[PROJ] How to apply Helmert trafo

classic Classic list List threaded Threaded
2 messages Options
Reply | Threaded
Open this post in threaded view
|

[PROJ] How to apply Helmert trafo

Fabian Gross
Dear proj-members,

I would like to apply a Helmert trafo as part of a datum shift.
The example follows the EPSG geomatics guidance 7/2 (report 373-7-2):

From WGS72 (4984) -> WGS84 (4978).

There are 2 issues:
1. How to apply Helmert-Trafo? I.e.
  • with or
  • without the push/pop of the ellipsoidal height.
Only if it is not pushed/popped do the values fit to the reference and the direct/naive implementation of Helmert.
2. The scale parameters in the example (0.219) and the EPSG catalogue of pyproj (0.2263)  do not agree.

The attached file has the test case.


Kind regards

Fabian Gross
Telefon +49 (711) 648 71-995

_________________________________________________

sbp

schlaich
bergermann partner


Beratende Ingenieure
für erneuerbare Energie

Stuttgart . Berlin . New York
São Paulo . Shanghai . Paris

sbp sonne gmbh


Markus Balz Dipl.Ing. (FH)
Andreas Keil Dipl.Ing.

Schwabstrasse 43
70197 Stuttgart
Telefon +49 (711) 648 71-0

www.sbp.de
_________________________________________________

_______________________________________________
PROJ mailing list
[hidden email]
https://lists.osgeo.org/mailman/listinfo/proj

how_to_helmert.py (6K) Download Attachment
Reply | Threaded
Open this post in threaded view
|

Re: How to apply Helmert trafo

Jochem

Dear Fabian,

 

For this transformation push/pop is not needed. That only makes sense in other situations, like when you use a geoid.

 

If the scale factor also differs from the primary source (EPSG is a secondary source), it should be adapted in the example to avoid confusion. If EPSG differs with the primary source, EPSG should be notified that there might be a mistake in their registry.

 

Kind regards, Jochem

 

From: PROJ <[hidden email]> On Behalf Of Fabian Gross
Sent: Friday, June 14, 2019 3:41 PM
To: [hidden email]
Subject: [PROJ] How to apply Helmert trafo

 

Dear proj-members,

I would like to apply a Helmert trafo as part of a datum shift.
The example follows the EPSG geomatics guidance 7/2 (report 373-7-2):

From WGS72 (4984) -> WGS84 (4978).

There are 2 issues:
1. How to apply Helmert-Trafo? I.e.

  • with or
  • without the push/pop of the ellipsoidal height.

Only if it is not pushed/popped do the values fit to the reference and the direct/naive implementation of Helmert.
2. The scale parameters in the example (0.219) and the EPSG catalogue of pyproj (0.2263)  do not agree.

The attached file has the test case.


Kind regards

Fabian Gross
Telefon +49 (711) 648 71-995

_________________________________________________

sbp

schlaich
bergermann partner


Beratende Ingenieure
für erneuerbare Energie

Stuttgart . Berlin . New York
São Paulo . Shanghai . Paris

sbp sonne gmbh


Markus Balz Dipl.Ing. (FH)
Andreas Keil Dipl.Ing.

Schwabstrasse 43
70197 Stuttgart
Telefon +49 (711) 648 71-0

www.sbp.de
_________________________________________________



Disclaimer:
De inhoud van dit bericht is uitsluitend bestemd voor geadresseerde.
Gebruik van de inhoud van dit bericht door anderen zonder toestemming van het Kadaster
is onrechtmatig. Mocht dit bericht ten onrechte bij u terecht komen, dan verzoeken wij u
dit direct te melden aan de verzender en het bericht te vernietigen.
Aan de inhoud van dit bericht kunnen geen rechten worden ontleend.

Disclaimer:
The content of this message is meant to be received by the addressee only.
Use of the content of this message by anyone other than the addressee without the consent
of the Kadaster is unlawful. If you have received this message, but are not the addressee,
please contact the sender immediately and destroy the message.
No rights can be derived from the content of this message.

_______________________________________________
PROJ mailing list
[hidden email]
https://lists.osgeo.org/mailman/listinfo/proj