Influence of Raw Image Preprocessing and Other Selected Processes on Accuracy of Close-Range Photogrammetric Systems According to Vdi 2634

Abstract

ABSTRACT:This paper examines the influence of raw image preprocessing and other selected processes on the accuracy of close-range photogrammetric measurement. The examined processes and features includes: raw image preprocessing, sensor unflatness, distancedependent lens distortion, extending the input observations (image measurements) by incorporating all RGB colour channels, ellipse centre eccentricity and target detecting. The examination of each effect is carried out experimentally by performing the validation procedure proposed in the German VDI guideline 2634/1. The validation procedure is based on performing standard photogrammetric measurements of high-accurate calibrated measuring lines (multi-scale bars) with known lengths (typical uncertainty = 5 µm at 2 sigma). The comparison of the measured lengths with the known values gives the maximum length measurement error LME, which characterize the accuracy of the validated photogrammetric system. For higher reliability the VDI test field was photographed ten times independently with the same configuration and camera settings. The images were acquired with the metric ALPA 12WA camera. The tests are performed on all ten measurements which gives the possibility to measure the repeatability of the estimated parameters as well. The influences are examined by comparing the quality characteristics of the reference and tested settings.

Flat Versus Hemispherical Dome Ports in Underwater Photogrammetry

“…The effect of chromatic aberrations in close range photogrammetry has been investigated mainly for high precision photogrammetric applications where the effect of separate image measurements for each colour channel can lead to a significant accuracy enhancement of a factor about 1.3 (Luhmann et al, 2006). Other rigorous methods that consider a colour or multi spectral dependent calibration and processing are discussed in (Reznicek et al 2016;Robson et al, 2014;Matsuoka et al, 2012). Optical aberrations in underwater photography are much more severe and difficult to correct with respect to those generally seen for regular cameras above the water.…”

Focus stacking photogrammetry for micro‐scale roughness reconstruction: a methodological study

“…Considering the results of the synthetic tests, it was decided to use the camera positioning as in subset IV with the following settings: (a) 30 partially sharp images to reconstruct one extended DOF image; (b) sum of extended DOF images -15; (c) a camera-to-surface angle of about 60°; (d) a relative aperture of f/8; (e) an exposure time of 0Á8 s; (f) an ISO of 100; and (g) a white balance of 6500 K lamp colour temperature. According to Reznicek et al (2016), a typical RAW to JPEG conversion does not result in a noticeable decrease in reconstruction accuracy. The output images were taken as JPEGs generated directly by the camera with the JPEG quality set to fine.…”