2012 Multispectral Color Orthophotography at .30m GSD, UTM z2S projection, GeoTIFF file format for American Samoa.

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Converted from FGDC Content Standard for Digital Geospatial Metadata (version FGDC-STD-001-1998) using 'fgdc_to_inport_xml.pl' script. Contact Tyler Christensen (NOS) for details.

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Exterior Orientation (EO) Parameters (x,y,z,omega,phi,kappa) were produced to provide precise photocenter locations for each frame of imagery. The two mission baseline information are as follows: August 2, 2012 minimum baseline length is 0.476km; maximum baseline length is 32.432km; and mean baseline length is 12.358km. August 3, 2012 minimum baseline length is 0.022km; maximum baseline length is 40.399km; and mean baseline length is 14.860km. Aerotriangulation was necessary to achieve the accuracy requirements of the project. | Source Geospatial Form: ASCII Text File | Type of Source Media: disc

Targeted ground control was collected for use in the Aerotriangulation process. Sixty-five (65) photo identifiable ground control points were selected and surveyed to adequately cover the entire state. Details of each point can be found in the full control report. | Source Geospatial Form: remote-sensing image | Type of Source Media: External Hard Drive

Photo Science developed classified, bare earth, .LAS LiDAR data at a 1-meter nominal post spacing with a fundamental 15 cm vertical accuracy at 95% confidence interval. Some areas of Ta'u were missing LiDAR so a stereocompiled DEM was created from the imagery. | Source Geospatial Form: vector digital data | Type of Source Media: External

Orthorectified images were geometrically corrected to achieve a uniform scale. Each frame was adjusted for topographic relief, lens distortion and camera tilt. | Source Geospatial Form: remote-sensing image | Type of Source Media: disc, DVD or online

The digital aerial imagery was obtained using a large format Microsoft Vexcel Ultracam. Aerial imagery was supplemented with the simultaneous acquisition of airborne GPS/IMU data, which captured the ground coordinate for the nadir point of each photograph. Aerial imagery was exposed at an altitude of 9,000' above mean terrain yielding an approximate GSD of 1 foot. A minimum of 70% forward gain and 40% sidelap was collected to ensure full stereo coverage. The aerial images are used in the production of orthophotos. | Source Geospatial Form: remote-sensing image | Type of Source Media: External Hard Drive

SoftCopy Aerotriangulation is a computer process of densifying the ground control network from locations in a few of the digital images to numerous points in each digital image that is to be used in the mapping process. This process is dependent on the location and coordinate positions of the ABGPS and GPS photo control points as well as a precise camera calibration for the Microsoft Vexcel Ultracam camera used to capture the images. | Source Geospatial Form: ASCII Report File | Type of Source Media: disc

The stereoimages are the product of the processed stereo imagery frames and the Aerotriangulation solution. Digital imagery was produced in TIF file format, 4-band, 8-bit stereo pairs. | Source Geospatial Form: remote-sensing image | Type of Source Media: External Hard Drive

The tile definition was used to cut orthorectified imagery into manageable, usable images in UTM projection. The UTM deliverables defined by this tile definition were modeled after the U.S. National Grid and references NAD83 UTM projection, units of Meters. Each tile is 1500 X 1500 meters. | Source Geospatial Form: vector digital data | Type of Source Media: disc

The tiled orthophoto was the result of mosaicking orthorectified imagery and using the tile definition to cut the data into manageable, usable orthophotos. 173 ortho tiles for delivery to USGS were created. | Source Geospatial Form: remote-sensing image | Type of Source Media: disc, DVD or online

Sixty-five (65) photo identifiable control locations were selected and surveyed to adequately cover the entire state. Details of each point can be found in the full control report. Accuracies of 10cm or better (horizontally and vertically) were required. | Source Produced: Georeferenced Aerial Imagery

New digital aerial imagery was obtained in the spring of 2012 using a large format Microsoft Vexcel Ultracam equipped with Airborne GPS/IMU. A total of 22 flight lines with 671 frames were collected in multispectral (RGB and NIR) 12 bits per band format. The imagery was acquired with a 100.5 mm focal length at an altitude of 9,000' above mean terrain, to yield a raw pixel resolution of 1' (.30 m) suitable for photogrammetric mapping and orthophoto production. The 'leaf condition' was not a concern but imagery was collected in the summer of 2012 under conditions free from flooding and excessive soil moisture. Within populated areas, no more than 5% clouds, cloud shadows, smoke, and haze are permitted. In the uninhabited areas of the islands 10% of clouds, cloud shadows, smoke, and haze may exist. There is no tide coordination. The sun angle threshold was 30 degrees. To ensure complete coverage, photography was collected for all tiles that intersected the islands of American Samoa (Tutuila, Aunnu'u, Ofu, Olosega, and Ta'u). Orthoimages were visually inspected for completeness to ensure that no gaps or image misplacements exist within and between adjacent images. | Source Produced: Raw Aerial Imagery

Imagery and AGPS/IMU data is downloaded from the hard drive on the plane to the hard drive on the ground. AGPS/IMU mission data is processed together with continuously collected ground-based CORS GPS base station data in forward and reverse directions. This precisely determines the aerial camera's position and orientation in the terrain (project) coordinate system and allows for correct orientation of the imagery. | Source Produced: Exterior Orientation File

The EOFILE, raw frames, and control points were input into ISAT in order to complete the SoftCopy Aerotriangulation, described in ATSOL source contribution, and assembled into a block. A second degree block adjustment is run along with the full least squares bundle adjustment. Once the last set of blunders and adjustments are complete, a final block bundle adjustment is run to produce the final solution. The final adjustment of the block is accomplished by using a rigorous simultaneous least squares bundle adjustment. The general procedure is to remove all blunders from the data using automatic blunder detection. The bundle adjustment is then run with minimal ground control to test the photogrammetric measurements for consistency. Next, the full ground control data set, including ABGPS data, is added to the adjustment. The horizontal control is then tightened and the effect on the vertical control and the photogrammetric residuals are inspected. The final adjustment makes sure that all of the measurements are in balance with each other and properly represent the actual conditions. | Source Produced: Stereo Imagery

The rectification process required as input a digital elevation model (LiDAR_DEM), imagery (IMG1) and soft copy aerotriangulation solution (ATSOL). The orthorectified imagery was produced using Intergraph Orthopro software. It used ImageStation Photogrammetric Manager (ISPM) for photogrammetry project setup, file management, and importing triangulation data from a user defined ASCII file (ATSOL). The ortho project records all the operations, including all the parameters that are defined through the OrthoPro workflow, such as the project area coordinates, pixel size, rotation angle, ISPM project and its unorthorectified source images, product areas (TLDEF) orthorectification settings, seamlines and so on. The results are single frame images that have yet to be mosaicked into manageable tiled orthos. The single frame orthos were checked for accuracy against the surveyed ground control before further image editing.

Orthorectified imagery was mosaicked, locally color-balanced and cut to the tile definition boundaries (TLDEF) using Intergraph Orthopro software. Tiled orthophotos then went through a rigorous manual QC process to evaluate for remaining hotspots (sun reflectance over water), tone quality, color balance and the feathering area along seamlines. Any imperfections at this point were manually edited. Clouds and cloud shadows were attempted to be minimized by using alternate views from adjoining frames. The tiled images were then converted to the required file format (GeoTIFF) and transferred to external hard drives for delivery to USGS. | Source Produced: Tiled Orthophoto