This dataset contains orthoimagery of Cortland County New York. This dataset was created as part of the contract to provide new natural color digital aerial imagery with airborne GPS-IMU control and ground surveyed control to develop and support 4 band (RGBIR) 8 bit orthos for portions of New York State. Based on the NYSDOP-2013-RFP leaf-off 12-inch imagery was to be captured for Cortland County.
Keystone Aerial Surveys of Philadelphia, PA was chosen as the vendor to capture the aerial imagery. Axis and Keystone planned the flight mission with a target GSD of 1.0' with an endlap of 60% and a sidelap of 30%. The Ultracam Eagle digital mapping camera (UCE) coupled with flight navigation systems and airborne GPS and inertial measurement units were flown at an approximate altitude of 15,100' above mean ground elevation. The image footprint of the Ultracam Eagle yields a image footprint size of 20,010 x 13,080 pixels, thereby capturing an average image footprint of 20,010' wide by 13,080' inline for a twelve inch pixel resolution. The aerial imagery for Cortland County was flown as part of the New York 2015 1-Foot Imagery Area. A total of 87 flight lines and 6,806 exposures were captured for this area between April 15, 2015 and May 9, 2015. Cortland County imagery was georeferenced by the New York Central aerotriangulation block. This subblock of AT had a total of 72 flight lines and 5,592 exposures.
Aerotriangulation for this photo mission was performed using Microsoft UltraMap AT software. Automatic tie point measurements were formulated and independent ground control points and airborne GPS were introduced to further refine the data. Please see the final aerotriangulation and survey reports submitted to the NYS Office of Information Technology Services, GIS Program Office for additional information on the aerotriangulation and ground control collection.
Once a suitable aerotriangulation solution was obtained the UltraMap Ortho module was used to produce the orthorectified imagery, terrain model, and seamlines. This module produces digital orthophotos using a pixel based matching algorithm which is derived from the Digital Terrain Model (DTM) and radiometrically balanced proprietary imagery. The orthorectified images are then mosaicked together into the final tiles to produce a very accurate and precise orthophoto. The State of New York provided Axis a tile grid shapefile with 2,350 tiles with a dimension of 2,000â€™ by 3,000â€™. Once the tiles were output they were then inspected in a final QA/QC process for overall image quality with all undesirable artifacts and errors corrected before delivery. Final edits to the seamlines and terrain model files were also performed. Once the tiles were corrected a final adjustment to the brightness and contrast was applied. In addition, the tiles were converted to JP2/J2W format at a 10:1 compression ratio with ESRI AUX and MapInfo TAB files.