of the emitters within the coordinate system of the receiver the known distance between the emitters the known distance between the emitters and the pointer tip a point 8 is then drawn representing the calculated location of the front pointer tip 2 and a vector 9 is drawn representing the pointer direction the vector is the result of creating a line between the 2 emitters captured on an image and then extending it to the calculated pointer tip fig7 can then be used to estimate the amount of adjustment required to position the front pointer tip so that it is perfectly aligned with the center of rotation first the center of rotation can be estimated since it is by definition at the center of all the determined tip points once the center is estimated then the real adjustment to the pointer tip 2 position can be determined as shown in fig8 as can be seen in fig8 the adjustments can be determined from any of the data points as long as errors are calculated in a coordinate system that is aligned with the vector corresponding to the point once the front pointer tip is adjusted a subsequent data set can be collected and analyzed to ensure that the tip was properly adjusted examples of possible gantry misalignment shown in relation to pointer position captured on video are depicted on fig1 a 11 a and 12 a examples of corresponding vectors 9 which would be created for each of these misalignments as the result of analysis of the images taken during gantry rotation are shown on fig1 b 11 b and 12 b an added benefit of this new design is that the process of determining the gantry rotation with the signal emitting front pointer not only positions the.