beyond the academic – photo modeling applied to complex commercial archaeology
DESCRIPTION
This poster demonstrates the application of photo modelling techniques within the work carried out by MOLA. It shows the technique's application to the recording of excavations and historic buildings, and focus on how it enabled us to overcome some of the problems habitually faced on pressurized commercial projects. It aims to demonstrate the benefits both in terms of time and costs, which its use can deliver. It is a crucial aspect, since if the application of such techniques by the commercial sector can be demonstrated in a cost effective manner, then they have the potential to impact on most of the archaeological investigation carried out within Western Europe.TRANSCRIPT
Beyond the Academic – Photo Modeling Applied to Complex Commercial Archaeology
Moisés Hernández Cordero, MOLA [[email protected]], Azizul Karim, MOLA [[email protected]], Peter Rauxloh MOLA [[email protected]]
Introduction This is to demonstrate the application of photo modeling techniques within the work carried out by MOLA, one of the worlds largest commercial archaeological firms. It shows the technique's application to the recording of excavations and historic buildings, and focus on how it enabled us to overcome some of the problems habitually faced on pressurized commercial projects. It aims to demonstrate the benefits both in terms of time and costs, which it's use can deliver. It is a crucial aspect, since if the application of such techniques by the commercial sector can be demonstrated in a cost effective manner, then they have the potential to impact on most of the archaeological investigation carried out
Historic Building Recording Historic building recording is one of the most important aspects of commercial archaeology in Western Europe. High quality and efficient recording of historic buildings and structures, listed buildings and monuments within a very short time frame is the key. Furthermore due to the immense competition in the sector keeping survey expense an absolute minimum is painfully essential. Being one of the largest commercial archaeology firms in the UK, MOLA started to employ 3D photogrammetry alongside conventional recording methods from spring 2013. The result so far is beyond expectation and MOLA is now confidently using the technique on high profile building recording projects.
within Western Europe. 3500
Archaeological Survey 3000
2500
Point Cloud generated by Photogammetry.
2000
1500
1000
500
0
Time (min) Cost (£)
stone-by-stone
drawing generated from orthophoto produced by 3D Photogrammetry.
Laser Scan Low Cost Photogrammetry
Cost/Resources Close range photogrammetry
compared with the resources used by LaserScan Technique during a survey of a section of the London City Wall.
“Close range Photogrammetry method is one of the most precise, reliable, economic and rapid methods that is currently available”. (2012 Şanlıoğlu et all).
The simplicity and speed of 3D photogrammetry recording on-site, meant that highly detailed records were achieved in a very limited timespan, which could not be done using conventional methods.
Orthophoto created
from point cloud data.
Cross sections
created from slicing 3D model.
Accuracy. “PhotoScan result has more or less the same overall accuracy as the Terrestrial Laser Scanning data set”. (Doneus et alii, 2011: 84) However, “the best results can be obtained by combining the mentioned advantages of both methods. However, the decision for a combination or a single method depends on the aim of the data acquisition and the application behind”. (Grussenmeyer et al, 2008:217)
Comparing Intensity Values RGB values
Plan of the Ice-well base created from orthophoto
Survey approach from close range photogrammetry point cloud 3D model created after removal of the structure. Accuracy of the point cloud match data captured by the Total Station.
Landscape survey and DEM generation
Image 0.5m resolution LiDAR based DTM of a grassed parkland landscape.
Image generated using Agisoft Photoscan from SUA (small unmanned aircraft) imagery. SUA based terrain models are a highly cost effective, and reactive means of capturing such data with a much higher resolution as a default.
walls truncation drains trench
Physical constraints on site meant that rectified photography and total station surveying were impossible. The use of 3D photogrammetry meant that a rectified image and an accurate measured survey could be achieved within budget as required.
GIS processing of SUA based IR imagery allows the production of Normalized Difference Vegetation Indices (NDVI). These are useful for identifying buried archaeological features when their presence causes overlying vegetation to thrive or be under strain. Based on a processing of both visible and Near Infra-red spectrum data, the technique makes explicit relatively small difference in chlorophyll levels, due to the there being much more reflected radiation in the NIR wavelength that visible ones.
Rectified
elevation
photo
Scaffolding removed from point cloud
REFERENCES
Şanlıoğlu, I., Zeybek, M., Karauğuz, G. 2012. Photogrammetric survey and 3D modelling of Ivriz rock relief in Late Hittite Era. Mediterranean Archaeology and Archaeometry, Vol. 13, No 2, pp. 147-157 Doneus, M., Verhoeven, G., Fera, M., Briese, Ch., Kucera, K. and Neubauer, 2011W. From deposit to point cloud – a study of low-cost computer vision approaches for the straightforward documentation of archaeological excavations. Geoinformatics CTU. Praga Pp. 81-88.
Grussenmeyer, P., Landes, T., Voegtle, T., Ringle, K. 2008. Comparison methods of terrestrial laser scanning, photogrammetry and tacheometry data for recording of cultural heritage buildings. In: the XXIth ISPRS Congress, Beijing, China, 3-11 July 2008, Int. Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences, 213–218
* MOLA 3D Photogrammetry processed with Agisoft Photoscan Professional Edition
MOLA (Museum of London Archaeology)
www.mola.org.uk
+44 (0)20 7410 2200
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