There are three scales of orthos: 1"=100' - orthos in this series have a ground resolution of 0.25x0.25 feet from color aerial photography taken at an approx scale of 1:7200 during the Spring of 2006. 1"= 200' - The orthos in this series have a ground resolution of 0.50x0.50 feet from color aerial photography taken at an approx scale of 1:14400 during the Spring of 2006. 1"=400' - The orthos in this series have a ground resolution of 1.00x1.00 feet from color aerial photography taken at an approx scale of 1:14400 during the Spring of 2006.
See processing steps for more information.
For 1"=100' The accuracy of the data input was sufficient to produce orthophotos that meet National Map Accuracy Standards for 1"=100' orthophotography. For 1"=200' The accuracy of the data input was sufficient to produce orthophotos that meet National Map Accuracy Standards for 1"=200' orthophotography. For 1"=400" The accuracy of the data input was sufficient to produce orthophotos that meet National Map Accuracy Standards for 1"=400' orthophotography.
The National Map Accuracy Standards stipulate that 90% of all well defined features not be displaced in excess of 1/30 inch for scales larger than 1:20,000
The camera calibration report provides the focal length of the camera and the distances in millimeters from the camera optical center reference for spatial measurements made from the photograph. The camera used for the source photography was a Wild RC30 equipped with forward motion compensation. The calibrated focal length for this camera at the time of photography was 152.193mm. Camera serial number: 5231. Lens serial no. 13246. Photography was flown on 03/04/06, 03/05/06 and 3/07/06
Ground control points were acquired from recovered monuments and GPS ground surveys and are Second Order Class 2 or better. This accuracy meets National Map Accuracy Standard (NMAS) for 1"=100' scale mapping. Ground control points are on the North Carolina State Plane Coordinate System 1983 North American Datum (NAD83/2001 adjustment). Analytical triangulation was performed to extend the horizontal and vertical ground control. A combination of photo center coordinates obtained through airborne GPS and ground control points were used for control of the analytical triangulation. Aerotriangulation was performed by softcopy methods using KLT Atlas software. Scans produced from the original film were used. A minimum of three passpoints were marked along the center of the stereo overlap area. One point near the center or nadir point of the photo and one point near each corner of the stereo model. These corner passpoints also served as tie points between strips. Point measurements were performed by softcopy methods using KLT Atlas software. A fully analytical simultaneous bundle adjustment was performed by a weighted least squares adjustment method using KLT Atlas aerotriangulation software. The root-mean-square error of passpoints computed in the analytical triangulation does not exceed one-fiftieth (1/50) of the denominator of the final map scale. The vertical accuracy does not exceed 1/10,000 of the flight altitude.
The raster image file was created by scanning the aerial film with a Leica DSW600 scanner with an aperture of approximately 10 microns. This equates to a ground resolution of 0.25 foot from the 1:7200 scale photography.
The DEM/DTM data was obtained by enhancing LiDAR data using softcopy photogrammetry methods. The seventy percent overlap raster images were viewed in 3D on KLT Atlas softcopy stereo systems. Breaklines were compiled as needed for orthophoto rectification where the change in terrain was in a linear form, such as along a stream bed, a road edge, a retaining wall or a ridgeline. DEM points were added manually where needed. Each stereo model was reviewed for completeness and accuracy by a second stereo operator before being used in the orthophoto rectification process. The vertical accuracy of the DEM/DTM is only sufficient to support the rectification of the aerial images and is not intended for contour generation.
All of the above mentioned inputs were used by experienced photogrammetry technicians in order to complete the orthorectification process. Orthophotos were rectified using KLT Atlas software which is capable of pixel-by-pixel rectification. Cubic convolution was the resampling method used. Final tone and contrast adjustments were completed using a combination of KLT Atlas, OrthoVista and PhotoShop software.
200 Scale Imagery: The rectification process requires input from a user parameter file to control the rectification process, camera calibration and aerial triangulation information, a digital elevation model (DEM/DTM) with the same area of coverage as the digital orthophoto, and an unrectified raster image file acquired from scanning the aerial film. These inputs were used collectively to register the raw image file mathematically to determine the location of the camera position and orientation with respect to the ground and to remove the relief displacement from the image file.
The camera calibration report provides the focal length of the camera and the distances in millimeters from the camera optical center reference for spatial measurements made from the photograph. The camera used for the source photography was a Zeiss Jena LMK equipped with forward motion compensation. The calibrated focal length for this camera at the time of photography was 152.179mm. Camera serial number: 272299c. Lens serial no. 7390598D. Photography was flown on 03/04/06, 03/05/06 and 3/07/06
Ground control points were acquired from recovered monuments and GPS ground surveys and are Second Order Class 2 or better. This accuracy meets National Map Accuracy Standard (NMAS) for 1"=200' scale mapping. Ground control points are on the North Carolina State Plane Coordinate System 1983 North American Datum (NAD83/2001 adjustment). Analytical triangulation was performed to extend the horizontal and vertical ground control. A combination of photo center coordinates obtained through airborne GPS and ground control points were used for control of the analytical triangulation. Aerotriangulation was performed by softcopy methods using KLT Atlas software. Scans produced from the original film were used. A minimum of three passpoints were marked along the center of the stereo overlap area. One point near the center or nadir point of the photo and one point near each corner of the stereo model. These corner passpoints also served as tie points between strips. Point measurements were performed by softcopy methods using KLT Atlas software. A fully analytical simultaneous bundle adjustment was performed by a weighted least squares adjustment method using KLT Atlas aerotriangulation software. The root-mean-square error of passpoints computed in the analytical triangulation does not exceed one-fiftieth (1/50) of the denominator of the final map scale. The vertical accuracy does not exceed 1/10,000 of the flight altitude.
The raster image file was created by scanning the aerial film with a Leica DSW600 scanner with an aperture of approximately 10 microns. This equates to a ground resolution of 0.50 foot from the 1:14400 scale photography.
The DEM/DTM data was obtained by updating previously compiled data using softcopy photogrammetry methods. The seventy percent overlap raster images were viewed in 3D on KLT Atlas softcopy stereo systems. Breaklines were compiled as needed for orthophoto rectification where the change in terrain was in a linear form, such as along a stream bed, a road edge, a retaining wall or a ridgeline. DEM points were added manually where needed. Each stereo model was reviewed for completeness and accuracy by a second stereo operator before being used in the orthophoto rectification process. The vertical accuracy of the DEM/DTM is only sufficient to support the rectification of the aerial images and is not intended for contour generation.
All of the above mentioned inputs were used by experienced photogrammetry technicians in order to complete the orthorectification process. Orthophotos were rectified using KLT Atlas software which is capable of pixel-by-pixel rectification. Cubic convolution was the resampling method used. Final tone and contrast adjustments were completed using a combination of KLT Atlas, OrthoVista and PhotoShop software.
400 Scale Imagery: The rectification process requires input from a user parameter file to control the rectification process, camera calibration and aerial triangulation information, a digital elevation model (DEM/DTM) with the same area of coverage as the digital orthophoto, and an unrectified raster image file acquired from scanning the aerial film. These inputs were used collectively to register the raw image file mathematically to determine the location of the camera position and orientation with respect to the ground and to remove the relief displacement from the image file.
The camera calibration report provides the focal length of the camera and the distances in millimeters from the camera optical center reference for spatial measurements made from the photograph. The camera used for the source photography was a Zeiss Jena LMK equipped with forward motion compensation. The calibrated focal length for this camera at the time of photography was 152.179mm. Camera serial number: 272299c. Lens serial no. 7390598D. Photography was flown on 03/04/06, 03/05/06 and 3/07/06
Ground control points were acquired from recovered monuments and GPS ground surveys and are Second Order Class 2 or better. This accuracy meets National Map Accuracy Standard (NMAS) for 1"=400' scale mapping. Ground control points are on the North Carolina State Plane Coordinate System 1983 North American Datum (NAD83/2001 adjustment). Analytical triangulation was performed to extend the horizontal and vertical ground control. A combination of photo center coordinates obtained through airborne GPS and ground control points were used for control of the analytical triangulation. Aerotriangulation was performed by softcopy methods using KLT Atlas software. Scans produced from the original film were used. A minimum of three passpoints were marked along the center of the stereo overlap area. One point near the center or nadir point of the photo and one point near each corner of the stereo model. These corner passpoints also served as tie points between strips. Point measurements were performed by softcopy methods using KLT Atlas software. A fully analytical simultaneous bundle adjustment was performed by a weighted least squares adjustment method using KLT Atlas aerotriangulation software. The root-mean-square error of passpoints computed in the analytical triangulation does not exceed one-fiftieth (1/50) of the denominator of the final map scale. The vertical accuracy does not exceed 1/10,000 of the flight altitude.
The raster image file was created by scanning the aerial film with a Leica DSW600 scanner with an aperture of approximately 10 microns. This equates to a ground resolution of 0.50 foot from the 1:14400 scale photography.
The DEM/DTM data was obtained by updating previously compiled data using softcopy photogrammetry methods. The seventy percent overlap raster images were viewed in 3D on KLT Atlas softcopy stereo systems. Breaklines were compiled as needed for orthophoto rectification where the change in terrain was in a linear form, such as along a stream bed, a road edge, a retaining wall or a ridgeline. DEM points were added manually where needed. Each stereo model was reviewed for completeness and accuracy by a second stereo operator before being used in the orthophoto rectification process. The vertical accuracy of the DEM/DTM is only sufficient to support the rectification of the aerial images and is not intended for contour generation.
All of the above mentioned inputs were used by experienced photogrammetry technicians in order to complete the orthorectification process. Orthophotos were rectified using KLT Atlas software which is capable of pixel-by-pixel rectification. Cubic convolution was the resampling method used. Final tone and contrast adjustments were completed using a combination of KLT Atlas, OrthoVista and PhotoShop software.
NOTE: For Data Organization, there were different pixel/cell sizes depending upon scale. Cell Size X and Y direction for 100 scale was 0.250000. Cell Size X and Y direction for 200 scale was 0.500000. Cell Size X and Y direction for 400 scale was 1.000000.