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Change detection of tooth surface loss in the cervical region of a tooth replica has been performed using a fixed-base stereoscopic camera, consisting of two SLR digital cameras with lenses of fixed focal length. Commercial digital photogrammetric and calibration software was used to perform a convergent multi-station calibration with an artefact comprising a transilluminated planar array and a tiered object exhibiting optical texture. Digital surface models of a tiered test object and a tooth surface containing a non-carious cervical lesion were generated from stereo-imagery. The accuracy of automatic mass point measurement of a planar surface was 4 ± 13 μm in Z. The sensitivity of change detection on mapped tooth replicas was 0·03 mm with change ranging from 0·03 to 0·07 mm per annum. Different rates of change were clearly evident in different areas at different times. The results of this investigation suggest that annual change detection studies will provide a clearer picture of the pattern of tooth surface loss and, in combination with other analytical techniques, a more detailed explanation of the natural history of these lesions. 相似文献
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Tyas Mutiara Basuki Andrew K. Skidmore Patrick E. van Laake Iris van Duren Yousif A. Hussin 《国际地球制图》2013,28(4):329-345
A main limitation of pixel-based vegetation indices or reflectance values for estimating above-ground biomass is that they do not consider the mixed spectral components on the earth's surface covered by a pixel. In this research, we decomposed mixed reflectance in each pixel before developing models to achieve higher accuracy in above-ground biomass estimation. Spectral mixture analysis was applied to decompose the mixed spectral components of Landsat-7 ETM+ imagery into fractional images. Afterwards, regression models were developed by integrating training data and fraction images. The results showed that the spectral mixture analysis improved the accuracy of biomass estimation of Dipterocarp forests. When applied to the independent validation data set, the model based on the vegetation fraction reduced 5–16% the root mean square error compared to the models using a single band 4 or 5, multiple bands 4, 5, 7 and all non-thermal bands of Landsat ETM+. 相似文献
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Commercial digital photogrammetric software has been applied to convergent stereoscopic photography of human tooth replicas prepared to exhibit optical texture resulting in successful generation of 3D coordinate data. Tooth replicas were imaged using a semi-metric 35 mm camera and f = 100 mm macro lens on extension bellows. Model precision was within acceptable limits of 12 μ m or better for manual target matching and 21 μ m or better for automatic image matching. Further improvement in optical texture is required to achieve automatic image matching precision comparable to that of manual target matching. Small errors in interior orientation parameters attributed to instability in the bellows as well as small errors in the relative orientation resulted in some systematic errors. The use of a fixed camera lens system is expected to reduce these errors. When combined with commercially available, moderately priced, digital SLR cameras this brings 3D model generation closer to everyday clinical dental practice. 相似文献
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