South Carolina DOQQ Archive
High-speed Viewing and Access to Digital Orthophotography via the Internet
December 31, 1999
A new Internet-based mechanism to distribute large quantities of orthophoto images was designed and implemented for the coast of South Carolina. The purpose of the system is to provide public access to a data stream that is in high demand, but is typically difficult to acquire and to distribute. Conventional HTML, Perl scripts and wavelett-based image compression were used to build the South Carolina DOQQ Archive.
Coastal planners and engineers frequently rely on geospatial information for management issues. Their requirements for rapid access to detailed spatial data over a large geographic area is especially acute in emergency management operations and large scale site assessment and permit applications. Orthoimagery is one of the most pertinent spatial data sources for these applications because it is easy to interpret, and is an excellent source map from which other data can be generated and integrated.
Orthoimagery is also one of the most challenging data sources to distribute economically because of the unusually large file sizes. Within the 8 coastal counties of South Carolina alone, there are over 500 separate images totaling over 86 gigabytes of data. Techniques that are commonly used today rely on tape, CD-ROM technologies and sometimes fee-based file transfer protocol. Typically these mechanisms do not allow previewing of the full data set prior to ordering. All of these conditions inhibit access and use of the orthoimagery, leaving coastal planners and engineers without some of their most basic data sources.
A new method of image compression is now available that allows for very large data sources (like orthoimagery) to be efficiently compressed.. The technique uses a wavelett compression algorithm that can reduce a typical 150 megabyte DOQQ to approximately 8.5 megabytes. By using a few Perl scripts, HTML, and freely available server software, an DOQQ archive was designed and built that can rapidity search, display and download data for the entire coastal South Carolina area using a conventional web browser.
Daniel Martin and Rong Lu : Technology Planning & Management Corporation
Cindy Fowler: Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration
Jim Scurry: Department of Natural Resources, State of South Carolina
Office of High Performance Computing and Communications, National Oceanic and Atmospheric Administration, U.S. DOC.
Special thanks to Dr. John Evans at MIT for technical assistance, and LizardTech Inc. for SID server code.
South Carolina Depatment of Natural Reasources - National Oceanic & Atmospheric Administration - Technology Planning & Management Corporation