The ArcGIS Online US Geological Survey (USGS) topographic map collection now contains over 177,000 historical quadrangle maps dating from 1882 to 2006. The USGS Historical Topographic Map Explorer app brings these maps to life through an interface that guides users through the steps for exploring the map collection:Find a location of interest.View the maps.Compare the maps.Download and share the maps or open them in ArcGIS Desktop (ArcGIS Pro or ArcMap) where places will appear in their correct geographic location. Save the maps in an ArcGIS Online web map.
Finding the maps of interest is simple. Users can see a footprint of the map in the map view before they decide to add it to the display, and thumbnails of the maps are shown in pop-ups on the timeline. The timeline also helps users find maps because they can zoom and pan, and maps at select scales can be turned on or off by using the legend boxes to the left of the timeline. Once maps have been added to the display, users can reorder them by dragging them. Users can also download maps as zipped GeoTIFF images. Users can also share the current state of the app through a hyperlink or social media. This ArcWatch article guides you through each of these steps: https://www.esri.com/esri-news/arcwatch/1014/envisioning-the-past.Once signed in, users can create a web map with the current map view and any maps they have selected. The web map will open in ArcGIS Online. The title of the web map will be the same as the top map on the side panel of the app. All historical maps that were selected in the app will appear in the Contents section of the web map with the earliest at the top and the latest at the bottom. Turning the historical maps on and off or setting the transparency on the layers allows users to compare the historical maps over time. Also, the web map can be opened in ArcGIS Desktop (ArcGIS Pro or ArcMap) and used for exploration or data capture.Users can find out more about the USGS topograhic map collection and the app by clicking on the information button at the upper right. This opens a pop-up with information about the maps and app. The pop-up includes a useful link to a USGS web page that provides access to documents with keys explaining the symbols on historic and current USGS topographic maps. The pop-up also has a link to send Esri questions or comments about the map collection or the app.We have shared the updated app on GitHub, so users can download it and configure it to work with their own map collections.