Two photogrammetric methods for measuring flat elements in buildings under construction

Usually, determining the dimensions of flat surfaces in buildings under construction, such as window cavities and façade coating materials, are done by direct measuring methods using tapes and plummets. Sometimes these methods suppose a slow and highly risky work for operators. This research proposes the substitution of these procedures by indirect methods based on close range photogrammetry and laser distance measurement. First, we show the design, construction and calibration of a system composed by a digital camera and a lasermeter mounted on a support with multiple turning positions. Next, two different façade element measuring methodologies are shown. The first method is based on taking a single photograph and measuring the distance to the object. The second one is based on taking three photographs and three distances measured at three different calibrated positions. Finally the accuracy of each methodology is analyzed and the pros and cons of each one are shown.