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Tyrrell County, NC 2007 Digital Orthos

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Abstract: Tyrrell County, North Carolina, published true color ortho imagery with 0.5-foot resolution over urbanized areas. The full county was captured and published at 1.0-foot resolution in a separate dataset. This dataset was developed to provide a spatially accurate, high resolution imagery to be used in the creation of other data layers. This Aerial Photography layer is also a primary base layer.
Purpose: An orthoimage is remotely sensed image data in which displacement of features in the image caused by terrain relief and sensor orientation have been mathematically removed. Orthoimagery combines the image characteristics of a photograph with the geometric qualities of a map. For this dataset, the orthoimages were produced at a 1.0 foot pixel resolution for all of Tyrrell County, North Carolina, with a 0.5 foot pixel resolution within Columbia and along the more developed areas along Albemarle Sound. Aerial photography was acquired on dates of February 24th and March 4th of 2007.
Supplemental Information: Aerial photography was acquired utilizing Leica (Wild) RC-30 film cameras. Camera Serial # 5282 with lens # 13328 was used for 1"=2000'scale photo capture of flight lines 1 through 6 on March 4th, 2007. The USGS calibration for camera # 5282 is dated July 21, 2006. Camera Serial # 5320 with lens # 13364 was used for 1"=2000'scale photo capture of flight lines 7 through 10 and 1"=1000' scale photo capture of flight lines 11 through 16 on February 24, 2007. The USGS calibration for camera # 5320 is dated March 17, 2003. The 1"=2000'photography was acquired at a target altitude of 12,000 feet Above Mean Terrain (AMT) and the 1"=1000'photography was acquired at a target altitude of 1"=6000' AMT. Mean Terrain of ~20 feet ASL was used for flight planning. 10 parallel flight lines were accomplished with a north-south orientation for the 1"=2000' scale using a minimum sidelap of 30% between flight lines with an exposure endlap of 60%. 6 parallel flight lines were accomplished with an east-west orientation for the 1"=1000' scale using a minimum sidelap of 30% between flight lines with an exposure endlap of 60%. During the time of image acquisition, two dual frequency geodetic grade GPS receivers were utilized. One receiver was operated on board the aircraft with the dual frequency antenna location calibrated to the Leica RC-30 camera. The second receiver was used as a base station located at the Elizabeth City, NC airport (ECG) north of Tyrrell County NC: ~ latitude N36.26 longitude W-76.17 at about elevation 12 feet MSL. These receivers were in constant operation during the photography mission and GPS phase data was collected at an epoch rate of 1 second. All GPS data was post processed as NC State Plane Coordinates North American Datum 1983(86), US Survey feet. Data from The Airborne GPS was used in combination with pre photo mission paneled NCGS ground monuments to control the photography. A total of 12 existing NC Geodetic Survey monuments were paneled with an acceptable distribution around the perimeter and across the County. All twelve of these paneled monuments have published NC State Plane coordinates in NAD 1983(86). In addition, 44 panels were placed with a driven rebar around and within the County as checkpoints. These were surveyed by GPS with data post processed using Trimble Pathfinder Office software. These "checkpoints" were not included within the initial analytical Triangulation (AT) computations that were based upon Airborne GPS and the paneled NCGS monuments. These 44 checkpoints were then used to check and confirm the horizontal precision of the AT adjustment. The checkpoints all matched the AT within 4 feet RMSE in the 1"=400' scale mapping areas and within 2.1 feet RMSE in the 1"=200' scale mapping areas. Aerial photography acquisition was accomplished with a minimum sun angle of 33 degrees. Two twin engine Piper Aztek Model PA 23-250 were used for aerial photo acquisition. Bounding coordinates for final Orthophotography in NC State Plane NAD 1983(86) US Survey feet (1 meter = 3.2808333 feet) are West 2760000; East 2910000; North 840000; and South 680000. Cloud Cover during aerial photo acquisition was less than 5%.
Publication Date: 2007
Originator: Tyrrell County Government
Publisher: Atlas Photogrammetric Data, PC
Time Period of Content:
Time Period Information:
Single Date/Time:
Calendar Date: 200702 to 200706
Currentness Reference: Ground Condition.
Progress: Complete
Maintenance and Update Frequency: Unknown
Spatial Domain:
Bounding Coordinates:
West Bounding Coordinate: -76.43640
East Bounding Coordinate: -75.92655
North Bounding Coordinate: +36.02335
South Bounding Coordinate: +35.58633
Contact Electronic Mail Address: GIS website: none
Contact Voice Telephone: (252) 796-1371
Horizontal Datum Name: North American Datum of 1983(86), US Survey feet (1 meter = 3.2808333 feet).
Planar Distance Units: US Survey Feet
Ellipsoid Name: Geodetic Reference System 80, see GEOID03 for GEOID Height calculation.
Map Projection Name: Lambert Conformal Conic
Attribute Label: ObjectID
Attribute Definition: Internal Feature Number
Attribute Definition Source: ESRI
Attribute Domain Values:
Unrepresentable Domain: Sequential unique whole numbers that are automatically generated.
Distribution Liability: Although care has been taken in preparing the information contained in this data, Tyrrell County does not guarantee the accuracy thereof. Anyone using the data does so at their own risk and shall be deemed to indemnify Tyrrell County from any and all injury and/or damage arising from such use. This data may not be resold.
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