Documentation of a bas-relief on a cliff : the workflow

This summer, between May and June, we worked for a joint mission, led by the University of Innsbruck (Institut für Alte Geschichte und Altorientalistik) and the Cultural Heritage, Handcrafts and Tourism Organization of Iran. The project was held in Firuzabad, in the Pars Province of Iran. We will write more details about this work in the next post. By now I just want to use some material we collected to illustrate the work-flow in data acquiring during an archaeological documentation of a bas-relief on a cliff.

The video below shows the overall process.

You can see the initial preparation phase (1), during which we placed the Ground Control Point (GCP) to perform normal 2D vertical photo-mapping and to rectify and georeference the 3D point-cloud. Than (2) we collected pictures with three different flights of our DIY drone, in order to use them with different open source SfM/MVSR software (PPT, openMVG and MicMac), to reach the best possible result: a couple of flights with parallel camera, to have a good superimposition of the whole bas-relief, and a higher acquisition to cover the upper details. In the meantime (3) another operator (+Rupert Gietl) was collecting pictures from the ground, to register also the lower perspective. Later (4), I prepared the total station and collected the GCP, thanks to some fixed points we placed the day befor (0) with our GPS. Finally +Rupert Gietl  took the last (very close) details photos, using a ladder.
The entire process lasted more or less four hours, but we needed some more time the day before to place the fixed GCP down in the valley (in international Geographic Coordinates System). A good part of the work involved just the logistics or the approach to the site, and has been slowed by the transportation of the necessary equipment (ladder, total station and drone) through a couple of passages where it was necessary to climb some rocks.
It is interesting to note that it would not have been possible to accomplish this mission with a commercial drone, due to the embargo rules (which are currently under revision), while with a DIY hexacopter it has been simple to disassemble the components which were not allowed (like the FPV system ore the GPS controlled flight).
I hope this post was useful, have a nice day!

The archaeometric excavation

Last year, on November 28, Arc-Team joined the conference "Lo scavo archeometrcio: scienza e tecnologia applicate allo scavo archeologico" (en: "The archaeometrcic excavation: science and technology applied to the archaeological excavation"), which was held in Rovereto (Italy) at the Museo Civico.

During the meeting we gave a presentation titled "Professional archaeology. Innovations and best practice with free technology. Toward an Open Research." Today I uploaded on our server the slides, so that we can share this work (like always under Creative Commons Attribution - CC BY).

As usual the presentation has been done with impress.js through the Graphical User Interface Strut (both GPL licensed) and it is optimized for Firefox or Iceweasel (better visualized here).

Here is a little explanation regarding the single slides:

SLIDE 1

A fast presentation regarding Arc-Team.

SLIDE 2

An animation representing the importance of geocoding in archaeology (from space to site).

SLIDE 3

Differential GPS and Total Station: the main tools needed by archaeologists on the field (to georeference every single element of the archaeological record).

SLIDE 4

Some examples of geocoding in archaeology: everyday work, project in extreme conditions and missions abroad...

SLIDE 5

... survay and excavations

SLIDE 6

In survay projects the geocoding tolerance for archaeology is higher, so that we are testing alternative solutions to build a low-cost and open source GPS with centimetric accuracy, using the software RTKLIB (or its port in Android)

SLIDE 7

All the recorded data (in 2D and 3D) can be imported into an open source GIS.

SLIDE 8

For aerial archaeology it since 2008 we are working with open source DIY UAV, like the UAVP or the KKcopter (in the slide).

SLIDE 9

Our last UAV prototype and an example of 3D pointcloud form aerial pictures.

SLIDE 10

Since 2014 we are testing DIY camera (using the filter of Public Lab) for NDVI and NGB pictures in archaeological remote sensing.

SLIDE 11

Just removing the IR filter, a normal camera can be used for endoscopic prospections in low light conditions.

SLIDE 12

In the field of geophysical prospections we use a DIY  machine for Electrical Resistivity Imaging. The data can be visualized in a GIS (e.g. GRASS GIS in the slide), using the east and north and the resistivity values.

SLIDE 13

Some geoarchaeological analyses can be performed directly on the field, like the settlement test (using the soil triangle) for the texture or the lithologic recognition for the skeleton.

SLIDE 14

Also some basic analytical chemistry can help during the excavation (giving indications on the ancient use of the soil), to verify the presence/absence of phosphates or of organic remains.

SLIDE 15

Other preliminary laboratory (flotation and sieving) analyses can prepare the samples for further investigation. Also in this case we use a DIY machine.

SLIDE 16

Colorimetry can be performed in many ways. Currently we are testing different options, like the open source spectrometer of Public Lab.

SLIDE 17

For some laboratory geoarchaeological analysis (e.g. microscopic morphology) we use normal optic microscopes, while for more advanced studies we externalize the service (e.g. SEM or energy dispersive x-ray spectroscopy)

SLIDE 18

Currently we are testing the potentialities of the FLOSS MorphoJ to speed up the process in carpological remains recognition

SLIDE 19

To document archaeozoological remains in the field, we use the standard digital documentation techniques (in 2 and 3D), with FLOSS (e.g. bidimensional photomapping with the Aramus method or 3D recording through SfM and MVSR)

SLIDE 20

In the evolutionary anthropology field we developed a new technique (anatomical deformation) thanks to the FLOSS Blender

SLIDE 21

The same software (Blender) is used in the process of archaeological forensic facial reconstruction

SLIDE 22

Open source GIS (e.g. GRASS) are the main software we use to process and manage the recorded data

SLIDE 23

Thanks to open source UAV and Blender we experimented new ways to disclose archaeological data in a four-dimensional way (x,y,z,t)

A more detailed explanation of the entire presentation will come soon with the related article. For the topics which were already discussed in AOTR, I suggest to read the related post (see the above bibliography). For the latest experiment (e.g. near infrared, NDVI and NGB; Electrical Resistivity Imaging; Sedimentation test; litologic recognition on the field; flotation and sieving; colorimetry; microscopic morphology; MorphoJ;), we will try to write something as soon as possible.

Bibliography

Lo scavo archeologico professionale, innovazioni e best practice mediante metodologie aperte e Open research (here on Research Gate and here in Academia)

Webography (from ATOR):

3D and 4D GIS

gvSIG

SfM and MVSR

PPT-GUI (tutorial); from pictures to mesh (PPT, MeshLab, Blender); PPT with Bundler MultiTread; PPT with turntable (not recomended); PPT VS MicMac; PPT VS openMVG; recovering old data; underground documentation; big data; low-light conditions; underwater archaeology; aerial 3D; 3D GIS; anthropology;

Aerial 3D documentation

Caldonazzo Castle (case of study);

Archaeological endoscopy

normal endoscopy; IR endoscopy;

Geoarchaeology

genetic color, framework and edge analyses of skeleton; analytical chemistry on the field;

Archaeobothany

Vegetal macro remains indentification;

Evolutionary anthropology
Anatomical Deformation Technique (ADT): validation; ADT Paranthropus boisei; ADT Homo rodhesiensis;

Archaeoanthropology
Archaeological Forensic Facial Reconstruction (AFFR); Digital AFFR: technique validation; AFFR: state of the arts; AFFR: poster;

Archaeological dissemination
Caldonazzo Castle 4D (case of study);

From drone-aerial pictures to DEM and ORTHOPHOTO: the case of Caldonazzo's castle

Hi all,
I would like to present the results we obtain in the Caldonazzo's castle project. Caldonazzo is a touristic village in Trentino (North Italy), famous for its lake and its mountains. Few people know about the medieval castle (XII-XIII century) whose tower is actually the arms of the town. Since 2006, the ruins are subject to a valorization project by the Soprintendenza Archeologica di Trento (dott.ssa Nicoletta Pisu). As Arc-Team we participated in the project with archaeological field work, historical study, digital documentation (SFM/IBM) and 3D modeling.
In this first post i will speak about the 3D documentation, the aerial photography campaign and the data elaboration.

1) The 3D documentation 

One of the final aims of the project will be the virtual reconstruction of the castle. To achieve that goal we need (as starting point) an accurate 3D model of the ruins and a DEM of the hill. The first model was realized in just two days of field-work and four days of computer-work (most of the time without a direct contribution of the human operator). The castle's walls were documented using Computer Vision (Structure from Motion and Image-Based Modeling); we use Pyhon Photogrammetry Toolbox to elaborate 350 pictures (Nikon D5000) divided in 12 groups (external walls, tower-inside, tower-outside, palace walls, fireplace, ...).

The different point clouds were rectified thanks to some ground control point. Using a Trimble 5700 GPS the GCPs were connected to the Universal Transverse Mercator coordinate system. The rectification process was lead by GRASS GIS using the Ply Importer Add-on.

To avoid some problems encountered using universal coordinate system in mesh editing software, we preferred, in this first step, to work just with only three numbers before the dot.

2) The aerial photography campaign 

After walls documentation we started a new campaign to acquire the data needed for modeling the surface of the hill (DEM) where the ruins lie. The best solution to take zenithal pictures was to pilot an electric drone equipped whit a video platform. Thank to Walter Gilli, an expert pilot and builder of aerial vehicles, we had the possibility to use two DIY drones (an hexacopter and a xcopter) mounting Naza DJI technology (Naza-M V2 control platform).

Both the drones had a video platform. The hexacopter mount a Sony Nex-7; the xcopter a GoPro HD Hero3. The table below shows the differences between the two cameras.

As you can see the Sony Nex-7 was the best choice: it has a big sensor size, an high image resolution and a perfect focal lenght (16mm digital = 24 mm compare to a 35mm film). The unique disadvantage is the greater weight and dimension than the GoPro, that's why we mounted the Sony on an hexacopter (more propellers = more lifting capability). The main problem of the GoPro is the ultra-wide-angle of the lens that distorts the reality in the border of the pictures.
The flight plan (image below) allowed to take zenithal pictures of the entire surface of the hill (one day of field-work).

The best 48 images were processed by Python Photogrammetry Toolbox (one day of computer-work). The image below shows the camera position in the upper part, the point cloud, the mesh and the texture in the lower part.

At first the point cloud of the hill was rectified to the same local coordinate system of the walls' point cloud. The gaps of the zenithal view were filled by the point clouds realized on the ground (image below).

After the data acquisition and data elaboration phases, we sent the final 3D model to Cicero Moraes to start the virtual reconstruction phase.


3) The Orthophoto

The orthophoto was realized using the texture of the SFM's 3D model. We exported out from MeshLab an high quality orthogonal image of the top view which we just rectified using the Georeferencer plugin of QuantumGIS.
As experiment we tried also to rectified an original picture using the same method and the same GCPs. The image below shows the difference between the two images. As you can see the orthophoto matches very well with the data of the GPS (red lines and red crosses), while the original picture has some discrepancies in the left part (the area most far away from the drone position, which was zenithal on the tower's ruin).

4) The DEM

The DEM was realized importing (and rectifying) the point cloud of the hill inside GRASS 7.0svn using the Ply Importer Add-on. The text file containing the transformation's info was built using the relatives coordinates extracted from Cloud Compare (Point list picking tool) and the UTM coordinates of the GPS' GCPs.

After data importing, we use the v.surf.rst command (Regularized spline tension) to transform the point cloud into a surface (DEM). The images below show the final result in 2D and 3D visualization.

Finally we imported the orthophoto into GRASS.

That's all.

A DIY endoscope for emergencies during excavation fieldwork

It happens somethime when we are digging: suddently an empty space appeasr under our feets. Normally it is just a small hole, but in some cases it is something bigger (and can be dangerous, expecially if buldozzers or other machines are around). In this video we show how we faced such a situation during an excavation inside a church. Using some material we had in the field (a broomstick, some adesive tape, a led flashlight and a wireless camera with a monitor from the remote sensing device of our UAVP), we build a DIY endoscope to check the underground situation. The interesting thing (IMHO) is the possibility to recombine open hardware components (from the UAVP) in a similar way to open source software.