A comparison between close-range computer mono-photogrammetry techniques for historical building documentation

Abstract

The purpose of this study was to compare the accuracy of documentation drawings produced by four computer close-range mono-photogrammetric techniques with that produced by hand measurements. It was hypothesized that there would no difference between Treatments (A, B, C, and D), size of dimensions (small, medium, and large), and orientation of dimensions (horizontal and vertical). The population for this research included dimensions on each of the four the documentation drawings of a commercial building. AutoCAD v12 contains a method of calibrating a digitizing tablet for flat plane photogrammetry. The print is digitized into the computer which corrects the photographic distortion by rubber-sheeting the drawing. After the elevation drawings were completed, a sample of 30 dimensions was selected and hand measured. For each treatment sample the same dimensions were electronically measured within AutoCAD software. Of the 120 observations all but 22 were within the expected tolerance. Analysis of Variance and the Hartley tests were used to test the three hypotheses. A significant difference was not detected between orientations. However, the ANOVA test detected a significant difference between the size of dimension groups. The ANOVA test did not find a difference between treatments. However, the Hartley test did identify a significant difference between Treatments B and C. The ANOVA test did not indicate an interaction between treatments, orientation, and/or size. Several recommendations are offered based on the results of this study. It is suggested that a study be conducted on a multi-story commercial building and compare the time and safety of photogrammetry to that of hand measuring. A comparison between traditional hand measured board drawings, hand measured computer drawings, and photogrammetric drawings for several different sizes of buildings should be performed. Further exploration into the digitizing process is recommended. Additional factors should be evaluated and tested. The factors would include the following: (a) higher resolution of the digitizing tablet, (b) larger negatives and larger prints, (c) other software packages, (d) the magnification used on the digitizing puck, and (e) the size of the hairline on the digitizing puck.