[PROJ] Transformation for local grid

[Lesparre, Jochem]

Hi Pierre,

Your horizontal transformation is in geographic (angular) coordinates. So you have to do that before the projection to coordinates in metres.

Regard, Jochem


From: PROJ <proj-bounces at lists.osgeo.org> On Behalf Of Pierre Chaponniere
Sent: maandag 10 februari 2020 10:11
To: proj at lists.osgeo.org
Subject: [PROJ] Transformation for local grid

Dear all,

I am struggling to elaborate a pipeline with proj v6.3 that would transform lat long coordinates to a local grid system.
From what I see, I have all the required parameters, so I did a 3 step pipeline :

1/ transform from lat long wgs84 to projected using tmerc.

2/ run horizontal transformation which is a rotation around an origin - I was thinking of using the the Molobadekas transform for this purpose

3/ vertical shift for which I have an origin as well, east and north slope entries in ppm - i still need to figure how I'll pass this one...

So my proj line so far looks like this :

proj +proj=pipeline +step +proj=tmerc +lat_0=-1.90 +lon_0=115.90 +y_0=538.374 +x_0=5200.27 +ellps=GRS80 +step +proj=molobadekas +convention=coordinate_frame +x=-9.85881089465147 +y=-0.172038726321603 +s=17.60710142 +rz=1485.3205006576768028 +px=5225.30897756133 +py=-830.070127940344

But I keep on having errors as 'malformed pipeline' or 'non-angular input coordinates'...
Even trying to pass the Molobadekas transform on its own, I struggle...

Do you see anything that I am doing totally wrong here ?
Would be really appreciated to have your insight on this !

Thanks heaps,

Best regards,

Pierre C




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