These data have not been geometrically corrected.
Statewide coverage of USDA-AAA aerial photographs was first achieved for Illinois from 1936 through 1941. Approximately 33,000 individual frames were acquired for complete coverage of the state.
Negatives of the prints for Illinois, and 12 other states, were destroyed at the National Archives sometime during the 1970's. No formal reason has been given by the National Archives to explain the destruction of the negatives. One possibility could be deterioration and stability issues of the original 7-inch by 9-inch and 9-inch by 9-inch nitrocellulose (silver nitrate) negatives. The United States Navy and the National Archives made small-format copies of the negatives prior to the destruction of the original negatives. So far, the prints that project staff have encountered, that were made from these small-format copies, have been of extremely poor quality. Therefore, photographic paper prints made from the original large-format negatives are the best remaining representation of this aerial photography collection.
Two, nearly complete, photographic paper print collections exist for Illinois. The first collection, originally at the Illinois Department of Natural Resources Office of Water Resources (IDNR OWR), is currently held at the Illinois State Library (ISL)). The second collection, is archived at the University of Illinois at Urbana Champaign (UIUC) Map and Geography Library. Smaller regional print collections are also located at many Illinois libraries and governmental agencies. None of the collections are complete, however, and only limited preservation efforts are in place to ensure the permanence of these print collections.
Any access to these data, Web sites, computer systems, electronic services, and electronic networks is governed by University and campus policies, in particular, but not limited to, the Policy on Appropriate Use of Computers and Network Systems at the University of Illinois at Urbana-Champaign, the ISGS Terms of Use document available at the ISGS Web site, and the University of Illinois Web Privacy Notice.
Links to these are provided in the Cross References section.
Individuals or entities may make fair use of copyrighted ISGS material, such as reproducing a single figure or table, or using a brief text quotation, without obtaining formal permission, but in all cases the Illinois State Geological Survey must be credited as the source of the material. To reproduce ISGS information beyond the fair use standard, permission must be obtained from the ISGS Information Office, 615 East Peabody Drive, Champaign, Illinois 61820, 217-333-4747, isgs@isgs.illinois.edu. License fees and a license agreement may be required, depending on the proposed usage.
Any use of these data is governed by University and campus policies, in particular, but not limited to, the Policy on Appropriate Use of Computers and Network Systems at the University of Illinois at Urbana-Champaign, the ISGS Terms of Use document available at the ISGS Web site, and the University of Illinois Web Privacy Notice. Links to these are provided in the Cross References section.
Map information is to be used at a scientifically and cartographically appropriate scale, that is, at a scale no greater than indicated on the map or as described in the documentation of the map or map data. Map information is not appropriate for, and is not to be used as, a geodetic, legal, or engineering base. Map information has no legal basis in the definition of boundaries or property lines and is not intended as a substitute for surveyed locations such as can be determined by a registered Public Land Surveyor.
The data do not replace the need for detailed site-specific studies.
Funding source: Institute of Museum and Library Sciences (IMLS) Funding source: Illinois Department of Transportation (IDOT) Funding source: Illinois Department of Natural Resources (IDNR) Funding source: IDNR Office of Water Resources (IDNR OWR) Funding source: United States Army Corps of Engineers (USACE) Funding source: Illinois State Geological Survey (ISGS) Funding source: Winnebago County Geographic Information System (WinGIS) Funding source: Lake County Department of Planning, Building and Development Funding source: JoDaviess County Soil and Water Conservation District (JoDaviess SWCD) Data automation: Deette Lund, Sheena Beaverson, project staff GIS processing: Deette Lund, Sheena Beaverson Documentation: Deette Lund, Donald Luman QA/QC: Deette Lund
PROJECT YEARS 2001-2005:Microsoft Windows 2000 Version 5.0 (Build 2195) Service Pack 4; MrSID Version 1.3.1.
PROJECT YEARS 2005-2007:Microsoft Windows XP Professional Version 2002 Service Pack 2; MrSID Version 5.0.6.1088.Bob_1055_br
PROJECT YEAR 2008:Microsoft Windows XP Professional Version 2002 Service Pack 2; MrSID Version 6.0.0.1331.Bob_1304_br
Quantitative testing of the image detail present on the paper emulsion of the prints was conducted to determine the optimum scanning resolution and grayscale range. It was found that little additional detail was gained by scanning at a resolution greater than above 750 dpi. An 8-bit grayscale range was sufficient to reproduce all of the information preserved upon each photographic paper print. If the original large-format film negatives were available, the images could have been digitized using higher dpi values at an increased grayscale range.
It is also imperative that each print in the collection be digitized only once to ensure cost effectiveness and minimize the exposure of each photographic paper print to the stresses of transport, preparation, handling, and digitization. An objective evaluation of several scanning systems was performed through a series of tests using a standard 20-step density wedge, circular target, fine gridlines, and an original 1938 aerial photography paper print. Based upon the results of this analysis, a Crosfield 646 IE drum scanning system was selected for the digitization procedures. The Crosfield scanning system was found to best maintain the original grayscale range and geometry of the original photographic paper print. Digitization procedures for these 45 counties within the ILHAP project were conducted by Scantech Color Systems, Inc. of Champaign, Illinois.
Photographs were scanned with the north direction oriented up. Counties flown west to east have annotation at the left side of the print. Counties flown north to south have annotation at the top of the print. The photographs possess an average of 60% endlap and 30% sidelap; adjacent photographs are suitable for stereoscopic viewing.
Due to a change in vendors a Crosfield Celsis 6200 drum scanning system was used for the digitization procedures. The Crosfield Celsis 6200 is an equipment upgrade from the Crosfield 646 that was used previously. The scanning quality remains the same. Digitization procedures for these thirteen counties within the ILHAP project were conducted by Martin Graphics of Champaign, Illinois.
Photographs were scanned with the north direction oriented up. Counties flown west to east have annotation at the left side of the print. Counties flown north to south have annotation at the top of the print. The photographs possess an average of 60% endlap and 30% sidelap; adjacent photographs are suitable for stereoscopic viewing.
The original scanned files are archived in TIFF format on CD-ROM at the Illinois State Geological Survey. The files available for download have been compressed using LizardTech's GeoExpress (Solaris platform) MrSID version 1.3.1 software at a compression ratio of 12:1.
No additional image processing will be imposed on these files to ensure the best preservation of existing feature details.
The original scanned files are archived in TIFF format on CD-ROM at the Illinois State Geological Survey. The files available for download have been compressed using LizardTech's GeoExpress (Solaris platform) MrSID Version 5.0.6.1088.Bob_1055_br software at a compression ratio of 6:1.
No additional image processing will be imposed on these files to ensure the best preservation of existing feature details.
Annotation example from file "0bwq04036.sid": 11-15-38 12:30 AAA SCALE 1:20,000 BWQ 4-36
11-15-38 = date (November 15th, 1938)
12:30 = time (12:30 pm Central Standard Time)
AAA = abbreviation for Agricultural Adjustment Administration
SCALE 1:20,000 = scale
(1 unit on the photo equals 20,000 units on the ground)
BWQ = county code (BWQ represents Cook County)
4-36 = film roll-exposure number (film roll = 4, exposure = 36)
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Illinois Natural Resources Geospatial Data Clearinghouse
Generated by mp version 2.8.25 on Thu Apr 16 11:22:29 2009