The Sanborn Overlays – Instructions and Tips

Each set of Sanborn overlay pages has two possible views: an embedded view that is contained on the page itself, and a linked view that will take you to a larger map hosted by ESRI, a Geographical Information System provider. 

*To zoom and out, use the +/- buttons or your scroll wheel, if you have one
*Each map consists of several layers, including the underlying current aerial or map, one or more mosaic elements (see additional note below regarding mosaic elements), and buildings or other elements included in our website’s Where Are We?  feature (see below). Clicking on the layer icon ()will allow you to toggle various layers on or off.
*Opacity of the various layers can be changed by selecting the layer, clicking on the right arrow > where you can select opacity of the selected layer. 
*Link here for legends and keys that Sanborn typically used in the colored maps; link here for legends and keys for the black and white maps. These changed somewhat over time so may not be universally applicable. 
*Colored dots link to information about buildings or other historical features included in the Where Are We? feature of our website. The dots are color-coded (click on legend icon ) to indicate the time frame in which the feature was added.  Toggle the Historical Features layer to turn this on and off. Clicking on the dots will take you to a link for the applicable Where Are We? page. 
*You can use the measure button to draw a line or enclosed area and measure length or area. Clicking on it again will make the line disappear.
*The basemap button ()allows you to select what you want to see under the Sanborn overlay — e.g., an aerial view, a street map, etc.

Note re mosaic elements: Each Sanborn map series consisted of two or more sheets, with an index, or overview, page that provided an overview of the area covered by each series. The overview also shows the sheet number for each area covered. Our Sanborn overlay maps were created by layering several individual sheets or groups of sheets (mosaic tiles) over a single contemporary aerial view or map. Occasionally, the mosaic elements slightly overlap and may obscure some information. Each layer can be toggled on and off with the layer button, so where there are overlapping mosaic tiles, you may wish to view each layer separately. We recommend that you begin your viewing with the overview layer, then toggle the separate mosaics and/or Historic Features layer on and off, and set their opacity as desired. 

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