Application Of Direct Linear Transformation Method With Additional Constraint Conditions

With the rapid development of economy and technology,the construction of urbanization is accelerating,and many major municipal engineering projects have sprung up like bamboo shoots after the rain.At the same time,the quality of the urban construction will not be able to meet the requirements,so the problem of engineering safety has been emerging in an endless stream.At this time,the importance of deformation monitoring is self-evident,but the traditional methods of deformation monitoring have some limitations.Nowadays,as a branch of photogrammetry and remote sensing,close range photogrammetry has been widely used in deformation measurement because of its high efficiency and high precision measurement.And with the rapid development of science and technology and the wide application of computers,the surveyors can no longer be restricted by the special equipment.At the same time,the system errors in close range photogrammetry can be processed by more precise mathematical models.With the popularity of digital cameras and the maturity of technology,non metric digital cameras are more and more widely used in close range photogrammetry.The direct linear transformation method(DLT)is an algorithm to establish a direct linear relationship between the image point coordinates and the square space coordinate.It is especially suitable for the digital camera because it does not need the initial approximate value of the internal and external azimuth elements.Based on the above problems,this paper introduces the calibration of digital camera in three dimensional field,and restricts the classical DLT algorithm,thus improving the accuracy of the subsequent data.Then the experiment is carried out on the four line of Hefei Metro.The feasibility of this method is verified by comparing the data of the coordinates calculated by this model and the data of the coordinates calculated by bundle.