Coordinate Transformation

Offline Manolis Maragoudakis over 7 years ago

I am a little bit confused about how to apply a helmert transformation.

In the attached file i create two models. The TM3 west model which has an assigned coord system and the EGSA model which has a different coord system assigned.

Then i attach the TM3 model to the EGSA model and i choose Geographic - Reprojected as orientation.

So as you see in the EGSA model the TM3 model has been transformed to the new coord system.

In the EGSA file i have also with a red color the coords that the TM3 file should finally have.

So i usally do a helmert transformation between the temp "white coords" and the final "red" coords and i apply it to the temp white geometry.

I thought that if i set the computation helmert parameters in the coord system modifiers of EGSA file will do what i want but it doesn't.

What i am doing wrong?

0 Offline Manolis Maragoudakis Sat, Aug 20 2016 4:33 AM

coords test.dgn
Cancel
Vote Up 0 Vote Down

Sign in to reply

Verify Answer

Cancel
0 Offline Martin Roy Tue, Aug 23 2016 3:04 PM in reply to Manolis Maragoudakis
Hi. The elements of TM3 are being reprojected from TM3-West to GreekGRS87.GreekGrid when that model is attached to your EGSA model. The coordinate system defined in the main model (EGSA) serves as a label, so we know what system to reproject to, we do not apply a transformation to the main model.
If the elements don't fall in the right location once reprojected it might be because you are not using the right coordinate systems for that data ? You seem to say the data also requires an additional Helmert transformation, which means that it is not in the TM3-West model? Maybe you need to define your own custom coordinate system(s) if you are not working directly in those two ?
Cancel
Vote Up 0 Vote Down

Sign in to reply

Verify Answer

Cancel