When you balance angles, TPC divides the total angular error displayed in the Closure View by the number of control points included in the closing points and adds or subtracts this angle from each control point angle being adjusted. The angle turned at the Initial point is adjusted, along with the closing angle entered in the Closing Angle dialog.
For TPC to compute the angular error, you must tell it two things 1) the closing angle and 2) the correct bearing/azimuth that should result from the closing angle. You enter this information in the Closing Angle Dialog by choosing Edit |Closure Settings from the Closure View.
When you enter the closing angle, TPC adds the angle to the Closing point you've specified to compute a closing bearing/azimuth. You also enter the correct bearing/azimuth, usually by recalling two points that define the correct bearing (i.e. 21..17 would recall the bearing/azimuth from point 21 to point 17). The difference between these two is the angular error.
You don't have to be concerned about whether the angular error is positive or negative. TPC takes care of that and ensures that if you balance angles, the resulting computed closing bearing/azimuth will equal the correct bearing/azimuth.
Once the control points are adjusted any side shots originating from them are recomputed using the raw data.
You may want to check the results of modifying certain angles without applying a systematic angular error correction to all angles. This is particularly helpful when you have setups that you know have weak backsights. To edit certain angles, turn off all adjustments and make a note of the angular error displayed in the Closure View. Then return to the Traverse View, edit the angles you think are producing the error and return to the Closure View to check the closure. You will get a quick idea of how the angles you thought were weakest affect the closure of the traverse.
Note: We recommend that you become familiar with both the strengths and weaknesses of the different adjustment methods and how they might be affected by balancing or not balancing angles prior to the application of those adjustment methods.
TPC will not balance angles if raw data does not exist or if coordinates have already been balanced.
Curvature and Refraction
Applying a Scale Factor
Adjusting a Traverse
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