2013-04-08: Accessing Historic Imagery

For many years we made our hardcopy archive of historic aerial imagery available by scheduling appointments with our office. Only during office hours were the documents available to those who needed them. Over time these hardcopy images become worn out through use.

After recognizing a demand for these imagery products and desiring to improve services through increased access we began (~2009) offering imagery through a GIS Online website. We used a scanner to digitize and then georeferenced each image within the 1970 and 1980 sets. Today, those in need of this imagery archive consisting of more than 40 years can access it through our website as they need it.

Please review the instructions below to learn how to access the individual tiles of 1970 and 1980 imagery. Other years (1990s, 2000s) are less cumbersome to access as they are seamless mosaicked images available in the “Map Layers” (table of contents for the map or layers listing).

· From the York County or GIS home page (http://www.yorkcountygov.com/GIS). Navigate to GIS Online Mapping Applications.

· Click on the ‘Historic Imagery Viewer’ link button.

· Once the maps appears navigate to the area of interest

· The 1970 and 1980 imagery is arranged in a mosaic of tiles. Each tile is indexed and on a separate map layer. All imagery layers are turned off (not visible) by default. Use the Image year and index label (see above image) to determine the correct layer to turn on (make visible). In this example the image of interest is the 1970 image grid index (layer) I-6. Click on the ‘I want to…’ button (in the upper-left corner of the map) and then select the ‘Turn map data on/off’ item.

· A map layers panel should open on the left side of the browser. This is a ‘table of contents’ of all the map layers in this map application. The visibility of each layer and layer group is controlled through this table of contents. Click on the ‘+’ next to the layer group that contains the 1970, ‘I’ layers to expand it. Click on the check box next to the ‘I-6’ layer (may need to scroll) to make it visible.

· The image should now appear. If the image does not appear it may be necessary to zoom in. Click on the zoom slider control to the left of the ‘I want to..’ button (this slider is very transparent until the mouse hovers over it). Click on the ‘+’ (at the top of the slider control) to zoom in. Click once and then see if the image appears. If not, continue to click until the image appears.

· To turn the grid index layers off uncheck these layers in the table of contents.

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