Van Giffen 2.0: naar een nieuwe atlas van de Nederlandse hunebedden

The name Albert Egges van Giffen (1884-1973) is inextricably linked with the Dutch hunebedden (megalithic tombs). This research topic fascinated him even before he established the BiologischArchaeologisch Instituut (BAI, now the GIA, Groninger Instituut voor Archeologie, the department of Archaeology of Groningen University) in 1920, and he continued to study the hunebedden until the end of his life. Apart from hunebed G5-Heveskesklooster, discovered in 1982, there is no megalithic tomb that he didn’t investigate, restore or describe, or for which he didn’t specify the site’s layout. In 1918 the Dutch government asked him to survey the condition of the hunebedden. A few years later his research was to result in his standard work De hunebedden in Nederland, comprising two text volumes and an atlas (1925-1927). The atlas, measuring 51 x 33 cm, contains both photos and drawings of the tombs, the latter in the form of plans with a scale of 1:50. This work turned out to be the last integral overview of the Dutch hunebedden. However, since Van Giffen documented them in 1918, the tombs have undergone numerous minor and major changes during excavations, restorations, repair work and reconstructions. Van Giffen himself was involved in many of those operations, but none, or only very few of the resultant changes were cartographically recorded. In 2016 the Gratama Foundation subsidised a project initiated by the GIA to create a new survey of the Dutch hunebedden based on the use of 3D photography (photogrammetry), GPS and a geographical information system (GIS). In this project the hunebedden were once again recorded in 2D, including all the changes they had undergone in the preceding hundred years, and for the first time also in 3D. In our article we present a survey of the possibilities offered by the photogrammetric models – and the top views and elevation models derived from them – on the basis of a selection of the Dutch hunebedden. The photogrammetric models are not restricted to the hunebed boulders but also include the surrounding area and its (micro)relief. The new elevation models have been linked to absolute elevations and coordinates in the Rijksdriehoekstelsel (the national system for the Netherlands) and are very accurate. Thanks to these models the remains of earthen mounds that once covered the tombs can also be successfully recorded, as we illustrate here in relation to the hunebedden D5-Zeijen and D40-Emmerveld-ZO. The photogrammetric models have also yielded geometrically corrected top views (known as orthophotos) with a very high resolution. By combining Van Giffen’s descriptions and comparing the present situation with that of 1918 we obtain a complete overview of the changes that have taken place in the past hundred years. This we illustrate here in relation to D15-Loon, D16- Balloo, D26-Drouwenerveld, D43-Schimmeres, D45-Emmerdennen, D50-Noord-Sleen-N and D52-Diever. The new data also make it possible to study ‘twin hunebedden’ such as D3 and D4 at Midlaren and D19 and D20 at Drouwen both separately and together. In a few cases the 3D data have led to new insights. For example, we have now been able to prove that the D1 and D2-3 capstones of D29-Buinen-Z were split from the same boulder, as Van Giffen indeed suspected. In making the Van Giffen 2.0 data available we hope that this recording of the situation in 2018 will serve as a reference work for researchers, heritage managers and the public at large.