ABSTRACT:– The accuracy of photogrammetry can be increased with better instruments, careful geometric characteristics of the system, more observations and rigorous adjustment. The main objective of this research is to develop a new mathematical model of two types of linear features (straight line, spline curve) in addition to relating linear features in object space to the image space using the Direct Linear Transformation (DLT). The second main objective of the present paper is to study of some geometric characteristics of the system, when the linear features are used in close range photogrammetric reduction processes. In this research, the accuracy improvement has been evaluated by adopting certain assessment criteria, this will be performed by computing the positional discrepancies between the photogrammetrically calculated object space coordinates of some check object points, with the original check points of the test field, in terms of their respective RMS errors values. In addition, the resulting least squares estimated covariance matrices of the check object point’s space coordinates. To perform the above purposes, some experiments are performed with synthetic images. The obtained results showed significant improvements in the positional accuracy of close range photogrammetry, when starting node, end nodes, and interior node on straight line and spline curve are increased with certain specifications regarding the location and magnitude of each type of them.

KEYWORDS:– Accuracy -linear features – geometric characteristics- close range photogrammetry