GastFarm2016_Report

Project Name: Gast Farm<br> Project Location: Iowa, United States<br> Project Date: 2016 Gast Farm is a 13-hectare archaeological site located in the Mississippi River valley in southeast Iowa. Gast Farm is one of the largest and best-preserved Woodland sites in the region, with both Middle Woodland (Havana Hopewell, ca. 50 B.C.–A.D. 250) and initial Late Woodland (Weaver, ca. A.D. 350–500) deposits. Additionally, a large mound was once present, and remnants of geometric earthworks also suspected. The PIs research seeks to is to understand the interanal structure and layout of the Woodland communities at Gast Farm, which can contribute to knowledge of Middle and Late Woodland domestic and corporate-ceremonial spheres, i.e., residential as well as sustainable and symbolic communities. PI William Green collaborated with SPARC researcher Adam Barnes to produce orthorectified images and a digital elevation model (DEM) of the Gast Farm site from aerial imagery collected in 1990, using AgiSoft Photoscan. The orthophotos reveal distinct soil discolorations because the original photos were taken after the field had been disked, planted, and rained on, and only a few days after row crops (corn) had emerged. Soil discolorations indicate large-scale cultural features such as middens (dark colors) and a mound and possible geometric earthworks (light colors). The orthophotos also show a series of narrow linear discolorations exactly 10 m apart that represent the paths created during the controlled surface collection that was underway at the time the photos were taken. The DEM produced by orthophoto rectification has a 50-cm resolution, which is unfortunately is not sufficiently sensitive to detect possible mound or earthwork features after they have been leveled and plowed. This work is part of a larger 2016-2018 project at Gast Farm, which combined GIS development, aerial imagery analysis, and geophysical survey. Defining community organization, locating any subsurface traces of the mound, and determining the reality of the suspected earthwork constituted key research objectives. Over the course of the project, the Gast Farm team (1) identified the Middle Woodland (Havana-Hopewell) community plan, (2) determined no geometric earthworks were present but discovered six additional mounds, and (3) confirmed and expanded the Late Woodland (Weaver) community plan. In the process of obtaining these results, the project also accomplished several methodological advances: it (1) demonstrated the viability of magnetic gradiometry for identifying Woodland residential and mortuary features in Mississippi Valley alluvial fans, (2) showed how to incorporate legacy oblique aerial photography in a georeferenced GIS, (3) indicated the promise of drone-based photogrammetry in identifying cultural features beneath crop cover, and (4) modeled the virtual reconstruction of leveled mounds. Fieldwork and analyses were conducted in 2016-2018 through a grant from a National Geographic Society Committee for Research and Exploration (project 9938-16). This research was also supported by a SPARC Data &amp; Analytics Award. The SPARC Program is based at CAST at the University of Arkansas, and is funded by a generous grant from the National Science Foundation (BCS #1519660). Additional support for project archiving was funded by the SPARC Program in 2020 (BCS #1822110). A Beloit College Keefer Senior Faculty Grant and a developmental leave from Beloit College supplemented the NGS and SPARC support. Research was also aided by effort provided by Beloit College students and individuals at several partner institutions, notably the Midwest Archeological Center of the National Park Service (Lincoln, NE; MWAC), the Office of the State Archaeologist of the University of Iowa (OSA), and Arizona State University. The DigitalGlobe Foundation also provided access to satellite imagery (not included in this archive).项目名称：盖斯特农场（Gast Farm） 项目地点：美国爱荷华州 项目时间：2016年 盖斯特农场是一处占地13公顷的考古遗址，坐落于爱荷华州东南部的密西西比河谷地带。该遗址是该区域规模最大、保存最完好的伍德兰文化期（Woodland Period）考古遗址之一，埋藏有中伍德兰文化期（哈瓦那霍普韦尔文化，约公元前50年—公元250年）与初始晚伍德兰文化期（韦弗文化，约公元350年—500年）两类遗存。此外，遗址曾存在一座大型土墩，同时疑似留有几何形土筑工程遗迹。 本项目的研究目标为解析盖斯特农场遗址伍德兰文化期聚落的内部结构与布局，相关成果可丰富学界对中、晚伍德兰文化期家庭与社群礼仪圈层——即居住型、可持续性与符号化社群——的认知。项目负责人威廉·格林（William Green）联合SPARC研究员亚当·巴恩斯（Adam Barnes），基于1990年采集的航空影像，使用Agisoft Photoscan生成了盖斯特农场遗址的正射校正影像（orthorectified images）与数字高程模型（Digital Elevation Model, DEM）。 由于影像拍摄时，农田已被犁耕、播种并经历降雨，且仅在大田作物（玉米）出苗数日后完成拍摄，正射校正影像呈现出清晰的土壤色泽差异：深色色泽代表粪土堆（midden）这类大型文化遗存，浅色色泽则对应土墩与疑似几何形土筑工程遗迹。此外，影像中还可见一系列间距恰好为10米的狭窄线性色泽带，它们对应本次影像拍摄时正在开展的控制性地表采集工作所留下的作业路径。 本次生成的数字高程模型分辨率为50厘米，但遗憾的是，其敏感度不足以探测经过平整与犁耕后的土墩或土筑工程遗迹。 本项研究是盖斯特农场2016—2018年大型项目的组成部分，该项目整合了地理信息系统（Geographic Information System, GIS）开发、航空影像分析与地球物理勘探工作。明确聚落组织形态、定位土墩的地下遗存、证实疑似土筑工程的真实性，是本次项目的核心研究目标。 在项目推进过程中，研究团队取得了多项方法学进展：其一，证实了磁梯度测量法（magnetic gradiometry）在密西西比河谷冲积扇区域识别伍德兰文化期居住与丧葬遗存的可行性；其二，探索了如何将遗留的倾斜航空影像纳入地理参考型地理信息系统；其三，验证了无人机摄影测量技术（drone-based photogrammetry）在识别作物覆盖下文化遗存的应用前景；其四，构建了平整后土墩的虚拟重建（virtual reconstruction）模型。 2016—2018年的野外工作与数据分析依托美国国家地理学会研究与探索委员会提供的资助项目（项目编号：9938-16）完成。本研究同时获得了SPARC数据与分析奖的支持。SPARC项目设于阿肯色大学CAST中心，其资助方为美国国家科学基金会（BCS #1519660）的专项拨款。2020年，SPARC项目为项目档案留存提供了额外资助（BCS #1822110）。贝洛特学院基弗高级教师基金与贝洛特学院的发展休假资助补充了美国国家地理学会与SPARC项目的资金支持。 本研究同时得到了贝洛特学院学生与多所合作机构人员的协助，包括美国国家公园管理局中西部考古中心（内布拉斯加州林肯市，MWAC）、爱荷华大学州立考古学家办公室（OSA）以及亚利桑那州立大学。DigitalGlobe基金会提供了卫星影像访问权限（本档案未包含该部分影像）。