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projects > creation of a digital archive of historical aerial photographs for everglades national park and the greater everglades ecosystem > work plan
Project Work Plan
Greater Everglades Science Program: Place-Based Studies
Project Work Plan FY 2003
A. GENERAL INFORMATION:
Project Title: Creation of a Digital Archive of Historical Aerial Photographs for Everglades National Park and the Greater Everglades Ecosystem
Other Investigator(s): Ann Foster, John Jones
Project Summary: A foundation for Everglades restoration must include a clear understanding of the pre-drainage south Florida landscape. Knowledge of the spatial organization and structure of pre-drainage landscape communities such as mangrove forests, marshes, sloughs, wet prairies, and pinelands, is essential to provide potential endpoints, restoration goals and performance measures to gauge restoration success Information contained in historical aerial photographs of the Everglades can aid in this endeavor.
The earliest known aerial photographs, from the mid to late 1920s, and resulted in the production of T-Sheets (Topographic Sheets) for the coasts and shorelines of south Florida. The T-Sheets are remarkably detailed, delineating features such as, shorelines, ponds, and waterways, in addition to the position of the boundary between differing vegetation communities. If followed through time changes in the position of these ecotones could potentially be used to judge effects of changes in the landscape of the Everglades ecosystem, providing a standard by which restoration success can be ascertained.
Participants at a recent "Performance Measure Workshop," sponsored by Everglades National Park, realized the importance of translating the Park's aerial photo archives into digital format. The value they represent to the Greater Everglades research community for developing a pre-drainage baseline is great. Investigators from all four USGS Divisions, the National Park Service, the South Florida Water Management District and the Florida Coastal Everglades LTER program have all expressed interest in such a collection when the initial concept was proposed at the recent International Estuarine Research Federation meeting in St. Petersburg.
Project Objectives and Strategy: The overall objective is to create a digital archive of historical aerial photographs of Everglades national park and surrounding area of the greater Everglades and south Florida. The archive will be in readily available Geographic Information System formats for ease of accessibility. Each set of photos (defined above) will be broadly disseminated to client agencies, academic institutions and the general public via Open-File Reports and through the Internet.
Potential Impacts and Major Products: The major products will be a series of USGS Open-File Reports, one for each complete, or near complete, set of photos. A photoset is defined as a collection of aerial photos that were taken during a discrete time, generally 30-60 days, with the same scale, film type, and camera. All OFRs will be distributed on CD-ROM. Each report will encompass a photoset with descriptive text sections such as Introduction, Metadata & Procedures, Study Area, and Acknowledgements. All scanned images will be in a downloadable format. One OFR (#02-0204), entitled "Conversion of Historical Topographic Sheets (T-sheets) to Digital Form: Florida Everglades and Vicinity," with digital copies of the 1927 topographic sheets has just been approved for release and another with the 1940 aerial photoset is under review. The products are being used in the formulation of Performance Measures. For example, spatial data on the movement of the mangrove / marsh ecotone (derived from the digital historical aerial photographs) will be used to provide a pre-drainage baseline of the Everglades ecosystem and metrics of success in restoration.Collaborators: Bill Perry, Everglades National Park
B. WORK PLAN
Title of Task 1: A digital archive of historical aerial photographs for south Florida.
Task Summary and Objectives: The overall objective is to create a digital archive of historical aerial photographs of Everglades national park and surrounding area of the greater Everglades and south Florida. The archive will be in readily available Geographic Information System formats for ease of accessibility. Each set of photos (defined above) will be broadly disseminated to client agencies, academic institutions and the general public via Open-File Reports and through the Internet.
Work to be undertaken during the proposal year and a description of the methods and procedures: The work will be accomplished using standard GIS software packages such as ERDAS, ARC/INFO and ARC/VIEW (use of trade names does not constitute endorsement by the USGS).
Scanning: At each software initialization settings will be established and / or verified. Scanning resolution may be determined by multiple factors, including the end needs of the user, processing constraints, storage space, and photo quality. Higher resolution photos (e.g. the 1987 photoset) may result in better output, but will require increased scan time, larger storage requirements (400-500 CDROMs) and increased processing and georeferencing time (see below). For example, we estimate that bringing the 1987 photoset to the rectification stage at a scan resolution of 300 dpi will take eight weeks.
A transparent template will be used to orient the photographs and eliminate the need to preview each individual image. Scanning will take approximately 3 minutes or longer per image. Following scanning the image will be archived. Files will be saved to an external storage medium. The original image file will be cropped to the area of interest as needed.
Rectification: Rectification will be accomplished via an ortho-rectification process using ERDAS OrthoBase or OrthoBase Pro software. This software depends on camera calibration reports that are readily available for later photosets, but not earlier ones. For the earlier photosets we will use a Non-Metric Camera Model. However, with knowledge of the camera (focal length, camera type) and the calibration reports, we will be able to extract the information necessary to construct a Frame Camera Geometric Model for the later photosets.
With a minimum number of Ground Control Points (GCPs) specified the software automatically collects "tie" points. The tie points will be manually examined and those with obvious error eliminated. GCPs will be distributed across the area being rectified to minimize distortion. For the region being studied, good ground control points are rare and poor GCPs are better than no GCPs. Wherever possible we will use known GCPs and may collect field GPS readings for identifiable locations in earlier photosets that are extant today such as canals, levees, and structures. We will use Digital Ortho-photo Quadrangle Quarters (DOQQs) as the reference data set for rectifying each scanned image. An image(s) will be matched with the appropriate DOQQ. By the use of DOQQs, we can use good GCPs from one image to assist in rectifying an adjacent image with few or no GCPs. It is still critical to have a minimum number of good GCPs.
Sampling error will be assessed by use of the triangulation report produced by OrthoBase. This report provides the Root Mean Square Error (RMSE) for each group of images. We will not accept rectification results high RMSE. Rectification will be an iterative process as GCPs are added and/or removed until the RMSE is within the desired level.
The final phase of rectification involves resampling the image and exporting the resultant, corrected (rectified) image to GEOTIFF format. The GEOTIFF images will be archived to external media.
Time Requirements: At present we have 26,625 individual frames of aerial photography from the Everglades National park archive. These are divided into approximately 11,000 paper prints and 15,000 transparencies. They are of different dimensions and scales. We estimate that at 300 dpi (a minimum standard) it will require 5 minutes for actual scanning (set-up, scan, save to file, organize directories and archive) and 30 minutes for rectification (pre-processing, locating photo vicinity / DOQQ, select and/or modify ground control points, resample, QA/QC, export corrected image to GEOTIFF format). The National park Service, who is currently funding the work, has required scanning at 800dpi, therefore the time required has increased considerably.
Planned Outreach: Participate in Open House activities at the Center for Coastal and Regional Marine Studies and the Florida Caribbean Science Center. Assist with Everglades National Park's annual Interpretive Naturalist training. Make both oral and poster presentations at appropriate scientific forums. Provide semi-annual briefings to appropriate staff from our client agencies.
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