Digital versions of ILHAP photographic paper prints are available by county as MrSID compressed <filename>.sid files, which can be saved to your computer's hard drive. Alternatively, the .sid files may be viewed either with your Web browser, after the installation of a plug-in.
Instructions for downloading Illinois Historical Aerial Photography in MrSID format, a screen shot of the Interactive Mapping Web Interface, and descriptions of the navigational tools of the Interactive Mapping Web Interface are detailed below.
|Overview Map||Turn the Overview Map displayed in the upper left corner of the map frame on or off.|
|Zoom In||Enlarge the map image by clicking on a spot or dragging a rectangle around the area of interest.|
|Zoom Out||Reduce the map image by clicking on a spot or dragging a rectangle around the area of interest.|
|View One Photo||Graphically select a single photograph for viewing. A separate file-viewing window appears to display the photograph if you have downloaded the appropriate MrSID plug-in or viewer.
There is no need to specify an "active" layer.
|Select Multiple Records||Graphically select multiple records by dragging a rectangle around the area of interest. Features in the rectangle will be selected and highlighted in light blue. A table of information pertaining to the active layer will appear. For the "1938-1941 Photo Centers" layer, attributes for selected photographs include a link for viewing or downloading each file.
The user MUST specify the "active" layer to the "1938-1941 Photo Centers" layer.
|Clear Data Selection||Unselect all selected features.|
|Pan Map View||Drag the map image so that the area of interest is shifted within the view.|
|Previous Extent||Return the map view to the previous zoom level and location.|
|Zoom to Active Layer||Enlarge or reduce the map image to the fullest extent of the data layer selected to be the "active" layer.|
|Zoom to Full Extent||Zoom the map view out to the the fullest extent of all data layers, in this case, the boundary of the state of Illinois.|
|Print Map View||The user is prompted to submit a map title. After typing and submitting the title, a new window opens that contains a formatted title, map image, and legend suitable for printing. Use the browser "Print" button to print the map.|
|Legend or Layers||Toggle between the layer list and the map legend. The layer list enables the user to set the active data layer and also set the display of individual data layers to be on or off. The legend is a graphical representation of the symbology of all visible map layers.|