Monday, 8 August 2016

Kinect, a sleeping research branch reacivated

As you probably noticed, one of the topic of ATOR is related with hardware hacking, with the aim to build new archaeological devices from ordinary objects and tools (33).
This concept is close to the one of "reuse" (using an artefact for a purpose which is completely different from the original function), a pretty common phenomenon in archaeology; also in architecture there is something similar,  called "spolia" (but maybe our interest in hacking things is just a kind of McGiver syndrome of people grown up in the 80s).
However, this post is about hacking a common game device like Kinect to use its characteristic in archaeological 3D real-time documentation. If you are a regular reader of ATOR, you will know that we already face this challenge, performing a first test (1) with RGBDemo in February 2012, and controlling accuracy and precision of the device in March of the same year (2), after a discussion with some of the researchers of FBK, during the workshop "Low cost 3D: sensori algoriti e applicazioni". Due to the encouraging results achieved in our first experiments, we worked on the hardware in order to modify it for outdoor projects (3), but soon we experimented the limits of this technology when applied in areas with direct sunlight (4) or in documenting small objects (5, 25). Despite this drawbacks in our research, Kinect worked pretty good in indoor excavations (6), helping us in difficult situations (related with the the workplace safety), and for particular purposed, like for infra-red prospections in dark environment (7).
After all these experiences, our final advice about Kinect is that the device has a potential in archaeology, but its real employment in professional work is restricted to peculiar conditions, while in most of the cases the SfM-based techniques are the best option (due to their versatility, which makes them a perfect choice during missions abroad (8), for small finds documentation (9, 10), for underwater and aerial archaeology (11, 12, 13), considering also the speed which characterize SfM and MVSR open source software development (14) and the wide range of possibilities between the different tools (15, 16).
Well, at least this was our opinion until now... Currently we are changing our mind about Kinect, and this is due to our professional engagement in underground archaeology (17) and to our renovate interest in robotics. Let's deal with these two points separately.

Underground archaeology

Documenting an underground semisubmerged structure in Firuzabad (Iran)

Like any other operation in archaeological 3D documentation, the tolerance regarding accuracy and precision is variable and influenced by some factors, and mainly: research purposes, logistics, characteristics of the structures to be documented.
Without considering some important exceptions (e.g prehistoric rock shelter, which are often simple to document with SfM techniques), most of the structures related with underground archaeology (WW1 artificial caves, medieval mines, etc...) are connected with large scale survey projects (where it is important a "big data" approach, raising the tolerance in data acquisition to increase the number of documented structures); with logistically difficult areas (high mountains, glaciers, (18, 19) etc...); with structures often characterized by vast surfaces without important small details, which (when present) can be recorded with a targeted SfM or RTI (21, 22) documentation (e.g. for graffiti, inscriptions (20), manufacture traces, etc...). For this reason, in most of these projects, it is necessary to deal with precision in documenting (keeping checkpoints thanks to other TOF instruments, like total stations) in order to gain a real-time response from the selected device, and, under this point of view, Kinect is often a good solution, considering also that its infrared sensor helps very much in low light conditions (7).

Documenting WW1 caves in Southtirol (Italy)

Archeorobotics

Arc-Team's UAV during an aerial archaeology project in Storo (Trentino - Italy)

Since 2006, when we joined an aerial archaeological project in Armenia (23), we started to work on "archaeorobotics", trying to develop robotic devices able to help us in the most difficult archaeological missions.
The first positive results we reached in this field were related with aerial archaeology and the building of an open hardware UAV (in 2008), even if at the beginning we underestimated the time needed to practice with our new tool  (24). Soon our experience increased as we built different drones, based on open and closed solutions (like kk multicopter (26) or Naza dji (27) models). The benefits of this research branch were clear (28, 29) and soon other research institutions, like the CNR-ITAB of Rome (30), the University of Lund (31) and  the CNR-ISTI of Pisa (32), asked us to give lessons about this topic.
Another field of archaeorobotics we explored is the one related with CNC machines and especially with 3D Printers. For this topic a precious help came from the society Kentstrapper and Leonardo Zampi (aka +Exekias 87), who helped us in 3D printing the cast of the Taung Child (34, 35). Since RepRap project started (in 2005), 3D printers evolved very fast. Of course our interest regarding these machines is mainly oriented to Cultural Heritage, and this is also the reason why we built a Fa)(a 3D form scratch (36), but results with this kind of instruments can be very impressive, especially considering the wide range of scientific applications (37, 38, 39, 40, 41), even if sometimes you have to deal with difficult boolean operations (42).
However, none of the robotic projects we developed till now needed Kinect, being based on UAV, to 3D document archaeological sites, or on CNC machines, to fast replicate archaeological artefacts. Our renovate interest in Kinect for archeorobotics is due to our new challenge in developing a ROV (Remotely Operated Vehicle), in order to assist us in our underwater archaeological missions. Indeed, in the last months, we started a collaboration with the WitLab, the FabLab of Rovereto (Trentino - Italy), to develop a new Open Hardware ROV, especially designed for archaeological aims. One of the main topic in developing such an instrument is that the new robot will be oriented not only to 3D documentation, but also to the exploration of unknown areas. For such reason SfM and MVS software are no more enough, but we had to start again in testing Open Source SLAM (Simultaneous  Localization And Mapping) algorithms, due to the fact that we need to register in 3D the submerged landscape (Mapping), but also to recover the path the "ArcheoROV" did (Localization) to reach new hidden archaeological evidences (for a better planning of human operations).

Testing the ArcheoROV at night


Testing Open Source SLAM solutions

The importance of SLAM algorithms in exploring devices is the main reason why we started again to experiment Kinect. Indeed, despite Kinect cannot be used as an on-board optical device in our ArcheoROV (due to the infrared camera), this tool is the perfect system to check SLAM software.
If, you ever started in working on robotics, probably sooner or later you stepped into ROS (Robot Operating System), an Open Source (BSD License) collection of software frameworks for robots. Of course SLAM is a very important task for any robotic vehicle, and the ROS package RTAB-Map is a perfect solution to implement this capability into any autonomous or remotely operated machine, like our ArcheoROV. For this reason, before starting experiments in more sophisticated (and complicated) systems, we checked RTAB-Map performance with an old Kinect, and here is the video of the result:



As you can see, the performance of real-time 3D is pretty responsive, respect our old experiments with the Open Source software RGBDemo (also considering that the Kinect used in this video is the first version, and it is now pretty obsolete) and, most important, the localization function within SLAM algorithm works very good. As I wrote at the beginning of the post, our current impression is that this combination of hardware (Kinect) and software (ROS) can be a good solution for underground environment documentation, while the software can be the right choice for archaeological exploring robotic devices.

I hope that this long post will be useful, if you have any feedback, please just write your comment below. Have a nice day!

PS:

we will present the ArcheoROV at the ArcheoFOSS (43) of Cagliari (Sardinia - Italy), this year. Also our partner of WitLab will be with us!

Webography

ATOR:

(1) Kinect, real-time 3D; (2) Kinect accuracy and precision with RGBDemo; (3) Kinect 3D outdoor: hacking the hardware; (4) Kinect 3D outdoor: first test; (5) Kinect 3D limits: documenting small objects; Kinect 3D indoor: excavation test (6); Kinect - Infrared prospections (7); Aramus 2014: 2D and 3D documentation of archaeological excavation (8); 3D for archaeological finds (9); Taung Project: 3D with SfM & IBM (10); Extreme SfM: underwater archaeology (11); From drone-aerial pictures to DEM and ORTHOPHOTO: the case of Caldonazzo's castle (12); Documentation of a bas-relief on a cliff : the workflow (13); CMVS/PMVS2 40% faster (14); OpenMVG VS PPT (15); MicMac and PPT: two FLOSS solutions for 3D data (16); SfM for Underground Documentation (17); Archaeology as a profession (18); Glacial Archaeology: About the challange to work in extreme conditions (19); WW1: High Alpine Survey Data - Work in Progress (20); Arc-Team tries Large Scale Reflectance Transformation Imaging (RTI) (21); WebRTIViewer (22); UAVP (Universal Aerial Video Platform) (23); UAVP indoor flight (24); 3D documentation of small archaeological finds (25); Building an Xcopter (26); Arc-Team's UAVP: testing the NAZA dji (27); Xcopter drone and SFM techniques (28); ArcheOS and UAVP for archaeological remote sensing (29); Open Source Remote Sensing Platform (30); Remote sensing with UAV in archeology (lessons at Lund University) (31); Aerial archaeology with FLOS Hardware and Software (32); A DIY endoscope for emergencies during excavation fieldwork (33); 3D PRINTING THE PAST: SOME ISSUES (34); The Taung Child is now touchable, thanks to 3d printing (35); 3D printing for Cultural Heritage (36); Space archaeology (37); 3D PRINTING GOOGLE MAPS IS NOW EASY (38); When Veterinary Medicine and 3D printing meet each other (39); Three more animals are saved with the aid of Blender and 3D printing (40); Augmented Reality at Cultways (41); Boolean operations - the powerful Cork! (42); ArcheoFOSS 2016 in cagliari! (43)

Kentstrapper website: http://kentstrapper.com/

Fa)(a 3D website: http://www.falla3d.com/

WitLab website: http://www.witlab.io/

ROS website: http://www.ros.org/

RTAB-Map website: http://introlab.github.io/rtabmap/

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