by Marko 
, Monday, July 15, 2024, 07:34 (131 days ago)
Why do I get large transformation parameters when I want to do a 5-parameter Helmert transformation of 2 local 2D coordinate systems in CoordTrans? Identical points in both systems differ by 2-3cm, and the obtained transformation parameters move along the axes by 100-1000m.Parametars
Source system
Target System
by Micha 
, Bad Vilbel, Tuesday, July 16, 2024, 07:18 (131 days ago) @ Marko
Hi Marko,
in some cases, the centre of rotation is not inside but outside the network. This appears to be the case here. The cause is therefore your data or the configuration of your points.
/Micha
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applied-geodesy.org - OpenSource Least-Squares Adjustment Software for Geodetic Sciences
by Marko , Tuesday, July 16, 2024, 08:30 (131 days ago) @ Micha
Hi Micha
I have sent you my data, all the points are in the rectangle 15m x 270m. It is not clear to me why the center of rotation and translation would be outside that rectangle, especially since the differences between the two coordinate systems are small.
When I use say Leica Geo Office, I get normal transformation parameters of 2-3 cm.
by Micha , Bad Vilbel, Tuesday, July 16, 2024, 11:15 (130 days ago) @ Marko
Hi Marko,
When I use say Leica Geo Office, I get normal transformation parameters of 2-3 cm.
The different is the functional model. Most applications use a simplified functional model treating only the coordinates of the target system as observations. In JAG3D's CoordTrans both, the coordinates of the source and the target system, are treated as observations. CoordTrans addresses the most general case. So if you compare your results with other applications, make sure that all applications use identical algorithms.
/Micha
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applied-geodesy.org - OpenSource Least-Squares Adjustment Software for Geodetic Sciences
by Micha , Bad Vilbel, Tuesday, July 16, 2024, 04:23 (130 days ago) @ Marko
Hi Marko,
I have sent you my data,
I now had the time to take a look at the coordinates. Everything looks fine from my point of view. If you reduce your coordinates manually, the shift will be small. However, it is still the identical transformation, i.e. the weighted sum of squared residuals is (almost) identical, i.e., 5.84452183E-4 (reduced systems) vs. 5.84452188E-4 (original data). I'm not sure about your expectations, but large shift values are not an indicator of a poor transformation.
Kind regards
Micha
Here the reduced systems:
source.txt
R1.1 955.748 841.856 R1.2 939.741 817.587 R1.3 910.947 775.604 R1.5 851.444 694.252 R1.6 820.398 653.913 R1.7 795.972 622.823 R2.2 945.373 813.856 R2.3 916.452 771.794 R2.5 887.125 730.827 R2.6 856.820 690.199 R2.7 825.676 649.768 R2.8 806.988 625.956 R2.9 801.188 618.639 R3.2 961.670 827.155 R3.3 955.949 818.512 R3.4 950.564 810.361 R3.5 944.833 801.852 R3.6 938.964 793.273 R3.7 933.380 785.106 R3.8 927.523 776.679 R3.9 921.676 768.296 R3.10 915.895 760.139 R3.11 909.990 751.821 R3.12 903.919 743.374 R3.13 898.169 735.395 R3.15 892.114 727.108 RN3.16 885.988 718.766 RN3.17 880.078 710.800 RN3.18 873.926 702.550 RN3.19 867.727 694.275 RN3.20 861.766 686.406 RN3.21 855.612 678.318 RN3.22 849.293 670.068 RN3.23 843.276 662.206 RN3.24 836.977 654.123 RN3.25 830.632 645.939 RN3.26 824.575 638.168 R3.27 818.297 630.220 R3.28 811.868 622.091 R3.29 806.107 614.799
target.txt
R1.1 955.779 841.828 R1.2 939.767 817.559 R1.3 910.969 775.580 R1.5 851.444 694.232 R1.6 820.392 653.889 R1.7 795.966 622.804 R2.2 945.399 813.829 R2.3 916.466 771.778 R2.5 887.139 730.809 R2.6 856.814 690.181 R2.7 825.687 649.747 R2.8 806.978 625.935 R2.9 801.193 618.618 R3.2 961.700 827.123 R3.3 955.980 818.480 R3.4 950.591 810.331 R3.5 944.860 801.824 R3.6 938.987 793.245 R3.7 933.406 785.081 R3.8 927.544 776.651 R3.9 921.698 768.270 R3.10 915.915 760.115 R3.11 910.007 751.793 R3.12 903.935 743.348 R3.13 898.182 735.376 R3.15 892.128 727.088 R3.16 885.972 718.752 R3.17 880.063 710.789 R3.18 873.907 702.536 R3.19 867.705 694.259 R3.20 861.750 686.395 R3.21 855.593 678.301 R3.22 849.275 670.056 R3.23 843.259 662.192 R3.24 836.989 654.103 R3.25 830.616 645.928 R3.26 824.557 638.152 R3.27 818.280 630.203 R3.28 811.852 622.074 R3.29 806.090 614.780
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