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AUTOMATED DATA COLLECTION AND 3D MODELLING OF ARCHAEOLOGICAL SITES: EXAMINING THE PREHISTORY AND

DESTRUCTION OF GRAND BAY IN CARRIACOU

Michiel Kappers, Scott Fitzpatrick and Quetta Kaye__________________________________________________________________________

In the summer of 2005 we completed the second field season of a long-term archaeological project at the Grand Bay site on the island of Carriacou, West Indies. The excavation, led by an international team of researchersfrom England, The Netherlands, and the United States, revealed intensive prehistoric habitation spanning theearly to late ceramic periods (ca. A.D. 400 – 1250) Unfortunately, the site has been and is continuing to beseverely impacted by a host of natural and cultural processes which have led to massive erosion and atremendous loss of cultural remains. In this paper we discuss our efforts to record this rapidly disappearing siteby coupling aerial photographs with highly accurate survey techniques (GPS and Total Station), large scalearea excavation, and a fully automated barcode based computer system to efficiently store, process, and retrievefield data. The resulting GIS dataset has helped to determine levels of erosion in the area and provided themeans to construct 3D modeling of the site, a necessary component for developing future strategies dedicatedto investigating and protecting archaeological sites on the island.

En el verano de 2.005 completamos la segunda sesión de campo de un proyecto arqueológico a largo plazo enel sitio Grand Bay en la isla de Carriacou, Antillas. La excavación, dirigida por un equipo internacional deinvestigadores de Inglaterra, los Países Bajos, y los Estados Unidos, reveló una habitabilidad prehistóricaintensa que abarca desde los periodos cerámicos tempranos hasta los tardíos (ca. 400-1.250 D.C.).Desgraciadamente, el sitio ha estado y está siendo severamente afectado por un sinfín de procesos naturales yculturales que han causado una erosión masiva y una pérdida tremenda de restos culturales. En esta ponenciaexponemos nuestros esfuerzos para registrar este sitio que está desapareciendo rápidamente juntandofotografías aéreas con técnicas de estudio muy exactas (SPG y Estación Total), una excavación del área a granescala, y un sistema computacional enteramente automatizado para guardar eficazmente, procesar, y recuperarlos datos de campo. El grupo de datos del SIG resultante ha ayudado a determinar los niveles de erosión en elárea y proporcionó los medios para construir un modelo en 3D del sitio, componente necesario para eldesarrollo de estrategias futuras dedicadas a la investigación y protecciónde sitios arqueológicos en la isla.

En Eté 2005, nous avons conclu la deuxième étude sur le terrain d’un projet archéologique à long terme sur lesite de Grand Bay sur l’île de Carriacou, aux Antilles. Les fouilles qui étaient réalisées par une équipeinternationale de chercheurs d’Angleterre, des Pays-Bas, et des Etats-Unis, ont révélé une occupationpréhistorique intensive allant des périodes céramiques anciennes aux récentes (environ 400 -1250 a.p. JC).Malheureusement le site a souffert et continue de souffrir d’une multitude de procédés naturels et culturels quiont mené à une érosion massive et une perte considérable de restes culturels. Dans cette communication nousparlons de nos efforts pour archiver ce site qui est en rapide disparition en associant des photographiesaériennes à hautes techniques précises de sondage (GPS et Total Station), une zone de fouille à grande échelle,et un système informatique de codebarre entièrement automatisé pour stoker, reproduire, et rechercher lesdonnées sur le terrain. Le résultat de l’ensemble des données du Système d’Information Géographique (GIS) aaidé à déterminer les niveaux de l’érosion dans la zone et donne l’occasion de construire un modèle 3D du site,un élément utile pour développer des stratégies futures vouées à étudier et protéger les sites archéologiques sur l’île.__________________________________________________________________________

Introduction

In 2003 we began a multinational cooperative research programme on the island of Carriacouin the southern Grenadines. After an island wide survey that same year in which we identified a dozen locations with evidence for prehistoric settlement, we initiated the first

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archaeological excavation campaign at the Grand Bay site in 2004 and continued our workfor two months in 2005.

Our goals for the project include: 1) surveying and recording prehistoric sites on theisland; 2) excavating those sites which have good evidence for long term habitation; 3)examining ways to better preserve and protect the island’s cultural heritage; and 4) usingsophisticated measurement devices and data recording procedures to ensure that the work isdone accurately, efficiently, and with an interface that allows the seamless transfer of spatialand visual data into a Geographic Information System (GIS) programme. Our paper herefocuses on the last of these goals, although we refer to other issues which are integral to theproject.

Background

Carriacou is located in the southern Caribbean and is the largest of the islands found in theGrenadines between St. Vincent and Grenada. Carriacou is politically part of Grenada alongwith Petite Martinique and several smaller islands. The island is approximately 32 squarekilometres in area with a population of around 5,000 people. Geologically, Carriacou iscomposed of a mixture of volcanic lava and Miocene-aged fossiliferous limestone (Pickerallet al. 2001, 2002; Donovan et al. 2003) that reach heights of up to 290 m in both the island’snorthern and southern half.

Our archaeological field programme on Carriacou began in 2003 with a two weeksurvey that covered most of the island’s coastline and accessible parts of the interior.Previous visits to the island by researchers revealed a number of important sites along thecoastline (Bullen and Bullen 1972; Sutty 1990), but no prior systematic survey had beencarried out. The goal of this project was to discover and examine site locations, determinewhich had the highest potential to reveal subsurface cultural remains, and assess the threat ofdestruction to sites by natural erosion, looting, and development (Kaye 2003:129–135; Kayeet al 2005:391–398). The survey campaign examined several previously known locations andrecorded a number of other prehistoric sites. These locations ranged from very sparse remainsof artefacts on completely eroded and/or destroyed areas to very rich and dense sites foundprimarily on the eastern coast.

Grand Bay

The Grand Bay site is located in the largest bay on the island that stretches for about 2,500meters along the eastern coast. The coral reef system that fringes the island, sits furtheroffshore here, approximately 1,500 to 2,500 meters away. The exact dimensions of the sitehave not yet been fully determined due to heavy vegetation growth, but it clearly extends for130 meters along the coast and between 30 to 60 meters inland.

The site is archaeologically rich with dense midden material dating from ca. AD 350–1250 (Fitzpatrick and Kappers n.d.). Archaeological finds thus far include human burials,posthole features, a wide array of ceramics and artefacts made from stone, shell, bone, and aplethora of food remains. Preliminary zooarchaeological analysis indicates that Grand Baymidden deposits contain a variety of fish and shellfish remains commonly found in otherprehistoric sites in the Caribbean, but also agouti, opossum, iguana, land crab, sea urchin, andsignificant amounts of turtle (LeFebvre 2005).

Due to heavy erosion, large amounts of material have come to the surface and isconstantly being washed away by wave and storm action and sand mining. Erosion has

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encouraged looting at the site and all of these processes have made the site extremelyvulnerable to destruction. Based on our conversations with local landowners, photographs,and detailed measurements of the site boundaries over the past few years, we estimate that the site is eroding at an average rate of 1 m per year (Fitzpatrick et al. n.d.).

Although erosion and looting have caused the site to degrade considerably, the profilenonetheless provides great insight into how the site formed over time. Several distinct middenlayers are clearly visible above the sterile subsoil and the lower parts of features such aspostholes can be clearly seen. As such, the Grand Bay site can be divided into two maincomponents: a dark brown to black midden layer containing large amounts of archaeologicalmaterial that rests atop a yellowish/light brown subsoil.

Midden layers consist of an accumulation of material deposited over a 1,000 yearperiod. During this time, different periods of occupation have led to the overlap andadmixture of cultural remains. Postholes from early house construction, for example, mightbe found under later midden deposits and later house plans cut through midden deposits ofearlier phases. Post-depositional processes such as bioturbation and erosion further serve tomix material from different phases and complicate interpretation, especially of shorteroccupational periods.

Field Methodology

Because of the nature of soil deposits at Grand Bay, each component demands its owndistinct methodological approach. In order to prevent added stress to the site which couldaccelerate erosion, we worked to avoid excavating large east-west trenches. We insteadalternated 5x5 m excavation units which were set out from a baseline between two pointsusing a Sokkia Total Station and measured by GPS to anchor our grid to the local Grenadacoordinate system. The numbering of the units was arranged so that the site could beextended in all directions, if necessary. This strategy allows us to create extendedstratigraphic profiles without fully excavating one long contiguous trench (Figure 1 inset).

Two 5x5 m trenches (446 and 415) were chosen to begin excavation of the middencomponent. Three other trenches (561, 592, 563) were opened along the edge of the heavilyeroded surface area which had less occupation refuse, but greater potential for discoveringhousehold features.

The 5x5 m trenches were further subdivided into 1x1 meter squares and excavated in10 cm arbitrary levels. The 25 1x1 m squares were marked with survey pins and numberedsequentially (beginning in the SW corner) from 1–25. All are excavated using trowels,shovels, and/or mattocks with the exception of four center squares (7, 9, 17, 19) which arewet screened over 6 mm (¼”) mesh. In addition, a 50x50 cm column samples were takenfrom the SW corner of each sample square and wet screened over 6 mm (1/4”) mesh first and then 1.5 mm (1/16”) to recover smaller site constituents.

Before a level in a unit is excavated, each square receives a barcode label on the SWcorner pin and respective depths are measured with the Total Station. We can then obtain 3Dmeasurements of squares, enabling us to reconstruct the shape and location of the units andmore accurately record all material found within each square. This also makes it possible tosearch for any possible vertical dispersion patterns of cultural remains (Figure 2).

In more eroded areas where the subsoil was exposed, for example in Trench 592, wescraped the surface and recorded all features found within including postholes and burials.We created surface drawings showing the visible features which were digitized and placedinto our own MapInfo GIS to create a feature plan. Larger postholes often contained refusematerial such as stones, coral, rock, pottery, and bone as a foundation for the post. The

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burials were situated on the elevated portions of the site with bones protruding through thesurface (see Figure 1).

After the surface drawing was finished, all non-burial features were sectioned and drawn. Burials where excavated in horizontal levels and four iron nails put on the corners of an imaginary rectangle around the burial. These nails were then measured to obtain their 3Dcoordinates and digitally photographed. This enabled us to georeference the digital photos ina GIS and digitize (vectorize) the remains.

Data Processing

To measure and record excavation procedures, archaeological material recovery, featuredistribution, and site formation processes more accurately, we took several thousandmeasurements using a Total Station. We were particularly interested in detailing the extent towhich the site formed and changed over time as a result of both prehistoric, natural, andmodern processes. Recording of the site nearly every year using photographic and varioussurvey techniques helped us to determine the rate of erosion and together with aerialphotographs from the last few decades and the use of GPS and GIS, we are reconstructingGrand Bay’s original size and estimating the long-term destruction to the site.

Another critical part in compiling data for the site is the use of a computerised datasystem and barcode labels. Our data storage and retrieval system is specifically designed tocollect, store, and retrieve vast amounts of data quickly and efficiently. The system isstructured so that we can quickly enter data both in the field and the laboratory – the use ofbarcodes significantly speeds up the processing work (Figure 3) The system also usesautomatic digital scales that are connected with the system to seamlessly transfer the weightsof finds into the database.

The database system module for field and finds processing is now being used in ourexcavation at Grand Bay and in excavations in The Netherlands. It comprises a standardisedhierarchically arranged database and complies with all of the necessary criteria to meet thestandards of a technically correct database (Kappers and Haanen 2001). A second moduleused to store and retrieve image data such as field and find photographs and drawings isnearly finished. This module will be fully integrated into the dataset and connect all imagedata relevant to a particular site context and will be automatically stored during the field andfind processing work. A third module will have a fully integrated and format independentGIS, connected to the same base dataset, which will allow onsite data retrieval, processing,and map construction in real time.

Find Numbering

The find number is the basic entry type in the data system. Every item that is excavated orretrieved in the field receives a unique find number. This find number is printed on thebarcode label and usually pre-printed in batches. The find number starts at 1 and continues upto the last number needed. The find numbers at Grand Bay include the year of the campaign(04/05) followed by the three letter code for the site name (CGB to represent CarriacouGrand Bay) and a 6 digit unique number starting at “000001.” When a find number isassigned it is simultaneously written either on a paper form or entered directly into the datasystem using a touch screen computer in the field, for example (Figure 3). At this stage, allprovenience information is entered and forms the basis for information assigned in the field.

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When find bags arrive at the processing location, the finds are washed, dried, andsorted into categories. The material from each category is placed into a separate bag.Different bags containing a single category of material (e.g., pottery) are then put together ina larger bag (or a different type of container depending on weight of finds, etc.) accompaniedby the original barcode label assigned in the field. The field information is then entered intothe database system (Figure 4a shows the accompanying configuration) and the packagepassed to the finds processing manager who weighs the bags. Depending on time or the typeof analysis, the processor may count the finds and also store that information in the datasystem. At this stage, a new barcode label is printed automatically. The sample number isextended with the category code and a possible sub-number (Figure 4b).

All boxes used to store material have a barcode and that information is stored in thedata system to relocate particular bags (Figure 4c). The system also provides the option tostore information about material that has been sent to a specialist, any analytical results, andwhen remains should be returned to the prospective museum, agency, or individual whooversees the management of archaeologically recovered material.

Conclusions

The results of the Grand Bay archaeological field project have thus far revealed a number ofimportant finds ranging from household structures, human burials, midden refuse, and avariety of unique and important artefacts. Our ability to systematically excavate the site using advanced survey and recording technologies, including a newly developed and customizabledatabase system, has enabled us to efficiently and accurately recreate our excavationprocedures, analyse these findings as we progress with fieldwork activities, and interpret allsite finds in ways that are not possible with more conventional excavation procedures. Thishas allowed us to gain a better understanding of how the Grand Bay site formed over timeand is currently changing as a result of both human and naturally caused phenomena. Ourstrategy of combining computer-aided finds processing and on-site mapping, along with alaboratory protocol that takes advantage of a barcode labelling system, provides a strongfoundation for easily retrieving information already collected, seamlessly connecting largetabular, spatial, and photographic datasets, and viewing patterns of past human behaviour in a GIS that would otherwise not have been possible.

References Cited

Bullen, Ripley P., and Adelaide Bullen 1972 Archaeological Investigations on St. Vincent and the Grenadines, West Indies.

William Bryant Foundation, American Studies, Report No. 8. Fitzpatrick, Scott M., and Michiel Kappers

n.d. Strong Evidence for a Intensive Late Ceramic Period Occupation in theSouthern West Indies. Submitted for publication.

Fitzpatrick, Scott M., Michiel Kappers, and Quetta Kaye n.d. Coastal Erosion and the Destruction of the Grand Bay Site on Carriacou,

Southern Lesser Antilles. Submitted for publication.Kappers, Michiel, and Paul L.P. Haanen

2001 Structured Data Storage and Retrieval within Caribbean Archaeology.Proceedings of the XIX International Congress for Caribbean Archaeology.Volume I, edited by Luc Alofs and Raymundo A.C.F. Dijkhoff, pp. 66–76.Publications of the Archaeological Museum Aruba 9, Oranjestad, Aruba.

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Kaye, Quetta 2003 A Field Survey of the Island of Carriacou, West Indies, March 2003. Papers

from the Institute of Archaeology 14, pp. 129–135. Kaye, Quetta, Michiel Kappers, and Scott M. Fitzpatrick

2005 Archaeological Survey of Carriacou, West Indies. Proceedings of the XXInternational Congress for Caribbean Archaeology, pp. 391–398. SantoDomingo, Dominican Republic.

LeFebvre, Michelle J. 2005. Prehistoric Exploitation of Vertebrates at the Grand Bay Site, Carriacou, West

Indies. Paper presented at the 21st Congress of the International Association ofCaribbean Archaeology, July 24–30, Trinidad West Indies.

Sutty, Leslie1990 Listing of Amerindian Settlements on the Island of Carriacou in the Southern

Grenadines and a Report on the Most Important of These, Grand Bay.Proceedings of the 11th Congress of the International Association forCaribbean Archaeology, pp. 242–259, Puerto Rico.

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List of Figures

1. Map of central portion of the Grand Bay site.

2. Hypothetical schematic of layers and site constituents.

3. A Fujitsu Tablet PC encased in an environmentally protective Otterbox case. Note barcode scanner and label on bottom right.

4. Screenshots of database system.

Figures

Figure 1

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Figure 2

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Figure 3

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Figure 4