University Map Library Historical Air Photo Digitization Project

By Eva Dodsworth Geospatial Data Services Librarian University of Waterloo

Abstract

In October 2007, the University Map Library launched an archival air photo scanning and digitization project, where approximately 1500 historical air photos for the years 1930 and 1945­ 47 of Kitchener­Waterloo and surrounding areas were scanned, digitized, georeferenced and provided on the internet for viewing and downloading. A number of image formats have been made available to the users, including both higher and lower resolution outputs as well as GeoTiffs for GIS purposes and Google Earth’s KMZ files for the utilization of the georeferenced images in Google Earth or Google Maps.

The Map Library’s Digital Historical Air Photo Project website was created for all users – the public and academic communities alike. This project has addressed several issues that have been associated with the usage of archival air photos by library clients. It has also exposed the Region of Waterloo’s history to many members of the community who have not been exposed to the library’s paper air photo collection.

Objectives

Preservation and Archival of Photos

The Map Library’s aerial photography collection is highly used by both academic scholars and the public community. One of the most important objectives for the library was to decrease the amount of handling the original photographs were being exposed to. Images were often handled, scanned by the users and then filed in the cabinets by library staff. Occasionally photographs were placed inadvertently in wrong cabinets by the users, and a great deal of effort was spent locating them again. Digitizing the historical photos will significantly decrease the photos’ physical usage, as well as eliminate redundant scanning of them.

Offer Easy Online Access to Photos

With library users limited to the map library’s business hours, offering pre­scanned imagery 24/7 on the internet will increase the usage of the photos, will offer convenience, and will expose the photos to many people who otherwise may not have known about them.

Offer Georeferenced Photos for Easier Navigation, Interpretation and Map Making

Each photo is available in GeoTiff format which retains the geographical coordinates of the photo. Using a desktop GIS program, such as ArcGIS, users can display the photo geographically­accurately on the earth’s surface. Other GIS files can be overlaid such as streets and points of interest to assist in the navigation of these older photos.

A street file, for example, may provide the user with streets lines and corresponding street names so that location and landscape objects in the photos can be better identified. Many areas of the Region look very different today than they did 80 years ago. Most rural areas are unrecognizable and many users of paper air photos have been known to spend hours determining the exact location of the photo.

The georeferenced images can be used in ArcGIS to create maps and analyze information. With the ability to overlay other features, users can more accurately examine land use changes over time.

Offer Georeferenced KMZ files for non­GIS users

With the invaluable benefit of having spatial information associated with the photographs, KMZ files were created for Google Earth users who do not have access to ­or the interest in­ GIS programs. Using a third party resource, such as Google’s online mapping program, anybody can view the images, can place them accurately on the earth’s surface and can use Google’s street files and points of interest to navigate around the photos. The KMZ files are simply zipped image files and are very easy to work with. They are about 1/5 th the size of the original GeoTiff and open in Google Earth as easily as other image formats.

Offer an online index to the photo collection

Due to the changing landscape over the last 80 years, using flight­line indexes has proven to be very time consuming and ineffective. Many library users struggle to find the correct photo they are interested in, and several collections are represented on one flight indexes, adding more to the confusion. Map Library staff created a clickable index on the web that uses current streets and municipal boundaries as navigational aides in finding the user’s photo of interest. Clicking on the area of interest on the index leads the user to the actual photo.

Methodology

Scanning Historical Air Photos

The archival scanning project consisted of scanning historical air photos for the years 1930 and 1945­47.

Air Photos Published by the National Air Photo Library;

Copyright Free

Year Scale # of Photos

1930 1:18,500 667

1945 1:20,600 136

1946 1:15,500 214

1947 1:11,700 – 1:12,300

171

The photos were burned to a DVD for archival purposes, and copies of the photos were used for the online project.

Digitizing Photos for the Web

The original scanned images were cropped to eliminate the outer edges of the photographs. Cropping was completed in Jasc’s Paint Shop Pro graphic program. Casual, part­time staff were trained to georeference using ArcGIS’ ArcMap 9.2 program.

Using paper indexes, the staff found the geographical location of the air photos and began georeferencing the urban areas of Kitchener­Waterloo and Cambridge starting with the 1930s. Once the urban areas for the years 1945­47 were completed, staff began working on the rural areas.

Once the images were georeferenced, they were inspected for alignment and tonal quality. Due to a large overlap in photos, only the higher quality images were used to create the final images.

The images were cropped into even tiles using a 2.5 x 2.5 km grid. Approximately 2­3 photos made up a tile. ArcMap was used to export the view of the image in Tiff format with the accompanying World file (a text file with spatial coordinates). The view did not export exactly to the boundaries of the grid, so ForestryGIS, a free GIS program, was used to make the final clip of the image, producing both a Tiff and a lower resolution Jpg image file.

The scanner used for this project was a 12x17 Microtek MRS 3200A3 model scanner. Casual, part­time library staff who work at the library service desk were trained on the scanning procedures and scanned the air photos during their scheduled desk shifts.

Image properties

• Tiff

• 600 DPI

• 8‐Bit grey scale

• ~30 Megs

• Time : 3 minutes to scan and save

An overlap of photos

The KMZ file was created in Google Earth. The image was added into Google Earth as an image overlay and coordinates were adjusted to correctly align the image to the earth’s surface.

1930 image overlay on Google Earth’s current imagery

Each image was clipped to the boundary of the grid file

ForestryGIS was used to crop the final image to the tile boundary.

Methodology Steps at a glance

Step Description Software Used Specifics

1 Crop Images Jasc Paint Shop Pro Removal of photo edges

2 Georeference Images

ArcMap 9.2

3 Create Image Tiles ArcMap 9.2 Exported as Tiff, with world files, 8‐ bit colour, 300 dpi ; ~ 7 megs.

4 Finalize Image Tiles for the Web (crop to tile boundary)

ForestryGIS ‐ Create Tiff (5 megs)

‐ Create World File (1 KB)

‐ Create Jpg (100 KB)

5 Create PDF ArcMap 9.2 200 dpi ; ~1.5 Megs

6 Create KMZ Files Google Earth Add image as overlay and adjust coordinates. Save as KMZ; ~1.5 Megs

7 Create Webpage Contribute, Fireworks, Dreamweaver

Design new webpage for project; create clickable indexes; upload all image files to the web

Offering images for Download

A website was created to provide the public with access to all of the image formats described above. Users can find their images by navigating to their geographical area of interest by clicking on a graphical index. Every tile has its own page and offers images from all the years that are available for the geographical area bounded by the tile.

An example of the information available from the webpage for tile number IM31

This website is available at : http://www.lib.uwaterloo.ca/locations/umd/project

Results and Conclusion

Aerial photography captures moments in time, offering a pictorial preservation of history. This project offers convenient access to Kitchener­Waterloo’s local history, and offers users the added value of combining the photos with GIS technology.

Georeferenced aerial photography accurately places the photograph on the earth’s surface, making the information richer, revealing hidden patterns and displaying informative results. When using mapping programs such as Google Earth, one can find their home today and with a simple click, view the historical image to see how the land was used 70 years ago. Combining the old and the new places coffee shops in the middle of farmer’s fields; places highways on top of old stone school houses. GIS technology expands the usage capabilities of aerial photography and attracts interest to the library’s collection and the Region’s local history.

Using ArcMap – combining the old and new – a historical photograph overlaid with semi‐transparent features from 2008 (buildings, streets creeks, and forests)

Vector data courtesy of the City of Waterloo

A display in Google Earth: with one click, the user can go back in time.

Acknowledgements

Map Library staff have spent hundreds of hours on this project ‐ both casual, part‐time and full time staff contributed in the scanning, cropping, georeferencing and tiling of a very large collection. Thank you to everybody for their dedication, attention to detail and for the many hours spent often working on repetitive tasks.