"Seventeen (17) QC points were used in the ortho rectification process. All of the QC points were at well-defined locations and used in the aerotriangulation solution. The locations of the 17 QC ground points were compared to their positions on the rectified ortho images. The resulting X and Y residuals were used to calculate the NSSDA horizontal accuracy at the 95% confidence level in feet." {{ preceding citation from metadata prepared by project contractor Aero-Metric, Inc. }}
"Approximately fourteen hundred digital images were aerotriangulated to support digital ortho image production for the following five Wisconsin counties: Ozaukee, Dodge, Washington, Waukesha, and Milwaukee. Airborne GPS data was provided by AERO-METRIC, Inc. The project was referenced to the North American Datum of 1927 (NAD27), state plane Wisconsin south coordinate system horizontally and to the National Geodetic Vertical Datum of 1929 (NGVD29) vertically. Units were in feet."
"The images, ABGPS data, ground checkpoint data, and camera calibration data were used as inputs to the Zeiss/Intergraph ImageStation Automatic Triangulation (ISAT) softcopy program. ISAT correlated image points and aerotriangulated the block of images to create exposure station exterior orientations. Atmospheric refraction, and earth curvature were taken in to account during the aerotriangulation process. Seventeen ground checkpoints were manually measured on the imagery. These ground checkpoints were included in the aerotriangulation adjustment as unconstrained points for absolute ground location verification."
"The scale of the aerial IMAGEs was 1 inch = 2117 feet. An Intergraph Z/I Imaging DMC camera was used to aquire color aerial photography with 70% front overlap on 4/20/2007 and 4/21/2007."
"Rectification was done using the aerotriangulation data, scans, and DEM. These rectified images were used to draw seamlines. The images were then dodged. The dodged rectified images were mosaicked, balanced, and cut into final image sheets. The final sheets were viewed and artifacts were removed as well as other edits performed." {{ preceding citation from metadata prepared by project contractor Aero-Metric, Inc. }}
On April 14, 2008, new aerial photography was acquired for a small area of downtown City of Milwaukee. The new photography was obtained to correct an area of excessive building lean on the 2007 imagery. The area of 2008 imagery is roughly bounded by Clybourn and Michigan Streets on the south, I-43 on the west, Juneau and State Streets on the north, and Prospect Avenue and Lake Michigan on the east in downtown Milwaukee. The new imagery was incorporated into the 2007 orthophotography in early May 2008 by the project contractor and reviewed by the SEWRPC staff.
Each color GeoTIFF (Tagged Image File Format) file covers a 10,000 by 10,000 foot area or "tile" on the Wisconsin State Plane Coordinate System, South Zone. Each color image file is approximately 286 megabytes in size. The pixel resolution of the images is twelve inches (12") on the ground, with zero overlap between adjacent images. The orthophoto files are named according to the Wisconsin State Plane Coordinate System easting coordinate and northing coordinate, in thousands of feet, of the southwest corner of the image. Each image file includes an accompanying ESRI-format "world" file (".tfw" file extension) containing the coordinate information used to display and register the image in ESRI software. The orthophoto files were prepared to meet National Map Accuracy Standards (NMAS) for one-inch-equals-200-feet scale (1" = 200' scale) mapping. The entire set of 385 color GeoTIFF format files is approximately 110 gigabytes in size.
The color MrSID (Multi-Resolution Seamless Image Database) format files were prepared from the GeoTIFF format files. Each MrSID file covers approximately one U.S. Public Land Survey System (USPLSS) survey township. Each image file is approximately 160 megabytes in size. The pixel resolution of the images is twelve inches (12") on the ground, with a minimum of 500 feet of image extending beyond the survey township boundaries. The files are named with the township and range number of the survey township. Each image file includes an accompanying ESRI-format "world" file (".sdw" file extension) containing coordinate information used to display and register the image in ESRI software. The entire set of 36 color MrSID format files is approximately 4.5 gigabytes in size.