https://orcid.org/0000-0002-0729-2953
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Abstract
Archival maps provide a valuable way to explore historical environmental data collected before the use of satellite imagery. Archival maps in their physical form cannot readily be used, however, beyond what the original cartographer intended. In this project, we describe a manual method to bring scanned archival maps into digital form using common tools in a geographic information systems (GIS) software platform. We rely on the important context of West Africa where a generation of geographers as part of the Terroir school worked with local agrarian communities to understand land use and land cover (LULC) dynamics. Specifically, we analyze archival maps of the Yatenga Province in Burkina Faso originally created by Jean-Yves Marchal, who used aerial photography from 1952 and 1973. This article describes the image processing steps to extract LULC data from scanned archival images using the graphical user interface of popular GIS tools. We compare our results to Marchal’s original maps and provide an alternative analysis of LULC change in the region using the newly extracted LULC data.
档案地图为研究卫星影像出现之前的历史环境数据提供了有价值的途径。然而, 除了制图员的意图之外, 我们无法立刻使用纸质档案地图。本文描述了一种手动方法：通过地理信息系统（GIS）的常用工具, 扫描档案地图并将其转换为数字形式。根据西非的重要背景（领地学派的地理学家与当地农业社区合作）, 我们旨在了解土地利用和土地覆盖（LULC）的变化。具体的, 我们分析了布基纳法索亚坦加省的档案地图。这些地图由Jean-Yves Marchal根据1952年和1973年的航空影像而制作。本文描述了通过流行GIS工具的图形界面从扫描档案图像中提取LULC数据的图像处理步骤。我们将结果与Marchal的原始地图进行了比较, 并利用提取的LULC数据为该地区的LULC变化进行了分析。
Los mapas de archivos son una forma valiosa de exploración de datos ambientales históricos recogidos antes del uso de las imágenes satelitales. No obstante, los mapas de archivos en su versión física no pueden usarse fácilmente más allá de lo que pretendía el cartógrafo original. En este proyecto, describimos un método manual para digitalizar mapas de archivos escaneados con las herramientas usuales en una plataforma de software de los sistemas de información geográfica (SIG). Nuestro trabajo se basa en el importante contexto del África Occidental, donde una generación de geógrafos, parte de la escuela Terroir, trabajó con las comunidades agrícolas locales buscando entender las dinámicas del uso del suelo y de la cobertura del suelo (LULC). Específicamente, analizamos los mapas de archivo de la Provincia de Yatenga, en Burkina Fasso, creados originalmente por Jean-Yves Marchal, quien usó fotografías aéreas de 1952 y 1973. Este artículo describe los pasos del procesamiento de imágenes para extraer los datos LULC de las imágenes de archivo escaneadas mediante el uso de la interfaz gráfica del usuario de herramientas populares de SIG. Comparamos nuestros resultados con los mapas originales de Marchal y ofrecemos un análisis alternativo del cambio de LULC en la región, utilizando los datos recién extraídos de LULC.
Acknowledgments
We are thankful to the anonymous reviewers who provided critical feedback to improve the quality and clarity of this article.
Notes
1 If there was more than one majority result from the Focal Statistics operation, the resulting value was “No Data.” We found that using the wedge shape helped fill in these scattered “No Data” pixels.
Additional information
Funding
Notes on contributors
Alfredo J. Rojas, Jr.
ALFREDO J. ROJAS, JR. is a Doctoral Candidate in Anthropology at the University of North Carolina, Chapel Hill, NC 27599. E-mail: [email protected]. He studies environmental change in West Africa, combining ethnographic fieldwork with geospatial data analysis.
Colin Thor West
COLIN THOR WEST is an Anthropologist with training in human ecology in the Department of Anthropology at the University of North Carolina, Chapel Hill, NC 27599. E-mail: [email protected]. He has conducted ethnographic fieldwork in northern Burkina Faso for twenty years. His work has documented patterns and processes of land degradation and rehabilitation using satellite imagery and participatory mapping.
Philip McDaniel
PHILIP McDANIEL is a GIS Librarian and the subject liaison for the Departments of Geography and City and Regional Planning at the University of North Carolina, Chapel Hill, NC 27599. E-mail: [email protected]. He provides research assistance and technical expertise for academic department and centers across the campus community.
Julia Longo
JULIA LONGO was a Graduate Student in the Department of Anthropology at the University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, at the time this research was conducted. E-mail: [email protected]. Her research interests include landscape archaeology, social zooarchaeology, and subsistence strategies of the past.
Vishnu Ramachandran
VISHNU RAMACHANDRAN is a product manager in the technology industry. He attended the University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, where he studied computer science and philosophy. E-mail: [email protected]. His research interests include image processing.
Natalie R. Gauger
NATALIE R. GAUGER graduated from the University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, in 2021 with a BA in Environmental Studies–Sustainability and a minor in Urban Planning. E-mail: [email protected]. As a Venture for America Fellow, she works at Trust Neighborhoods in Kansas City, MO 64106, doing affordable housing work.
Aaron Moody
AARON MOODY specializes in Biogeography, Remote Sensing and GIScience at the University of North Carolina, Chapel Hill, NC 27599. E-mail: [email protected]. His work primarily explores how ecological communities and biomes vary with physical and climatological gradients and their dynamics over time.