Georgetown County South Carolina Orthophotography, 17SPS225840

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In 2009 the county of Georgetown tasked Fugro EarthData in 2009 to fly and produce orthophotography. For that project a DSM was generated from Fugro EarthData's Pixel Factory processing software. The Pixel Factory digital surface modeling is based on an auto correlated pixel-matching system within the Pixel Factory software. The auto correlated digital surface model (DSM) surface represents the initial surface model. The following is the process used. 1. Using the DSM Pixel Factory data set created, the technician performed a visual inspection of the data to verify that the flight lines met correctly. The technician also 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. 2. This DSM surface is used in the rectification of the orthoimagery. | Type of Source Media: external hard drive

TerraSurv was contracted by the Fugro EarthData to acquire 36 ground control points during the acquisition of aerial imagery. The ground control points were established using GPS for vertical and horizontal coordinate values. NAD83(NSRS2007)South Carolina Stateplane NAVD 88 International Feet. | Type of Source Media: external hard drive

In 2008 Fugro EarthData flew lidar data over Marion and Dillon counties South Carolina for the South Carolina LiDAR Consortium. The data produced from that project was utilized as the surface for orthorectification. | Type of Source Media: external hard drive

The aerial imagery acquisition for Georgetown, Marion, and Dillon Counties was flown to support the creation of digital orthophotography with a 30cm pixel. The imagery was acquired on January 31st, and February 3rd, 7th, and 8th, 2010. There were four sorties and 50 flight lines. All imagery was collected using the Leica ADS40-52 digital pushbroom sensor. | Type of Source Media: not made available

The digital orthophotography is comprised of a 24 bit, natural color RGB bands, 30cm pixel resolution ground orthos for the 3 counties of the project. The Pixel Factory process was used in the generation of the orthoimagery covering all project tiles. 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 processed DSM and the lidar surfaces and the radiometrically balanced imagery on each flight line. The quicklook (reduced resolution rectification) of each flight line exported out of Pixel Factory. A second set of radiometric adjustments were made using Earthdata proprietary tools. The radiometrically balanced imagery was then re-imported into the Pixel Factory system and the histogram from the quicklook was applied to the full resolution imagery. Mosaic lines were placed, joining the ADS40 imagery strips. In 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 Pixel Factory environment in a process called "packaging" where the individual tiles are created. All data processing in the Pixel Factory system is performed in UTM Zone 17N meters; it is during packaging that final datum and projection are defined. 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 files. All data was delivered on external hard drives.