[PROJ] API migration - Offset on z-axis

[Kilian Demeulemeester]

Hello everyone.

Our team upgraded proj API from 4 to 6.

We noticed difference between the result when using projection in 
Switzerland (for instance EPSG:2056).

Here, I try to recap the difference between our implementation:

*Initial implementation (PROJ 4):*

// Input: x,y,z be coordinate expressed in EPSG:4978

projPJ pj_in;
projPJ pj_out;

pj_in = pj_init_plus("+init=epsg:4978");
pj_out = pj_init_plus("+init=epsg:2056");

pj_transform(pj_in, pj_out, 1, 1, x, y, z);

*Current implementation (PROJ 6)*

// Input: PJ_COORD coord expressed in EPSG:4978
PJ_CONTEXT* context = projContextCreate();
PJ* p1 = proj_create_crs_to_crs(context, "EPSG:4978", "EPSG:2056", NULL);
PJ* proj = proj_normalize_for_visualization(context, p1);
coord = proj_trans(proj , PJ_FWD, coord);

---


We noticed that the output using our current implementation yield the 
wrong result: there is an offset along the z-axis.

Are we doing something wrong?

Thank you very much.



Kilian Demeulemeester
Software Developer - R&D

[https://yellowscan-lidar.com/]

1 Chemin de fescau
34980 Montferrier-Sur-Lez - France
Tel: +33 (0)4 11 93 14 06
yellowscan-lidar.com [https://yellowscan-lidar.com/]
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