3.3. Precision and applicability
In general terms, the accuracy of a photo-based model depends
upon the scale and resolution of the input images, the distribution
and accuracy of control data (whether ground control points, scale
measurements or camera positions), the precision and distribution
of matched image points, and the network geometry, which includes
the number of photos, how much they overlap and how
convergent the views are. In close-range photogrammetry (e.g., as
often used for high accuracy engineering applications), where image
networks are usually multi-image and highly convergent, the
strength of a network can be described by its relative network
precision, which is a ratio of the mean 3D point uncertainty estimate
to the longest dimension of the network. For a given image
measurement precision, a stereo image pair with only two nearparallel
images would represent a weaker network than a convergent
multi-image arrangement. For projects using digital SLR imagery
covering sub-meter to kilometer scales processed with an
SfM-based approach, James and Robson (2012) estimated relative
precision ratios of ~1:1000 or greater. These ratios were shown to
be similar to those of theoretical estimates for stereo photogrammetry,
but approximately an order of magnitude poorer than
equivalent theoretical estimates for close-range (convergent)
networks.
3.3. Precision and applicabilityIn general terms, the accuracy of a photo-based model dependsupon the scale and resolution of the input images, the distributionand accuracy of control data (whether ground control points, scalemeasurements or camera positions), the precision and distributionof matched image points, and the network geometry, which includesthe number of photos, how much they overlap and howconvergent the views are. In close-range photogrammetry (e.g., asoften used for high accuracy engineering applications), where imagenetworks are usually multi-image and highly convergent, thestrength of a network can be described by its relative networkprecision, which is a ratio of the mean 3D point uncertainty estimateto the longest dimension of the network. For a given imagemeasurement precision, a stereo image pair with only two nearparallelimages would represent a weaker network than a convergentmulti-image arrangement. For projects using digital SLR imagerycovering sub-meter to kilometer scales processed with anSfM-based approach, James and Robson (2012) estimated relativeprecision ratios of ~1:1000 or greater. These ratios were shown tobe similar to those of theoretical estimates for stereo photogrammetry,but approximately an order of magnitude poorer thanequivalent theoretical estimates for close-range (convergent)networks.
การแปล กรุณารอสักครู่..