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Digital Ortho Image Creation of Hall County Aerial Photos
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Digital Ortho Image Creation of Hall County Aerial Photos


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Powerpoint Presentation that I presented at the Florida Academy of Science and Georgia Academy of Science Joint Conference held in Jacksonville, FL March 14th and 15th of 2008

Powerpoint Presentation that I presented at the Florida Academy of Science and Georgia Academy of Science Joint Conference held in Jacksonville, FL March 14th and 15th of 2008

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  • 1. Authors: Michael Adams Patrick Taylor J.B. Sharma Institute of Environmental Spatial Analysis
  • 2. The Hall County National Resource Conservation Service (NRCS) has several sets of historic aerial imagery The purpose of this project was to digitize these images such that the public can utilize them for perpetuity This project outlines the methods used in digitizing, geo-referencing, ortho-rectifying, and mosaicking a set of thirty-five images taken October 12, 1980 This project was made possible by support from the Institute of Environmental Spatial Analysis at Gainesville State College and from a grant provided by the Georgia View Consortium
  • 3. It is of utmost importance to preserve the vast number of vintage aerial photographs that have been taken over the last century These air photos are a clear recollection of the land as it was at that moment in time We can use this data to increase our understanding of key features of the land, including forests, watersheds, agricultural, and urban areas The ability to use this imagery to study temporal changes of land has grown tremendously as the technology and software has advanced
  • 4. approximately 394 square miles of land split by the Chattahoochee River and Lake Sydney Lanier. Population of193,277 according to the 2000 U.S. Census
  • 5. Set of 35 Aerial images from the Hall County NRCS taken by Harris Aerial Surveys Inc. All reference Images from the Georgia Spatial Data Infrastructure (GSDI) 1. 2 meter resolution National Agriculture Imagery Program (NAIP) Hall County Mr.sid file 2006 leaf on image 2. 1999 Digital Elevation Model with a 30m resolution
  • 6. Hard Copy 1 Digitizing 2 Georeferencing 3 Finished Ortho- Product 5 Mosaicking 4 Rectificaton
  • 7. Converting an analog image into a digital format Images scanned at 300 dots per inch(dpi) Each image was 24” x 24” We outsourced this part of the project to a local commercial printing company because we needed a large format scanner to handle this size imagery
  • 8. Assigning Representation of the coordinates of a X, Y, and Z planes standard geographic reference system to a geographic feature. In the X and Y Planes The X, Y, and Z planes are perpendicular to one another
  • 9. To correct an aerial photo for topographic relief, lens distortion, and camera tilt; to make the image true to scale as if it were a map Ortho corrected images are corrected for changes in the Z plane
  • 10. A sports stadium in downtown Toronto before and after rigorous orthorectification (Imagery courtesy of DigitalGlobe) Image Distortions
  • 11. Autosync Extension of Erdas Imagine 9.1 Direct Linear Transform method: This method creates Ground Control Points between Spatial Coordinates and Image Coordinates
  • 12. Corresponding GCP’s
  • 13. Hall County DEM used for correction of distortions in the Z plane
  • 14. Generated Cutlines
  • 15. Smoothing Filter applies a blurring filter along each side of the newly generated cutlines Feathering Filter softens the edges of the cutline by blending all of the pixels within a fixed distance Color Balancing removes brightness variations found across the mosaic Histogram Matching creates a new histogram for all of the images to be mosaicked by matching them to one another
  • 16. Image is ready for use in a GIS system for land use analyses or other research
  • 17. 1. Digitization of Images 1. Professionally scanned 2. Data Management 2. Created standard file structure 3. Computing power 3. Each image 350MB or > final mosaic 4.24 GB (Terabyte server) 4. Root Mean Square Error 4. Use .5 pixel error and swipe tool to visually interpret error 5. Mosaic 5. Mosaic lighting conditions/lens flare color balancing, histogram transition from image to matching image created cut-lines for feathering & smoothing filters
  • 18. Seams Visible Image Hot Spot
  • 19. Project Funded by a grant from The Georgia View Consortium These images are now useful for scientific analyses The Hard Copy of these images are now preserved for future generations
  • 20. Questions Please …
  • 21. Aronoff, Stan, 2005, Remote Sensing for GIS Managers, ESRI Press, Redlands, California, 487 p. Marzan, G. T. and Karara, H. M. 1975. A computer program for direct linear transformation solution of the colinearity condition, and some applications of it. Proceedings of the Symposium on Close-Range Photogrammetric Systems, pp. 420-476. American Society of Photogrammetry, Falls Church. 2007, Erdas Imagine 9.1 Field Guide Volume One, Leica Geosystems Geospatial Imaging, LLC, (March 7, 2008). 2007, Erdas Imagine 9.1 Field Guide Volume Two, Leica Geosystems Geospatial Imaging, LLC, (March 7, 2008). Kwon, Y.-H. (1994). KWON3D Motion Analysis Package 2.1 User's Reference Manual. Anyang, Korea: V-TEK Corporation. (March 12, 2008).