GEOG 330 Chapter 6

GEOG 330 Chapter 6 - Photogrammetry GEOG330 What is...

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Photogrammetry GEOG330
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What is photogrammetry? ! = “the art & science of making accurate measurements by means of aerial photography” (Jensen, 2007:149)
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Photogrammetry applications ! From a single aerial photograph , it is possible to measure: " The scale of the photograph; and, " The height , length , area , perimeter , & tone/color of an object
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Photogrammetry applications ! From multiple stereoscopic aerial photographs , it is possible to obtain: " Precise planimetric ( x , y ) location ; and, " Precise height ( z ) of an object
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Flightlines of vertical aerial photography ! Individual aerial photographs are acquired at various exposure elevations along a flightline ! Stereoscopic overlap (endlap) is the overlapping of each photograph over the next in the flightline (typically 60%)
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Flightlines of vertical aerial photography ! A block of aerial photography is produced by photographing multiple flightlines by 20 – 30% ! This overlap is commonly referred to as sidelap
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Flightlines of vertical aerial photography ! Calculating the number of flightlines for a given study area
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Flightlines of vertical aerial photography ! Calculating the number photographs per flightline
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Geometry of vertical aerial photography ! A typical 9 x 9 in. panchromatic vertical photograph has eight fiducial marks located in the four corners and the center of the four sides ! The principal point (PP) of the photograph is the exact point on the Earth where the optical axis of the camera was pointed during the exposure PP CPP CPP
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Geometry of vertical aerial photography ! A conjugate principal point (CPP) is the transferred principal point from the previous or next photograph in the flightline
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Scale of vertical aerial photography ! The scale of a photograph can be calculated by comparing real world object size vs. photographic image size s = ab / AB ! When computing the scale, both the numerator and the denominator should be converted to the same units to get the representative fraction 1/5000 or 1:5000 # ! ground covered but " detail captured 1/250000 or 1:250000 # " ground covered but ! detail captured
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Scale of vertical aerial photography !
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GEOG 330 Chapter 6 - Photogrammetry GEOG330 What is...

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