We tested the use of a low-cost GPS RTK to set up a grid during the intensive archaeological survey of the Piscina Torta site, in the framework of the Salt and Power project of the University of Groningen. We also suggest not using a local grid but the WGS84 UTM grid and naming the single cells with the coordinates of one of its vertices. This would facilitate the use and exchange of the data (e.g. about the potsherds collected in the cell) among the scientific community

Alessandri, Luca

Baiocchi, Valerio

Monti, F.

English

Proceedings - University of Groningen

   University of GroningenIntensive archaeological survey at Piscina TortaAlessandri, Luca; Baiocchi, Valerio; Monti, F.Published in:IMEKO TC-4 International Conference on Metrology for Archaeology and Cultural HeritageDOI:10.21014/tc4-ARC-2022.035IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:2022Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Alessandri, L., Baiocchi, V., & Monti, F. (2022). Intensive archaeological survey at Piscina Torta: use of alow-cost RTK portable kit to materialise a UTM grid on the ground. In IMEKO TC-4 InternationalConference on Metrology for Archaeology and Cultural Heritage (pp. 181-185). IMEKO InternationalMeasurement Confederation. https://doi.org/10.21014/tc4-ARC-2022.035CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 01-02-20242022 IMEKO TC-4 International Conference on Metrology for Archaeology and Cultural Heritage University of Calabria, Italy, October 19-21, 2022  Intensive archaeological survey at Piscina Torta: use of a low-cost RTK portable kit to materialise a UTM grid on the ground L. Alessandri1, V. Baiocchi2, F. Monti2 1 University of Groningen, GIA, Groningen (The Netherlands) - l.alessandri@rug.nl 2 Sapienza University of Rome, DICEA, Rome (Italy) - (valerio.baiocchi, felicia.monti)@uniroma1.it  Abstract – We tested the use of a low-cost GPS RTK to set up a grid during the intensive archaeological survey of the Piscina Torta site, in the framework of the Salt and Power project of the University of Groningen. We also suggest not using a local grid but the WGS84 UTM grid and naming the single cells with the coordinates of one of its vertices. This would facilitate the use and exchange of the data (e.g. about the potsherds collected in the cell) among the scientific community.   I. INTRODUCTION In 1984, G. Pisani Sartorio and S. Quilici Gigli [1] found a huge amount of Iron Age potsherds scattered on a surface of about 10 ha, inside the Natural Park of the Pineta di Castel Fusano, in a locality named Piscina Torta. The potsherds, which can be dated to the VII and VI centuries BCE, all belonged to reddish jars and dolia. This type of vessel is usually associated with some specialised activities like fish processing (sauce, conservation) and/or salt production, possibly through the briquetage technique. The latter is a widespread technique all over Europe [2-4] and consists in boiling brine in a ceramic container (the reddish jars) until the salt (NaCl) precipitates due to the water evaporation. To extract the salt cake breaking the vessel is necessary: this would explain the huge amount of potsherds in those specialised sites [5-7]. Before the archaeological excavation, we decided to collect all the surface artefacts in a grid of 5x5 m. The aims were both to confirm (or modify) the chronology of the site and to obtain data that could guide us in the placement of the subsequent excavation soundings through the study of surface ceramic density. The advantages of reporting absolute geographic positions of archaeological surveys have already been debated and shown in the literature, particularly in the case of underground areas and in urban areas [8-16] here we propose a methodology to trace and materialise the grid for archaeological sites outdoors in open areas.    II. METHODS Only a small portion of the site was surveyed using the grid system (Fig. 1 and 2) due to the vegetation cover. The 5x5m grid was set up using QGIS 3.22 and oriented following the WGS84 UTM 33N datum (EPSG 32633). It was materialised on the ground placing some Master Stakes every 20m on the grid node locations.     Figure 1. Gathering the data: software and hardware  The intermediate stakes were then placed using a measuring tape. To place the Master Stakes we used the ArduSimple RTK Portable Bluetooth Kit coupled with a smartphone Samsung Galaxy A52. We used the free GIS and mobile mapping app SW Maps 2.9.0.3 to process the signal from the free GNSS RTK permanent network of the Regione Lazio and we collect the data using the free mobile platform Epicollect5.  During the survey, 80% of the surface potsherds was collected and put in plastic bags. The code of the plastic bag is the NE corner of the cell from which the potsherds come (Fig. 3).  181To verify the potential of our approach and the limits of the Ardusimple receiver we compared it with a GNSS Geomax Zenith 10 receiver that acquires data from GPS and Glonass constellations in dual frequency by repeating a significant number of nodes of the grid (Fig. 4 and 5).III. RESULTSThe results obtained are surprising, in particular the deviations between the same points measured with the Ardusimple receiver and the Geomax receiver are very small despite the different antenna quality, probably due to the greater number of constellations that the Ardusimple can acquire. For what has been said, and for reasons of space, these results will not be reported in detail; also with regard to the verification of the accuracy of the proposed method, i.e. the deviation between the planned positions of the grid nodes and their actual position in the field re-measured with Ardusimple, the results show maximum deviations of 20 cm (Fig.5).In detail they ranged from a few mm (white or light redtriangles) up to 20 cm (dark red triangles). The remarkable accuracy is probably due to the proximity of the permanent Figure 2. The UTM grid on the archaeological siteFigure 3. Cell code assignment procedure182stations operated by the Lazio Region administration, the flat morphology, but also to the large number of observable satellites. Their layout (still fig. 5) suggests that both the physiological lower accuracy of the points identified with the metric tape and the obstructions of the trees, mainly those to the south, have an influence.    These results on the one hand greatly encourage our proposed procedure and on the other hand draw our attention to the effects of obstructions and vegetation cover.                                 IV. DISCUSSION  The multidisciplinary approach of this contribution has made it possible to study a methodology for the definition of field grids. This approach was made possible by the very recent availability of handheld receivers and smartphones [17] with a significantly smaller footprint and lower cost than 'classical' differential receivers. These new receivers, in turn, benefit from the recent completion of the four major GNSS constellations (particularly Galileo and Beidou), which have only recently made it possible to acquire even at sites where it was until recently impossible to operate with conventional GPS/GNSS receivers. The basic idea is to create filed grids in a plane map reference system such as the UTM that is used worldwide and, for example, can also be set up on the well-known Google Earth platform. The advantages of this approach are mainly two: the geometric correctness of the grid itself in terms of shape and size, and its repeatability. As far as the first aspect is concerned, it is easy to see that points surveyed with receivers that have potentially centimetric accuracies on an absolute grid (such as the UTM grid) will make it possible to obtain a final grid with a much more regular and reliable geometry, making the results statistically much more significant. Furthermore, the possibility of being able to replicate the same grid with no margin of error even years later is of considerable interest. Once again, this allows for greater reliability and significance of the data but also makes it possible to finish and resume the research work without uncertainty even after days or in subsequent campaigns, even years apart.   Figure 5. Absolute deviations of coordinates measured with handheld receiver from integer coordinates of nodes  The proposed methodology does not require every single Figure 4. The survey with the Geomax receiver where the tree cover issue is evident 183node of the grid to be surveyed with the GPS/GNSS receiver, especially if the area is flat as in the case under study, but it may be sufficient to survey a few notable points and from those create the rest of the grid with the measuring tape as is traditionally done. In some cases this methodology, which we could call 'hybrid', is the one we would recommend, not so much for speed (the tested GPS/GNSS receiver, once correctly configured, acquires a point in just a few seconds) but because some nodes often fall in areas with intense tree cover and, in that situation, the GPS/GNSS receiver could give largely erroneous results because of the well-known 'multipath' effect, due to the reflection of the GPS signal on surfaces close to the antenna receiver. In particular, the 'multipath' effect should be greater with 'handheld' receivers that have less shielded antennas, compared to the antennas of (bulkier) professional receivers that have specific shielding. In this regard, it should be remembered that no receiver is however exempt from the risk of 'multipath' and therefore it is always best to consider that a measurement made near obstacles could contain gross errors, whichever receiver is used.  Before the availability on the market of low-cost RTK kits, the grids supporting the archaeological surveys were locally made using a total station. Afterwards, some stakes would have been measured (usually the ones on the corners) to georeference the grid. An expensive GPS and trained people were then needed. The alternative was to use the smartphone built-in GPS with a 20-10 m precision. This usually resulted in a quite imprecise localization of the grids, especially when it is necessary to locate already surveyed cells on the ground again. The availability of very intuitive RTK kits with centimetre accuracy opens interesting new possibilities. The grid can be decided in advance and based on the corresponding national grid or some worldwide datum, like the WGS84. During the survey, the potsherd bags from each cell are named with a code. The latter is usually a consecutive number which is also the name of the cell. Using a code made from the coordinates of the NE corner of each cell (like for example 279977,4621261) would make the content of every single bag “georeferenced” even if the corresponding maps are lost.   REFERENCES   [1] G., Quilici Gigli, “Trovamenti arcaici nel territorio laurentino: annotazioni di topografia e prospettive di ricerca”, Bullettino della Commissione Archeologica Comunale di Roma 89, 1984, 9–26.  [2] A.Harding, “Salt: White Gold in Early Europe, Elements in the Archaeology of Europe”, Cambridge University Press, 2021, Cambridge. https://doi.org/10.1017/9781009038973  [3] A.Harding, “Salt in Prehistoric Europe”,  Sidestone, Leiden, 2013.  [4] O.Weller, R.Brigand, “Archaeology of Salt: approaching an invisible past”, 2015  [5] L.Alessandri, K.F.Achino, P.A.J.Attema, M.de Novaes Nascimento, M.Gatta, M.F.Rolfo, J.Sevink, G.Sottili, W.van Gorp, “Salt or fish (or salted fish)? The Bronze Age specialised sites along the Tyrrhenian coast of Central Italy: New insights from Caprolace settlement”, PLOS ONE 14, 2019. https://doi.org/10.1371/journal.pone.0224435  [6] L.Alessandri, P.Attema, “Dal briquetage alle saline nella protostoria dell’Italia centrale”, 2022, IpoTESI di Preistoria 14, 161–168 https://doi.org/10.6092/issn.1974-7985/14338 [7] J.Sevink, W.De Neef, L.Alessandri, R.van Hall, B.Ullrich, P.A.J.,Attema, “Protohistoric briquetage at Puntone (Tuscany, Italy): principles and processes of an industry, based on the leaching of saline lagoonal sediments”, Geoarchaeology, 2020 https://doi.org/10.1002/gea.21820  [8] V.Baiocchi, R.Brigante, S.Del Pizzo, F.Giannone, M.Onori, F.Radicioni, A.Stoppini, G.Tosi, S.Troisi, M. Baumgartner, “Integrated geomatic techniques for georeferencing and reconstructing the position of underground archaeological sites: the case study of the Augustus Sundial (Rome)”, Remote Sens. 2020, 12, 4064. DOI: 10.3390/rs12244064  [9] F.Radicioni, P.Matracchi, R.Brigante, A.Brozzi, M.Cecconi, A.Stoppini, G.Tosi, “The Tempio Della Consolazione in Todi: Integrated Geomatic Techniques for a Monument Description Including Structural Damage Evolution in Time”, International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives, 42(5W1), 2017, 433–440. DOI: 10.5194/isprs-Archives-XLII-5-W1-433-2017  [10] L.Alessandri, V.Baiocchi, S.Del Pizzo, F.Di Ciaccio, M.Onori, M.F.Rolfo, S.Troisi, “Three-dimensional survey of Guattari cave with traditional and mobile phone cameras”, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci. XLII-2/W11, 2019, 37-41.  [11] D.Dominici, E.Rosciano, M.Alicandro, M.Elaiopoulos, S.Trigliozzi, V.Massimi, “Cultural  184heritage documentation using geomatic techniques: Case study: San Basilio's monastery, L'Aquila”, Digital Heritage International Congress (DigitalHeritage), 2013, pp. 211-214.  [12] L.Alessandri, V.Baiocchi, S.Del Pizzo, F.Di Ciaccio, M.Onori, M.F.Rolfo, S.Troisi, “A flexible and swift approach for 3D image–based survey in a cave”, Appl Geomat 14 (Suppl 1), 2022, 5–19  https://doi.org/10.1007/s12518-020-00309-4  [13]  A.Masiero, F.Fissore, M.Piragnolo, A.Guarnieri, F.Pirotti, A.Vettore, “Initial evaluation of 3d reconstruction of close objects with smartphone stereo vision”, Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLII-1, 2018, 289–293. DOI: 10.5194/isprs-archives-XLII-1-289-2018  [14] L.Alessandri, V.Baiocchi, S.Del Pizzo, M.F.Rolfo, S.Troisi, “Photogrammetric survey with fisheye lens for the characterization of the La Sassa cave”, The International Archive of Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W9, 2019, 25–32. https://doi.org/10.5194/isprs-archives-XLII-2-W9-25-2019  [15] D.Costantino, M.Pepe, A.G.Restuccia, “Scan-to-HBIM for Conservation and Preservation of Cultural Heritage Building: The Case Study of San Nicola in Montedoro Church (Italy)”, Applied Geomatics, 2021. DOI 10.1007/s12518-021-00359-2   [16] L.Alessandri, G.L.Cardello, P.A.J.Attema, V.Baiocchi, F.De Angelis, S.Del Pizzo, F.Di Ciaccio, A.Fiorillo, M.Gatta, F.Monti, M.Onori, M.F.Rolfo, M.Romboni, G.Sottili, S.Troisi, “Reconstructing the Late Pleistocene – Anthropocene interaction between the neotectonic and archaeological landscape evolution in the Apennines (La Sassa cave, Italy)”, Quaternary Science Reviews, Volume 265, 2021, 107067, ISSN 0277-3791, https://doi.org/10.1016/j.quascirev.2021.107067.  [17] U.Robustelli, V.Baiocchi, L.Marconi, F.Radicioni, G.Pugliano, “Precise point positioning with single and dual-frequency multi-GNSS android smartphones”, CEUR Workshop Proceedings, 2020   185

Intensive archaeological survey at Piscina Torta:use of a low-cost RTK portable kit to materialise a UTM grid on the ground

https://pure.rug.nl/ws/files/854169148/IMEKO-TC4-MetroArchaeo2022-035.pdf

Intensive archaeological survey at Piscina Torta:use of a low-cost RTK portable kit to materialise a UTM grid on the ground

Abstract

Similar works

Full text

Available Versions

Proceedings - University of Groningen