SURVEY Subject Trimble Survey Controller Software: Problems in Resection Without Redundancy Product(s) Trimble® S6 Total Station, Trimble VXTM Spatial Station, 5600, 3600, and GDM600 total stations Question When I use the resection program with 2 backsight points, measured topo points are sometimes not calculated as I would expect, and the station point also seems to be wrong. What could be wrong? Answer There is unfortunately no redundancy in the configuration when you are using the resection program with 2 backsight points only. This means that some errors cannot be detected in the stationing result.Some explanations are shown in the following two examples. Backsight points changed by mistake  Two backsight points are given, BP1 and BP2:If you are measuring correctly to these backsight points, the station point Snom will be correct. If the backsight points coordinates are correct, you will not get any residuals. If a topo point is measured afterwards, it will be calculated at the correct position Pnom.However, when you change both points by mistake, for example, by calling the point BP1, but measuring to BP2, and vice versa, then: The station coordinates will be wrong: You will get the position Scalc. The rest of the result is the same as before. There are no residuals and the standard deviation is excellent or even zero. All points measured afterwards will be wrong, for example, the point Pcalc. Coordinates changed by mistake Sometimes coordinates are given in the wrong order. If the order is changed by mistake, the backsight points from the first example will be given as shown in the following example:  The station location is incorrect. Measured points and the staked object will be misplaced.To make sure that you are aware of such a fault as soon as possible, you must measure more backsight points: When you have measured the third point, it will be clear that something is wrong as this point will not fit with the former solution at all. Related Articles Trimble Survey Controller: Advantages of Redundancy in Station SetupTrimble Survey Controller: Task of the Stationing ProgramsTrimble Survey Controller: Orientation Parameter in Station SetupTrimble Survey Controller: Scale Factor in Station SetupTrimble Survey Controller: Purpose, Advantages, and Objectives of Resection Setup |