[PROJ] Helmert transform

[Lesparre, Jochem]

Hi Dean,

Do you use existing parameters for the Helmert transformation or do you estimate parameters yourself?

The quality and residuals of estimated parameters depends on the quality and distribution of the coordinates used for the estimation. For a Helmert transformation between a triangulated and a GNSS data set of an entire country of some hundreds of kilometres across, residuals over 1 metre are not uncommon. For two datasets of permanent GNSS stations of a small area, residuals can be under 1 centrimetre.

Kind regards, Jochem


Van: PROJ <proj-bounces at lists.osgeo.org> Namens Dean Howell
Verzonden: woensdag 20 maart 2019 06:01
Aan: proj at lists.osgeo.org
Onderwerp: [PROJ] Helmert transform

Hello all,

We have a project that is using the helmert transformation and we are trying to get an understanding of what level of residuals is acceptable and how we interpret the results.

If anyone has experience in using the helmert transformation, I would be interested in your feedback.

Regards

Dean Howell


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