Bringing map collections to life in interactive web applications
ISBN 978-85-88783-11-9
Authors
1Buckley, A.; 2Allord, G.
1ESRI Email: abuckley@esri.com
2UNAFFILIATED Email: allordgreg@gmail.com
Abstract
Rich founts of information often sit untapped in unexplored library map drawers, inaccessible stores of map publishers, under-utilized archives in museums, and even unknown private collections. The maps in these collections could prove invaluable in providing views into the past, and these situations run counter to the common expectation that everything of value, or required for reference and research, best serves the needs of the mapping community by being available through the Internet. The web offers the best opportunity for making these collections available to wider audiences for a number of reasons. Online map collections can be explored without the geographic constraint of accessing a facility. Electronic formats are useful as a preservation copy, supporting viewing and reference or use for geographic analysis. User interfaces can allow the maps in the collections to be arranged in desired orders and compared to see change over time. Metadata about the maps can be presented in an organized and consistent manner allowing for better search and selection strategies. The process of building a map collection for dissemination online, and then the task of creating a web interface to view the collection often seem a daunting task for map collection custodians. Transitioning paper maps to electronic form, as well as web application development, are often outside of their scope of experience and knowledge. While it is recognized some libraries and organizations can successfully transition a limited number of maps, transitioning a great number of maps from paper for use in a GIS can be great investment in time and resources. As a result, these valuable collections continue to remain unnoticed and unused. Drawing on the successful implementation of the USGS Historical Topographic Map Explorer, we present a set of resources that have been developed to allow others to create and share map collections online. The USGS Historical Topographic Map Explorer is a web application that provides access to over 178,000 maps dating from 1884 to 2006. The app organizes the maps by spatial extent, time, and map scale. It provides users with a timeline from which they can easily select the maps they want to explore and it arranges them in a table of contents that can be reorganized by the users. It also allows the maps to be downloaded to a user's desktop. The simplicity of the application forces users to focus on the main objective that it supports: selection and comparison of the maps of interest. In this presentation, we demonstrate a solution for converting map collections to a format that can be shared online. We describe the processes for scanning, georeferencing, and building metadata for the maps. We explain how advance effort spent gathering metadata can greatly facilitate the workflow to convert scanned images to spatially referenced maps down the line. We also explore technical challenges, including the format and age of source maps, physical condition of the maps, visual characteristics of color and detail of small text, and occasional close spacing of geographic features such as contour lines. Then we explain how the map images are organized into services accessible from the web. This is done using a tool designed for scanned map collections that automates the creation of a mosaic dataset that references image services. Using image services addresses issues of high-resolution of geographic data versus large file size; providing derivate copies of original scanned, georeferenced images; and the viewing on a computer screen of large-scale maps that have variations in dates, details and map scales. Finally, we demonstrate a template that can be used to produce the user interface in an explorer app. Our primary goal is to share the tried and tested workflows used to create the Historical USGS Topographical Map Explorer as a set of useful, well-documented, and repeatable methods that others can use to share their own map collections.
Keywords
map collection; web map; historical map