Hillforts are fortified archaeological sites built from the Neolithic to Early Middle Ages within the area of Europe. They were usually surrounded by fortifications consisting of various combinations of ramparts and ditches, which today constitute their most striking remains. Although magnetometry surveys are commonly used for spatial identification of ramparts and ditches, a different method must be employed for directly obtaining depth information. Hence, we evaluate the potential of electrical resistivity tomography (ERT) for surveying hillfort fortifications. Within three hillforts of different ages in the Czech Republic, we investigated various features affecting the imaging ability of ERT, including bedrock type, building material, present-day condition of fortification, impact of past or recent agricultural activities, and field settings of the ERT method. Supported by additional information from magnetometry and electromagnetic surveys, the results show that ERT is most applicable in cases of stony ramparts, ditches carved into rocky bedrock or well-preserved earthen ramparts. Poorer results were achieved upon active and/or recently active agricultural lands, where fortifications have been gradually destroyed by ploughing. The remains of stony ramparts remained distinguishable in the latter case, but mere traces of earthen ramparts and ditches were invisible to ERT due to mixing of fortification material with on-site soil. ERT is a unique method for detailed investigation of both ramparts and ditches by which a structure and its extent can be evaluated to indicate the function of a settlement and obtain information about former environmental conditions, population, land use and/or human–environmental interaction.

中文翻译：

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电阻率层析成像在山丘防御工事测绘中的能力和局限性

Hillforts 是欧洲地区从新石器时代到中世纪早期建造的坚固考古遗址。它们通常被防御工事所包围，防御工事由各种城墙和沟渠组合而成，今天构成了它们最引人注目的遗迹。虽然磁力测量通常用于对城墙和沟渠的空间识别，但必须采用不同的方法来直接获取深度信息。因此，我们评估了电阻率断层扫描 (ERT) 用于测量山堡防御工事的潜力。在捷克共和国的三个不同年龄的山丘中，我们调查了影响 ERT 成像能力的各种特征，包括基岩类型、建筑材料、当前的防御工事状况、过去或近期农业活动的影响、和 ERT 方法的字段设置。在来自磁力测量和电磁测量的额外信息的支持下，结果表明 ERT 最适用于石质城墙、刻在岩石基岩中的沟渠或保存完好的土质城墙。在活跃和/或最近活跃的农业土地上取得了较差的结果，其中防御工事已被耕作逐渐摧毁。在后一种情况下，石质城墙的遗迹仍然可以区分，但由于防御工事材料与现场土壤的混合，ERT 看不到仅有的土质城墙和沟渠的痕迹。ERT 是一种独特的方法，用于详细调查城墙和沟渠，通过该方法可以评估结构及其范围，以指示定居点的功能并获得有关以前环境条件的信息，