Usability of LiDAR for detecting and measuring archaeological structures in Northern Norway

In cooperation with the national and regional Norwegian and indigenous Sami cultural heritage authorities, the Norwegian Institute for Cultural Heritage Research (NIKU) has investigated the usability of LiDAR for detecting cultural heritage in northern landscapes. An area of 31.5 square kilometres was laser scanned in Tana and Nesseby 500 kilometres north of the Arctic circle.

The study area is an Arctic landscape of soft hills covered by low vegetation and partly covered by mountain birch forest. The soft shape of the landscape and open vegetation is suitable for providing good quality LiDAR data. The density of points captured was 5 - 8 point/m2 and average point density used to create the DTM (Digital Terrain Model) was 3 point/m2. The digital model was analysed manually and all structures interpreted as cultural remains marked and later looked up in the field.

The scanned area is known for its huge systems of pit-falls for hunting wild reindeer. The area was probably most heavily used in the 15th century and the pit-fall system was in use until the end of the 17th century, when societal, economic and technological changes in the Sami population occurred. Today, there are no wild reindeers in Northern Norway, they are all domesticated.

Our investigation showed that some of the most common types of archaeological remains in Northern Norway could easily be detected on the DTM. For pit-falls the score was more than 90%. Some anomalies thought to originate from Sami settlements were marked on the model but when controlled in field only half of them proved to be actual settlements. This shows the importance of verifying the nature of anomalies in the landscape.

The project confirmed that in areas where archaeological finds are detected in the model, additional finds may be discovered during fieldwork. This held true both for new found house-sites dating from the time-period 1800 – 0 years BC, and several Sami meat caches, all found close to the pit-fall system. One of the settlements was found on the DTM, and when checked in the field additional similar settlement remains were uncovered nearby. The meat caches were rarely detectable on the DTM, but were easily found in the field. The reason why these are hard to detect on the DTM is because of their less regular and geometric shape, as they are pits built of large rocks and positioned in screes.

Another project aim was to investigate how well measurements in the model corresponded to measurements taken in the field. The model measurements had an average accuracy of 84% compared to field measurements. This accuracy is considered satisfactory for a typical archaeological use of such a huge and relatively coarse DTM.

This project showed that LiDAR can be of use also for detecting cultural remains typical to Northern Norway. Several types of structures or sites may not be found on a DTM, either because the point density is too low, because they are not visible above ground, or because the cultural heritage site is actually a natural structure given cultural meaning by the local population. The latter is often the case with Sami cultural heritage, such sites can hardly be distinguished from other natural structures only from investigating a DTM. But, as shown, some of the main Northern Norwegian cultural remains are visible in the model. In Norway there are vast areas where little is known about the existence of cultural monuments and remains. LiDAR can be a useful tool for covering blank spots in order to make priorities before time-consuming fieldwork is conducted, and provide accurate positioning of the sites visible on the DTM.

Part of the pit-fall system. Same area shown on air-photo and DTM. Photo by Statens kartverk, Geovekst.

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