In this method, (Figure 8.3) a random line such as BQ is being laid such that R is visible from Q. A perpendicular QR is being erected at Q and measure its distance. Then the desired distance BR is being calculated using distance formula.
In laying the line BR, intermediate points are established first. These are laid by taking offset from the random line at distances calculated by using the method of similar triangle such as
After locating the intermediate points on the line BR, the obstructions get cleared to make the end points intervisible. Then, direct ranging is being carried out to obtain an extended continous straight line.