Modified Methods in Numerical Radial Triangulation

Two new modifications in numerical radial triangulation for extending horizontal control are presented. The first method, called the Method of Independent Stereopairs, involves computation of pass point coordinates for each independent stereopair in an arbitrary system. A strip is then formed by successively transforming each independent stereopair into the coordinate system of the first stereopair. The second method, called the Triplets Method, is similar but uses three adjacent overlapping photos as the basic computational unit. In each case the arbitrary strip coordinates are finally adjusted to ground control using a two-dimensional conformal coordinate transformation. The two methods have been tested using both fictitious and real photography of varying topography, scale, and tilt conditions. Results quoted for one representative strip of real photography indicate that with only a glass scale, paper prints, and a desk top computer, horizontal control can be extended to a fairly high degree of accuracy.