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Reconstructing the Past through Utah Sanborn Fire Insurance Maps: Home

An innovative portal for all available Utah Sanborn Fire Insurance Maps hosted at the J. Willard Marriott Library.

About This Project (Video Presentation)

About Sanborn Fire Insurance Maps

The Sanborn Map® Collection contains large-scale, detailed maps from 1867 -1969 depicting the commercial, industrial, and residential sections of cities. They were designed in 1866 by surveyor D.A. Sanborn to assist fire insurance agents in determining the risk associated with insuring a particular property. The D.A. Sanborn Co. was the first to offer insurance maps on a national scale in response to the growth of urban communities after 1850. The company's surveyors meticulously documented the structural evidence of urbanization - building by building, block by block, and community by community.

Sanborn Maps® illustrate the size, shape, and construction material of dwellings, commercial buildings, and factories. Details include fire walls, windows and doors, style and composition of roofs, wall thickness, cracks in exterior walls, and elevators. They also indicate building use, sidewalk and street widths, layout and names, property boundaries, distance between buildings, house and block numbers, location of water mains, hydrants, piping, wells, cisterns, and fuel storage tanks. The maps are color-keyed. Please see map key to the left for details. For many years the maps were handmade and hand-colored. After 1911, corrections and amendments were pasted on top every few years.

The Marriott Library has digitized and georeferenced maps for Utah cities ranging from 1884 to 1950.

The Georeferencing Process

Georeferencing is a process by which a 2-dimensional print map or photograph's existence is defined within physical space.  The process is achieved by giving the image a latitude and longitude that is dependant upon a particular map projection system.

Original scanned tiffs (approximately 148mb per map) were converted to smaller web sized images (2-3mb) using Photoshop to allow for easy access while preserving image quality.  Each map was georeferenced using ArcGIS 10, aligning each image to its appropriate geospatial location according to reference layers consisting of satellite imagery, street centerlines and parcel data.  The georeferenced maps were then converted to KMZ files using Global Mapper software, allowing each map to be viewable in Google Earth. 

While care has been taken to maintain georeferencing accuracy, some map features have changed over time, resulting in each map being georeferenced as closely to its appropriate location as possible.  In addition, some maps were unable to be georeferenced due to lack of reference points.  These tend to occur on maps with multiple locations pieced together on a single page (see full catalog for more information).

KMZ files contain a georeferenced sheet overlay from the Sanborn Fire Insurance Maps for a specific city/year.  When downloaded and opened, the .kmz file is accessible for viewing in Google Earth and other GIS software systems.  Multiple .kmz files can be loaded into a GIS software system in order to view a continuous set of sheet overlays.

Zip files contain a .jpw, .jpg, .jpg.auz.xml and .jpg.ovr representing a single georeferenced sheet overlay from the Sanborn Fire Insurance maps for a specific city/year.  When downloaded and opened, the zip files are accessible for viewing in ArcGIS and other GIS software systems.  Multiple zip files can be loaded into a GIS software system in order to view a continuous set of sheet overlays.

Subject Specialist

Justin Sorensen's picture
Justin Sorensen
Contact:
GIS Specialist

Creativity & Innovation Services
GIS Services
801-585-7349
Website / Blog Page

Staff Acknowledgements

GIS Services Staff

Justin Sorensen - GIS Specialist
Caitlyn Tubbs - Data & Visualization Intern (Former)

USpace Staff

Donald Williams - IR Coordinator (Former)
Cindy Russell - IR Workflow Specialist

Article Publication

Read about our project in the March / April 2015 edition of D-Lib Magazine.

http://www.dlib.org/dlib/march15/sorensen/03sorensen.html

Understanding the Maps

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