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Los Alamos National Laboratory through the Regents of the University of California contracted and coordinated digital acquisition of six inch natural color digital orthophotography for an area covering approximately 140 square miles.The data were collected in July and August 2005. The bounding coordinates provided within the Spatial Domain section represent a rectangle in which the project is located. Data produced within this project boundary include orthophotography tiles base upon a modified grid tiling scheme defined by the client. Project tasks included: (1) Digital Aerial Imagery Acquisition Missing Planning; (2) Ground Control Surveys; (3) Digital Aerial Imagery Acquisition Mission; (4) Fully Analytical Aerial Triangulation; (5) Digital Terrain Model (DTM) Data Collection; (6) Final DTM Edit; and (7) Digital Orthorectified Imagery Generation. A total of 640 tiles of digital orthophotography were produced to cover the project area. Each final deliverable 0.5 foot resolution true color digital orthophotography tile measures 3000' x 2000'. Deliverables include: - 24-Bit True Color 0.5 foot resolution digital orthophotography tiles in GeoTIFF format - Associated tiff world files Digital True (Natural) Color aerial photography were acquired using an Intergraph Z/I Imaging DMC® (Digital Mapping Camera)-Serial # - DMC01-0002-proven accurate for photogrammetric mapping by the USGS digital sensor evaluation program at Stennis, Mississippi. The flight design achieved a nominal ground pixel resolution sufficient for developing 0.5 foot pixel orthophotography without oversampling. It was also designed with sufficient forward overlap and strip side laps to ensure total project area coverage according to the following flight specifications: Altitude: 4500' above mean terrain Focal Length: 120 mm (4.72") Imagery Scale: 1 "=950', (Photo Scale PS: 1:11,400) Conditions: Leaf Off, Cloud Free, Optimum Sun Angle Forward Overlap: 60% Sidelap: 30% Flight Lines: 24 Exposures: 1287 Control Panels: 6 In addition to airborne Global Positioning System (GPS) control and Inertial Measurement Unit (IMU) data, ground control points were acquired under the supervision of a registered surveyor at sufficient density and accuracy to support production of digital orthophotography to the specifications required. Control was collected in NM State Plane, Central Zone, NAD83, NAVD88, US Feet. Aerotriangulation was performed using industry-accepted procedures on approved softcopy workstation to support the horizontal accuracy requirements of the digital orthophotography-Root Mean Square Error (RMSE) of known ground points does not exceed 1 foot in x, y, or z. Surface data were constructed using industry-accepted procedures with sufficient density of points to support production of digital orthophotography according to the required specifications. Digital orthophotography was created using industry accepted procedures. The most nadir part of every image was used during Digital Orthorectification. Mosaic seam lines were created to ensure that joins do not cut hard detail where avoidable. Mosaic lines do not cross through above-ground structures unless unavoidable. Seams through or along streets were placed to avoid obscuring or artificially creating centerlines, curbs, and sidewalks. Compliance with the accuracy standard was ensured by the placement of photo identifiable ground control points and the collection of airborne GPS and IMU data. Meets National Map Accuracy Standards at 1" = 200' (1 :2,400); Meets American Society of Remote Sensing and Photogrammetry (ASPRS) Class 2 Standards for Large-Scale Maps (horizontal); All ground control adhered to the "Geometric Geodetic Accuracy Standards and Specifications for Using Relative Positioning Techniques", FGDC Version 5.0, of August 1, 1989, published by the Federal Geodetic Control Subcommittee (FGCS).The autocorrelated digital elevation model data were created from stereo model pairs using ImageStation Automatic Elevations software. Models were clipped, inventoried and ingested into a PostgreSQL database which is integrated into the workflow for the differential rectification of the digital orthophotography.The completed digital orthophoto tiles were checked for image quality. Quality control included assessment of every final tile in regard to positional accuracy, surface accuracy, and radiometric quality. Tiles were inspected against seam line placement to ensure that no hard detail was cut. Minor artifacts and adjustments were corrected using Adobe Photoshop in an interactive editing session.DMC data and accompanying GPS and IMU data were downloaded from hard disks and checked to verify that no files were corrupted and that all data could be downloaded. Digital aerial imagery that was used for this project included three-band (Red, Green, and Blue) images. The 12-bit image frames were inspected in an uncorrected state to verify the integrity of each flight line.Consistent project lookup tables (LUTs) for the 12-bit data were created using a gamma function and applied to each frame of photography. LUT applied frame data were then resampled from 12-bit to 8-bit format prior to orthorectification.Master color balancing was conducted across large areas of the project to create consistent tonal and color balance among adjacent image frames yielding a uniform overall appearance. Using master color balancing metadata, mosaic blocks were submitted to the mosaicking and tiling process. Final 24-bit natural color tiled output was inspected for data voids and radiometric integrity.Aerotriangulation for the project was accomplished using two AT blocks where the horizontal and vertical positions of all ground control points in each block were observed on the 12-bit imagery. Ground control, GPS and IMU information were ingested and tie points between flight lines were identified. ISAT produced the bundle adjustment. The results of the adjustment were verified for nominal accuracies to within 1 US Survey Foot. An ASPRS certified photogrammetrist inspected the aerotriangulation process for quality.The new 2 (two) foot DTM used in the orthorectification process on this project was created utilizing photogrammetric software to generate a gridded auto-correlated surface. DTMs created with this method conform to ASPRS Accuracy Standards for Class 2 large-scale mapping at a contour interval of 2.0 feet.Bohannan Huston Inc. established ground control to support the aerotriangulation process. A total of 24 surveyed points were paneled to support the AT process.
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