# CoordTrans - 2 local system

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

## CoordTrans - 2 local system

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

## CoordTrans - 2 local system

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.

## CoordTrans - 2 local system

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

## CoordTrans - 2 local system

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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applied-geodesy.org - OpenSource Least-Squares Adjustment Software for Geodetic Sciences