24.22.1. Combinations

The initial approximation is calculated by averaging out the combinations of calculated observations two by two whose error is less than the maximum admissible tolerance. This information can be viewed by the clicking the Combinations button. In addition to the coordinates obtained from each combination, the program shows the error associated with the averaging out process and the total average error. One can likewise modify initial approximation coordinates by changing the X Coordinate and Y Coordinate fields.
All the combinations can be activated, so that they are included in the calculation by clicking Select All, as well as deactivating them by clicking the Clear All button. Lastly, the Default button restores the original calculation observations, i.e. those whose error margins are within the tolerances set in the configuration. The Print button displays a list in the following format:
                                       
 
COMBINATIONS LIST
 
E1
E2
E3
X Coord.
Y Coord.
Error
S 11
S 12
927.257
1158.367
0.490*
 
S 11
S 6
927.487
1158.805
0.005
 
S 11
S 15
927.482
1158.797
0.005
 
S 11
S 16
927.463
1158.761
0.046*
 
S 12
S 6
927.485
1158.806
0.005
 
S 12
S 15
927.481
1158.798
0.005
 
S 12
S 16
927.462
1158.761
0.046*
 
S 6
S 15
927.587
1158.730
0.126*
 
S 6
S 16
927.638
1158.692
0.189*
 
S 15
S 16
927.660
1158.683
0.213*
 
 
X Average=927.484   Y Average=1158.801    Average Error=0.005
It can be seen that all the combinations are included. The ones used in the calculation are denoted by an asterisk (*). The X Coordinate and Y Coordinate boxes allow to directly enter the coordinates to be used for the initial approximation before the adjustment is performed. It must be remembered that the least squares adjustment method will normally find the optimum solution only if the initial approximation is not too far from the definitive one. At times, it may be necessary to change these values manually.