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UNIT 12 DOQQ - Geo4143 Remote Sensing of the Environment 1...

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1 Geo4143 Remote Sensing of the Environment Dr. Charles Roberts DIGITAL ORTHOGRAPHIC PHOTOS In the 1980s’ the USGS spearheaded an effort to coordinate the various agencies which were flying aerial photography, so that a single mission flown periodically would suite all. The USGS was striving to update the nations topographic maps every 5 years, and this photography was to be used for that purpose.The result was the National High Altitude Aerial Photography Program (NHAP) NHAP The footprint of the NHAP photography was the same as the USGS 1:24,000 scale 7.5 minute topographic quadrangle. It was flow between 1984 and 1986 in Leaf On condition at a scale of 1:58,000. These were the first CIR photographs available to the public. They were used to update the nations topographic maps. Generally, it was found that they were too low resolution for many uses, and a new mission was planned that would be higher resolution. It would be called NAPP NAPP (National Aerial Photography Program) Since NAPP would be flow at a higher resolution, it would have to be a subset of the topographic quadrangle. It s footprint would be one quarter of a quadrangle. It was flow in leaf off condition, because urban uses wanted to see through the tree canopy. It was also flown at a different scale, 1:40,000. The first missions were in the late 1980s, but Florida was not flown till 1995. These aerial photographs were flown over Florida in 1995, 1999 and 2004. They became the first three generations of Digital Orthographic Quarter Quadrangles (DOQQ s) when they are produced by the USGS, and DOP s when they are produced by other agencies. With the development of digital photogrammetric techniques, it has become possible to work with scanned, georectified aerial photographs. These are called Digital Orthographic Photographs (DOP) . The first entity to develop this product was the USGS, who scanned and rectified NAPP photography. Remember that NAPP photography is a mission that is flown to update topographic maps or Quadrangles, and that each NAPP photo covers one quarter of a 7.5 minute USGS topographic Quadrangle. Therefore, the digital USGS NAPP product is called a Digital Orthographic Quarter Quads (DOQQ) , and when four are sewn together to represent a topographic map, they are called a Digital Orthographic Quadrangle (DOQ ). They are the first "one meter resolution" data, and have now been joined by one meter resolution hyperspectral data and one meter resolution satellite data. They are revolutionizing GISystems, because many people who never used remote sensing products before are now using these. Since 1995, many different state agencies in Broward county have begun to create their own doqq’s through contracts with photogrammetric firms. These are called Digital Ortho Photographs (DOP’s). The current trend is towards higher resolution (ie, 6 inch, 1/3 foot) normal color imagery.
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2 Concepts and Terms Lets get the terms straight. What does orthophotography mean, and how can you remember it?
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