Geological maps, produced by the Intituto Geológico Mineiro (IGM), were obtained from the Departamento de Geologia, Instituto Nacional de Engenharia, Tecnologia e Inovacão (INETI) at a national scale of 1:200,000 meters. Regional scale geological maps (1:50,000 meter) were obtained but are only available for approximately half of the study region. Topographic maps at 1:25,000 meter scale covering the entire region were obtained from the Instituto Geográfico do Exercito (IGeoE). Aerial photographs were consulted online via the Centro Nacional de Informação Geográfica (CNIG; now SNIG) website.

A systematic, stratified survey was undertaken during the summer months from 2005 to 2008. Survey strata include: 

1. All river terraces along the Sado and its major tributaries; 
2. A series of small bodies of water (“lagoas” and “lagoinhas”) mapped or visible in aerial photographs in the planalto southwest of Grândola; 
3. Jasper outcrops and other potential sources of raw material in primary position.

Survey members worked in teams of 3-5, walking parallel transects approximately 5 meters apart, equipped with WAAS enabled GPS units (Garmin© eTrek).  Tracks were automatically recorded and archaeological finds individually recorded as waypoints and collected. The GPS data were uploaded to a laptop at the end of each day and MapSource© used to post-process the information. Tracks and waypoints were retained, recording the distances covered by each operator and the location of archaeological materials. These data were then saved in a format compatible with ArcGIS 9.2 (ESRI ©) before being uploaded to the GIS. The data were merged by survey area and projected onto digitally stored topographic maps to visually check the day’s work. This ensured that survey intensity and coverage, as well as the number and location of artefacts and their relative density could be calculated.

Archaeological testing

Field testing (sondages) was conducted in 2006 and 2007 at four of the most promising locations (Mina do Paços, Gasparoes, Moinhos II and Vermelha). Excavation revealed that the archaelogical remains lie within the modern plough zone (less than 40 cm below the current soil surface). Below the plough zone, artefacts counts drop dramatically or cease altogether.