Georectified Mosaic of Aerial Images of Baltimore City in 1927

Landscape analyses are typically done using spatially explicit color aerial imagery. However, working with non-spatial black and white historical aerial photographs presents several challenges that require a combination of techniques and approaches. We analyzed 93 aerial images covering 544 km2 (210 mi2) including all of Baltimore City, and an area immediately adjacent to the city known at the time as the Metropolitan District of Baltimore County. The images were taken from a biplane between October 1926 and February 1927. High-resolution scans were georeferenced and georectified against modern satellite imagery of the area and then combined to create a single raster mosaic. This process converted the images from a disparate set of photographs into a spatially explicit GIS data set that can be used to observe changes in land patches over time—and ultimately integrated with other long-term social, economic, and ecological data.

景观分析通常采用空间显式（spatially explicit）彩色航空影像开展。然而，处理非空间黑白历史航空影像存在诸多挑战，需结合多种技术与方法方可解决。本研究共分析93幅航空影像，覆盖面积达544平方千米（210平方英里），涵盖完整的巴尔的摩市，以及彼时被称为巴尔的摩县大都会区的城市邻近区域。这批影像于1926年10月至1927年2月期间由双翼飞机拍摄获取。研究团队以该区域的现代卫星影像为基准，对高分辨率扫描影像完成地理参考（georeferenced）与几何校正（georectified），随后将其拼接为单幅栅格镶嵌图（raster mosaic）。该流程将原本分散的影像集转化为空间显式地理信息系统（GIS）数据集，可用于观测随时间推移的土地地块变化，并最终可与其他长期社会、经济及生态数据进行整合。