Resolution: 1.0 Meter

Band: 1-band: Panchromatic

USDA Agricultural and Commodity Stabilization ServiceBlack and WhiteScanned and georectified using ERDAS ImagineFlying height 40,000 feet, 6-inch focal length camera SRS: NAD83 HARN Delaware State Plane metersScale: 1:20,000

These are scanned images from aerial photography flown in 1954 by the Agricultural Stabilization and Conservation Service. The images are presented as a statewide mosaic. This aerial photography was scanned and georectified to provide a historic look at Delaware.

Scanning The original, paper format, 9x9" aerial photographs were taken in 1954 as part of an aerial survey program. The photographs were scanned at 300 dpi on an 11x17" EPSON GT-15000 scanner, as multi-band, RGB color images. The output was written to *.JPG files. The eastern half of Sussex County, however, was scanned as single-band, gray scale images, and the output was written to *.TIF files. Correcting for this data mismatch is described in the mosaicking section. Georectifying All georectifying was completed in ERDAS Imagine 8.7. Please see the included tutorial for a more detailed explanation. This document was used for training and reference by staff members completing the processing. 1. Ground control points (GCPs) were created on the 1954 images using the 2002 digital orthophotography of Delaware as a reference, using the Image Geometric Correction Tool. The 2002 data was produced in False Color Infrared at a scale of 1:2,400 with a 1 foot pixel resolution. This data is also available in a single, mosaicked MrSID file and is assigned a State Plane Coordinate System and a North American Datum of 1983. In eastern Sussex County, every attempt was made to create GCPs at a standard scale of 1:3,000, however, due to photo quality this scale was not always possible. For the remainder of the state, the largest scale possible was used while still maintaining a clear, unpixelated image on the screen. 2. The scanned images were then resampled to those points using the Display Resample Image Dialog. 3. The GCPs were stored for each image tile along with the Control Point Error from the registration process. 4. Resampled images (1954 corrected) were subsetted (i.e. cropped) to remove photograph borders, fiducial marks, and distorted edges. Mosaicking The 1954 aerial mosaic was created using ERDAS Imagine 8.7. Before the mosaic could be created, each multi-band image was reduced to a single band gray scale image, because the eastern half of Sussex County was georectified by another processor using images that were scanned as single-band, gray scale images. This was performed using ERDAS Imagine's layer stacking tool to create a new set of images containing only their first band. Once this new set of images was created the mosaic of the entire state could be processed. To complete this task, the mosaic tool from ERDAS Imagine was used and contained a feather technique for blending overlapping images. Holes in the final image of Delaware are due to misplacement of aerial photographs.

Resolution: 1.0 Meter

Band: 1-band: Panchromatic

USDA Agricultural and Commodity Stabilization ServiceBlack and WhiteScanned and georectified using ERDAS ImagineFlying height 40,000 feet, 6-inch focal length camera SRS: NAD83 HARN Delaware State Plane metersScale: 1:20,000

These are scanned images from aerial photography flown in 1954 by the Agricultural Stabilization and Conservation Service. The images are presented as a statewide mosaic. This aerial photography was scanned and georectified to provide a historic look at Delaware.

Scanning The original, paper format, 9x9" aerial photographs were taken in 1954 as part of an aerial survey program. The photographs were scanned at 300 dpi on an 11x17" EPSON GT-15000 scanner, as multi-band, RGB color images. The output was written to *.JPG files. The eastern half of Sussex County, however, was scanned as single-band, gray scale images, and the output was written to *.TIF files. Correcting for this data mismatch is described in the mosaicking section. Georectifying All georectifying was completed in ERDAS Imagine 8.7. Please see the included tutorial for a more detailed explanation. This document was used for training and reference by staff members completing the processing. 1. Ground control points (GCPs) were created on the 1954 images using the 2002 digital orthophotography of Delaware as a reference, using the Image Geometric Correction Tool. The 2002 data was produced in False Color Infrared at a scale of 1:2,400 with a 1 foot pixel resolution. This data is also available in a single, mosaicked MrSID file and is assigned a State Plane Coordinate System and a North American Datum of 1983. In eastern Sussex County, every attempt was made to create GCPs at a standard scale of 1:3,000, however, due to photo quality this scale was not always possible. For the remainder of the state, the largest scale possible was used while still maintaining a clear, unpixelated image on the screen. 2. The scanned images were then resampled to those points using the Display Resample Image Dialog. 3. The GCPs were stored for each image tile along with the Control Point Error from the registration process. 4. Resampled images (1954 corrected) were subsetted (i.e. cropped) to remove photograph borders, fiducial marks, and distorted edges. Mosaicking The 1954 aerial mosaic was created using ERDAS Imagine 8.7. Before the mosaic could be created, each multi-band image was reduced to a single band gray scale image, because the eastern half of Sussex County was georectified by another processor using images that were scanned as single-band, gray scale images. This was performed using ERDAS Imagine's layer stacking tool to create a new set of images containing only their first band. Once this new set of images was created the mosaic of the entire state could be processed. To complete this task, the mosaic tool from ERDAS Imagine was used and contained a feather technique for blending overlapping images. Holes in the final image of Delaware are due to misplacement of aerial photographs.