Less than a decade after the country’s founding, the US federal government began to pay systematic attention to mapping the immense land-area that was to become the United States. While several military and civilian surveying efforts resulted, there were conflicts and a lack of standardization.
A mere 94 years after the original Land Ordinance of 1785 directed the surveying and classification of public lands, in 1879 the US Geological Survey (USGS) was established for that purpose.
135 years after the USGS began its mission, the technology of geospatial PDF as utilized by North Avenue Technologies‘ Memento Server makes it possible to see history represented through a mosaic of 92,000 maps from USGS historical archives, including the ability to zoom in for the tiniest details.
The results are breathtaking (see the videos at the end of this post).
Converting archival scans to geospatial PDF
The USGS scanned their maps to geospatial PDF for three reasons:
- the ubiquitous nature of PDF
- the image-compression possible in PDF. Many of the original scans – uncompressed and 1200 dpi – are over 1 GB, impractical for serving on the web
- the geospatial encoding possible in PDF
Although users can download historical USGS maps for free, North Avenue’s Memento Server takes the experience to another level, stiching together map edges to form a seamless whole, and providing immediate comparison with other time-periods.
As part of work they performed for the US Army Geospatial Center, North Avenue developed a means of creating a mosaic of geospatial PDFs. To showcase their Memento Server technology they obtained a copy of all the historical maps from the USGS’s geospatial PDFs holdings.
Patrick Graves, North Avenue’s CEO and founder told me: “When I first got the maps, I immediately loaded them on my laptop running our Memento Server software. I was pretty excited to see how cool the old maps looked when stitched together.”
North Avenue’s USGS Historical Maps implementation is a custom implementation of Open Layers. It accesses the Memento Server to retrieve map tiles and link to the underlying PDF files.
Features of the current Memento server implementation
- View maps from up to 6 time-periods
- Blend views of current road maps with historical USGS surveys
- Zoom out to view the entire country; zoom in to view the smallest details
- Locate towns and cities by name
- Open any of original maps in view as downloadable PDF files
Check out the Memento server’s mosaic of 92,000 USGS maps! Here’s a preview…
The scope of USGS surveys over time
This application presents over 92,000 USGS maps at once. By clicking on the year ranges (at the top right) we can show the coverage of the US over time.
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Los Angeles in the 1880s, and today
By working the slider in the bottom-left corner we can “fade out” the 1880s map of Los Angeles to reveal the present-day.
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