1975 UMRS Land Cover/Land Use -- Open River 1

The Great River Environmental Action Team (GREAT) was a federal/state multi-agency cooperative program established in the late 1970's to evaluate current resource management practices and develop management strategies for the Upper Mississippi River (UMR). One of the problems facing the GREAT project was the lack of available information on many of the river's components. One project implemented by GREAT was the creation of a land cover/land use (LCU) database derived from color infrared aerial photography collected in 1975. Mississippi River Pools 3 through 10 were photographed at a scale of 1:9,600, and Lock and Dam 10 to the Ohio River were photographed at a scale of 1:24,000. The program's photo interpreters delineated whatever features could be viewed on the photos, using a minimum mapping unit that was less than half an acre. A contractor was hired to transfer the photo overlays for Pools 3 through 14 onto 1:24,000-scale USGS quadrangles, then automate the data using the geographic information system (GIS) program PIOS. The data were also distributed as map books that contained 1:6,000-scale enlargements of the photos and their overlays. During the data transfer process; the contractor hired to automate the data generalized it to a 2.5 acre minimum mapping unit. Documentation archived by the GREAT project described this automation process as; some polygons smaller than 2.5 acres and linear features were incorporated into nearby polygons. Others were manually enlarged so that the data contained within would be preserved. All generalizations were made in accordance with the guidelines established for the GREAT projects. The digital data sets were then enhanced by the GREAT project. Unfortunately no record of the enhancements or an archive of the original digital dataset are known to exist. The enhanced digital data, copies of the aerial photo overlays, copies of most of the map books, and some of the photos themselves were archived and preserved by the various agencies that participated in the GREAT project. These data were then passed to the Upper Midwest Environmental Sciences Center (UMESC) in the late 1980's and 1990's when the center became the administrator for the Upper Mississippi River System's Long Term Resource Monitoring Program (LTRMP). Comparisons of the archived digital data set to the photos and their overlays displayed discrepancies that were difficult to document. The 1975 data set is viewed by many as an important baseline data set, so in 1999 UMESC decided to use the archived photo overlays to (1) address the data discrepancies by reautomating Pools 3 through 14, and (2) complete the data set by automating Lock and Dam 14 to the Ohio River.大河环境行动小组（Great River Environmental Action Team, GREAT）是一项于20世纪70年代末设立的联邦-州级多机构合作项目，旨在评估密西西比河上游（Upper Mississippi River, UMR）现行的资源管理实践，并制定相应的管理策略。该项目面临的核心难题之一，是该河流诸多组成部分的可用信息匮乏。由GREAT牵头实施的一项工作为：基于1975年采集的彩色红外航空摄影资料，构建土地覆盖/土地利用（land cover/land use, LCU）数据库。密西西比河3号至10号河段的摄影比例尺为1:9600，10号船闸大坝至俄亥俄河河段的摄影比例尺为1:24000。该项目的影像解译人员对影像上可识别的地物进行勾绘，采用的最小制图单元小于0.5英亩。项目方聘请承包商将3号至14号河段的影像叠加图层转换至1:24000比例尺的美国地质调查局（USGS）地形图幅上，随后借助地理信息系统（geographic information system, GIS）软件PIOS实现数据自动化处理。该数据还以地图册形式发布，其中包含1:6000比例尺的影像及其叠加图层的放大图。在数据转换过程中，负责自动化处理的承包商将数据的最小制图单元统一调整为2.5英亩，并进行了概括化处理：将小于2.5英亩的部分多边形与线性地物并入邻近多边形，对部分地物进行手动放大以保留其包含的属性信息。所有概括化处理均严格遵循GREAT项目制定的规范。随后GREAT项目对该数字数据集进行了增强处理，但目前未发现相关增强操作的记录，也无原始数字数据集的存档留存。经增强处理的数字数据、航空影像叠加图层副本、多数地图册副本以及部分原始影像，由参与GREAT项目的各机构进行了归档保存。20世纪80年代末至90年代，当中西部环境科学中心（Upper Midwest Environmental Sciences Center, UMESC）成为密西西比河上游系统长期资源监测计划（Long Term Resource Monitoring Program, LTRMP）的管理方后，上述数据被移交至该中心。经比对，归档的数字数据集与原始影像及其叠加图层存在难以溯源的差异。由于1975年数据集被众多研究者视为重要的基准数据集，UMESC于1999年决定依托归档的影像叠加图层开展两项工作：一是重新对3号至14号河段进行自动化处理，以修正数据差异；二是对14号船闸大坝至俄亥俄河河段开展自动化处理，以完善该数据集。