This metadata record describes the acquisition and production of natural color digital orthoimagery for the state of Mississippi. The digital orthoimagery was composed of 24 bit natural color digital orthos at a scale of 1 to 400 with a 2' ground sample distance (GSD) for the project area. The SID images were created using a 20:1 compression ratio. This Mississippi Statewide orthophotography project was broken into 3 phases: Part A Acquisition, Part B Acquisition, and Processing. Part A Acquisition occurred January through March, 2006. Part B Acquisition occurred January, 2007. The Processing was broken into 2 phases: Part A and Part B. Part A aerotriangulation, digital elevation model, and digital orthophotography were completed by block. Part A consisted of 3 blocks. The following counties were processed within Part A and referenced to Mississippi State Plane East: Tishomingo, Alcorn, Tippah, Benton, Marshall, Prentiss, Union, Lafayette, Itawamba, Lee, Pontotoc, Monroe, Chickasaw, Calhoun, Lowndes, Clay, Webster, Oktibbeha, Choctaw, Noxubee, Winston, Attala, Kemper, Neshoba, Leake, Lauderdale, Newton, and Scott. The following counties were processed within Part A and referenced to Mississippi State Plane West: DeSoto, Tate, Tunica, Panola, Quitman, Coahoma, Yalobusha, Tallahatchie, Sunflower, Bolivar, Grenada, Montgomery, Carroll, Leflore, Holmes, Humphreys, Washington, Madison, Yazoo, Sharkey, Issaquena, Rankin, Hinds, and Warren. Part B aerotriangulation, digital elevation model, and digital orthophotography will follow the same processes as Part A; however, the final completion date of all processes is scheduled to be 7/30/07. The following counties will be processed within Part B and referenced to Mississippi State Plane East: Clarke, Jasper, Smith, Wayne, Jones, Covington, Green, Perry, Forrest, Lamar, George, Stone, Pearl River, Jackson, Harrison, and Hancock. The following counties will be processed within Part B and referenced to Mississippi State Plane West: Simpson, Copiah, Claiborne, Jefferson, Jefferson Davis, Lawrence, Lincoln, Franklin, Adams, Marion, Walthall, Pike, Amite, and Wilkinson. The following contributed to this Mississippi Statewide orthophotography project: EarthData International, Inc. Mississippi Geographic Information, LLC Mississippi Department Environmental Quality NOAA Coastal Services Center Mississippi DOT Mississippi State University Mississippi Coordinating Council for Remote Sensing and GIS
The acquisition and production of natural color digital orthoimagery covering the state of Mississippi will be packaged and delivered by county. The imagery may be used for cadastral (tax) or infrastructure mapping purposes.
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This data has been produced to be fully compliant with the National Standard for Spatial Data Accuracy (NSSDA) at a scale of 1 to 400.
Compliance with the accuracy standard was ensured by the collection of photo identifiable GPS ground control after the acquisition of aerial imagery. The following checks were performed. 1. The ground control and airborne GPS data stream were validated through a fully analytical bundle aerotriangulation adjustment. The RMSE is less than 1, 10,000th of the flying height. 2. The DEM data was checked against the project control. The technician visited and confirmed the accuracy of the points during initial processing. 3. Digital orthophotography was validated through an inspection of edge matching and visual inspection for image quality.
The following methods are used to assure imagery accuracy. 1. Use of IMU (inertial measurment unit) and ground control network utilizing GPS techniques. 2. Use of airborne GPS (global positioning system) in conjunction with the acquisition of imagery. The following software is used for validation of the imagery and surface modeling. 1. Aerotriangulation - ISTAR 2. DEM data - ISTAR 3. Digital Orthophotography - ISTAR, OrthoPro, and Photoshop. 4. Bentley - MicroStation 5. ISTAR 6. ESRI - ArcView, ArcMap 7. EarthData proprietary software 8. Adobe - Photoshop
This data has been produced to be fully compliant with the National Standard for Spatial Data Accuracy (NSSDA) at a scale of 1 to 400 with a 2' GSD.
The aerial imagery acquisition for the Mississippi Statewide project (Part A) was flown to support the creation of digital orthophotography with a 2' GSD. The imagery was acquired in 31 lifts consisting of 285 lines running east, west. The imagery was flown at 18,900 feet above mean terrain. Imagery was flown with a 30% overlap between flight lines. All imagery was collected using the Leica ADS40 digital pushbroom sensor.
Waggoner Engineering, Inc., under contract to EarthData International, Inc. successfully established ground control for the Mississippi Statewide project (Part A). A total of 43 ground control points in Mississippi were acquired using GPS for both vertical and horizontal coordinate values. All 43 points utilized photo identifiable points.
The U.S. Geological Survey has developed a National Elevation Dataset (NED). The NED is a seamless mosaic of best-available elevation data. The 7.5-minute elevation data for the conterminous United States are the primary initial source data. In addition to the availability of complete 7.5-minute data, efficient processing methods were developed to filter production artifacts in the existing data, convert to the NAD83 datum, edge-match, and fill slivers of missing data at quadrangle seams. One of the effects of the NED processing steps is a much-improved base of elevation data for calculating slope and hydrologic derivatives. The specifications for the NED Geographic coordinate system Horizontal datum of NAD83, Vertical datum of NAVD88, units of meters.
EarthData utilized an ISTAR workflow for processing the aerotriangulation (AT) for the orthoimagery covering the Mississippi Statewide project area (Part A). The airborne GPS data was processed and integrated with the inertial measurement unit (IMU). The resulting imagery and control were imported into the ISTAR system for use in the aerotriangulation. The ADS40 imagery was downloaded onto the EarthData server and brought over to the UNIX based ISTAR system. The ground control was used in conjunction with the processed airborne global positioning system (ABGPS) results for the AT. A total of 6 surveyed ground control points were not used (HV_B04 - This point was used only for elevation due to a possible survey error. HV_C01 - Point could not be measured because the stop bar blended into the dirt. HV_C02 - Not used because there were trees covering the point. HV_C04 - Not used because there were trees covering the point. HV_C05 - The newly poured concrete walkway surveyed was not there at the time of the flight. HV_D03 - Point could not be accurately measured due to building lean and the shadows from the building.). A total of 13 surveyed ground control points from previous 6" GSD projects were used (Tippah County, MS - 6 points; Lauderdale County, MS - 2 points; Clay County, MS - 5 points). The ground control points were read in all available imagery and tie points between flight lines were selected. A fully analytical bundle adjustment was run. The properly formatted ISTAR results were used for subsequent processing. All final results were output into an AT report. The AT for the Mississippi Statewide project (Part A) was completed by block. Part A consisted of 3 blocks. Block 1 AT was completed on 10/5/06. Block 2 AT was completed on 10/6/06. Block 3 AT was completed on 10/16/06.
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The NED was downloaded from the USGS website. Using the DEM data set, the technician verified that there were no voids, and that the data covered the project limits. The technician then selected a series of areas from the dataset and inspected them where adjacent flight lines met. Ground control point checks were performed on the NED to ensure the accuracy specifications were met. This DEM surface is used in the rectification of the orthoimagery. The DEM for the Mississippi Statewide project (Part A) was completed by block. Part A consisted of 3 blocks. Block 1 was completed on 11/16/06. Block 2 was completed on 11/7/06. Block 3 was completed on 12/13/06.
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The digital orthophotography is comprised of a 24 bit, natural color, 2' GSD ground orthos for the Mississippi Statewide project (Part A). The ISTAR process was used in the generation of the orthoimagery covering the Mississippi Statewide project (Part A). The initial radiometric adjustments were performed on the imagery for each flight line attempting to reach the best possible histogram. The rectification process was then run using the DEM surface and the radiometrically balanced imagery on each flight line. The quicklook (reduced resolution rectification) of each flight line exported out of ISTAR. A second set of radiometric adjustments were made using EarthData proprietary tools. The radiometrically balanced imagery was then re-imported into the ISTAR system and the histogram from the quicklook was applied to the full resolution imagery. Mosaic lines were placed, joining the ADS40 imagery strips. An initial QA/QC was performed by the technician to ensure that the mosaic lines were appropriately placed and that there was appropriate imagery coverage. The final imagery data set is removed from the ISTAR environment in a process called "packaging" where the individual tiles are created. It is during packaging that final datum and projection are defined (Mississippi State Plane East, NAD83/HARN, NAVD88, US Survey Feet). The created tiles are reviewed again for anomalies and interactive radiometric adjustment applied where needed. QA/QC was performed looking for anomalies, smears and other indications of problems within the digital orthophoto creation process, interactive radiometric adjustment applied where needed. Two additional radiometric adjustments are applied to the completed orthos in Adobe Photoshop. The first is a sharpening mask filter; this filter is used to help increase sharpness of a digital image. The basis for this filter is to locate pixels that differ in value from surrounding pixels by the threshold specified. It then increases the pixels' contrast by the value identified. For neighboring pixels specified by the threshold, the lighter pixels get even lighter and the darker pixels get even darker based on the specified amount. The changes made maintained the integrity of the original histogram curve. The final digital ortho product was GeoTIFF with TFW and a seamless mosaic for each county. All data was delivered on firewire. The digital orthophotos for the Mississippi Statewide project (Part A) was completed by block. Part A consisted of 3 blocks. Block 1 was completd on 1/30/07. Block 2 was completed on 12/20/06. Block 3 is scheduled to be completed by 2/27/07.
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143-A LeFleurs Square
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