[Qgis-user] What QGIS plugin development should I work on this year?

[Gabriel De Luca]

Case 1) would be welcome.

I do a little manually that transformation. I convert the values of
latitude, longitude and ellipsoidal height to geocentric Cartesian
coordinates. Then I find the transformation parameters between the local
system and the geocentric one.

The transformation pipeline is then made up of: a 3D affine transformation
from the local to the geocentric system, the conversion from the geocentric
to the geodetic or geographic system, and finally the projection to some
cartographic system (usually a custom one, but can be projected to any).

The geoscience plugin, on the other hand, is based on the construction of a
derived from a projected reference system. In other words, it calculates
the affine transformation parameters in 2D between a local system and a
projected one and uses them in the construction of a new derived system. The
derived from projected CRS is only compatible with the WKT2:2019 version,
and that limits it in some GDAL and QGIS functions.

I collaborated with the author in the construction of the WKT for derived
from projected CRSes and the calculation of parameters is done with a
script that I had written when I began to need to carry out this type of
transformation. It only requires numpy and is very efficient at finding
transformation parameters. The algorithm on which it is based is not mine.

You can use the script if you consider it convenient, I published it with a
MIT license at https://github.com/gabriel-de-luca/simil.

Regards,
Gabriel De Luca

El jue, 26 ene 2023 a la(s) 14:08, Greg Troxel via QGIS-User (
qgis-user at lists.osgeo.org) escribió:

> Great place to ask IMHO.
>
> These is a combination of a suggestion and a fish for an answer that
> tells me no work is needed.  I don't know how widespread the audience is
> relative to your standards.
>
> 1)
>
> Consider someone with a local coordinate system establish with a total
> station or similar classical methods.  No assumptions on orientation of
> axes, except up is up.  Let's assume there are perhaps hundreds of
> points.  Perhaps this is just a data collector dump and perhaps it is
> gama output.
>
> Further assume the person has absolute positions (lat/lon/HAE) probably
> via GPS RTK, and perhaps standard deviations.
>
> I want to be able to enter the correspondence, and compute a
> transformation that can be not only used in qgis but stored in a file to
> be used with proj/gdal.  And, I want to store the corresponding points
> so that I can re-open, change some, and add some, without starting over.
>
> There is a geoscience plugin that mostly does this but it seemed awkward
> for reasons I don't remember this minute.
>
>
> 2)
>
> Similar, but assume someone has a survey plan with angles and distances,
> and somehow (in a new plugin or separate) converts them to a local
> system (because one can ~never assume the angles are true to any
> particular geodetic coordinate system).  Given 1, this is about entering
> the angles/distances and turning it into a layer, I think.
>
> There is a cadastral plugin but it seems to be about taking a shape and
> producing documents, vs taking documents and producing a shape.
>
>
> 3)
>
> With RTK, one can take 30s, 60s, whatever position traces on a mark.
> Then one can average those.  Multiple such observations over multiple
> days can then be combined to form an estimate for the mark.  There are
> interesting questions here about finding the mark by being close, vs
> labeling, and not labeling is a faster workflow.   I'm doing this
> manually but it would be cool to be more automated.
>
>
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