera and a laptop, which are usually much more accessible on site. If a delicate object is found, that may not survive excavation, it is much easier to take some photographs with the site camera, to then edit later, than to bring in the equipment to laser scan it.
  4. It is accurate: As shown in one of my recent posts, the accuracy of 123D Catch is extremely good for the type of process. Although it cannot compete with that provided by laser scanning, an error margin of less than 1% means that any task required for interpretation can be carried out without having to worry of the results. The level of accuracy is ideal for presentation, for interpretation and for recording.
  5. It is photorealistic: No other technology gives you the photorealism that can be achieved by Photogrammetry. Due to the fact that at the base of the models we have the photos, and that the finished product contains .mtl files that record the exact position of the photographs, the surfaces of the features can be recorded as they are in real life. The models seem realistic because they are not a simple collection of points, but a combination of points and images.Image
  6. It is entertaining: Archaeology is not simply about recording the past, it is also about getting the information out there, to the general public. It is important that anyone interested in an archaeological has the opportunity to learn about the site itself. Academic texts are amazing when carrying out research, but for the average archaeological enthusiast, who lives in a now mostly digital world, texts can be seen as confusing. Photogrammetry provides a visual component to the archaeological record, making it possible for people to see from their own living room the archaeology, as if they were actually present at the site.
  7. It is constantly improving: At the moment there are some problems and flaws with the programs that may cause concerns to more traditional archaeologists. These problems however are only temporary. With such a great interest in the digital world, teams of developers are constantly trying to update and improve all software, and if at present programs like 123D Catch are not perfect, they can only get better. Also, 10 years ago this level of accuracy in Photogrammetry was unheard of, yet today it has got to this point. In another 10 years how much will the programs change for the better?
  8. It is not as simple as it looks, in a good way: There are different levels to Photogrammetry. The basic level is the simple recording of features and artefacts for the only reasons of recording and presenting. There is however a second level, which uses the models created to analyse archaeology, like I show in my previous post about finding inscriptions in coins. There is a third level, which alters the way the programs are used, by changing a part of the process to get greater results. An example is the attempt I did on reconstructing the Sphinx using tourists’ photographs, or the idea of using series of photographs in archaeological archives to reconstruct features long gone. Finally the fourth level is the more interesting one. It’s using many Photogrammetric models to create a single model, i.e. recreating pots by putting fragments together digitally or entire sites by gluing together individual features. So it is not only pretty models of features, it is much more.Image

Using 123D Catch to Record in Situ Finds

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If you have the pleasure of excavating a collection of finds rather than an individual one often one of the problems you will encounter is how to record it in situ. Some finds are delicate and may well break up once removed from the soil, while others may have been placed in a specific way and as such their location is important. Traditional methods require planning of the finds, but Photogrammetry may offer an alternative to this, by creating simple models and allowing an accurate record of the finds as well as the surroundings.

It is a non-destructive process, and has the advantage of being quick and efficient. In addition many shots can be taken at different times to show the entire excavation process.

Here are some examples from Must Farm (2006) that were originally photographed without Photogrammetry in mind:

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The links for these models can be found here:

https://sketchfab.com/show/gvQKa4WkUPOTaegyWcOUMZQlOSH

https://sketchfab.com/show/cf038e102fcb484aa71818a46be6a4ec

https://sketchfab.com/show/vun3L1S0bb1tl0uEC4ilV9Gpmhk