[Qgis-user] Problems with transformation including height values

[Nyall Dawson]

On Tue, 21 Mar 2023, 8:21 pm Richard McDonnell, <richard.mcdonnell at opw.ie>
wrote:

> Hi,
>
> Just to add to what Nyall said.
>
> See link below, which suggests a way using OGR to carry out the process
> you require.
>
>
>
>
> https://gis.stackexchange.com/questions/324848/transform-datum-csv-csv-using-ogr2ogr
>
>
>
> It suggests you preform your horizontal transformation first, this can be
> done in QGIS, then carry out the Vertical Transformation. This can be done
> in command line, if you are on windows, the best option is to use the *OSGeo4w
> Shell*, as all the needed environmental settings are applied.
>
> I hope the above helps.
>
>
>
> Maybe there is an opportunity to have QGIS preform Vertical translations,
> even if these are a separate step? It’s something that would be useful for
> both Raster and Vector Data.
>

It's definitely on the radar -- especially for transformation of point
clouds. It's just a very involved task with a high degree of complexity,
and will need funding to happen.

Nyall

Regards,
>
>
> Richard
>
>
>
>
>
>
>
> ——
> Richard McDonnell MSc GIS, FME Certified Professional
> *FRM Data Management*
>
> ——
> Oifig na nOibreacha Poiblí
> Office of Public Works
>
> Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36
> Jonathan Swift Street, Trim, Co Meath, C15 NX36
> ——
> M +353 87 688 5964 T +353 46 942 2409
> https://gov.ie/opw
>
> ——
> To send me files larger than 30MB, please use the link below
> https://filetransfer.opw.ie/filedrop/richard.mcdonnell@opw.ie
>
> Email Disclaimer:
> https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/
>
> ——
> MSc GIS, FME Certified Professional
>
> ——
> Oifig na nOibreacha Poiblí
> Office of Public Works
>
> Sráid Jonathan Swift, Baile Átha Troim, Co na Mí, C15 NX36
> Jonathan Swift Street, Trim, Co Meath, C15 NX36
> ——
> M +353 87 688 5964 T +353 46 942 2409
> https://https://gov.ie/opw <https://www.opw.ie>
>
> ——
> Email Disclaimer:
> https://www.gov.ie/en/organisation-information/439daf-email-disclaimer/
> <https://www.opw.ie/en/disclaimer/>
>
> *From:* QGIS-User <qgis-user-bounces at lists.osgeo.org> *On Behalf Of *Nyall
> Dawson via QGIS-User
> *Sent:* 21 March 2023 10:14
> *To:* Bo Victor Thomsen <bo.victor.thomsen at gmail.com>
> *Cc:* qgis-user <qgis-user at lists.osgeo.org>
> *Subject:* Re: [Qgis-user] Problems with transformation including height
> values
>
>
>
>
>
> On Tue, 21 Mar 2023, 8:06 pm Bo Victor Thomsen via QGIS-User, <
> qgis-user at lists.osgeo.org> wrote:
>
> Hi list -
>
> I have a problem with transforming a csv file containing x,y *and *z
> values from EPSG:4326 to EPSG:7416, i.e I want to transform the height
> value from LongLat/ WGS84 ellipsoid height to UTM32/Etrs89 with vertical
> reference DVR90.
>
> The file look like this:
>
>
> *== data.csv, EPSG:4326 id: col1, x: col3, y: col2, z: col4 == *
> a;55.0;12.0;42.0
> b;55.05;12.0;43.0
> c;55.10;12.0;44.0
> d;55.15;12.0;45.0
> e;55.20;12.0;46.0
> *=======================*
>
> *Step 1*: I import the file into QGIS using the Data Source Manager -->
> "Delimited Text" and define the projection to be EPSG:4326 *and* to
> include z values. This works and the points are shown on my map where I
> expect them to be (Somewhere in the middle of Zealand, Denmark)
>
> *Step 2*: I export the layer as a geojson file using "Export" --> "Save
> features as.." from the layer manager and choose EPSG:7416 (UTM32/ETRS89
> with DVR90 as vertical reference. And to include z-values
>
> The resulting file looks like this:
>
>
> *== data.geojson, EPSG:7416 == *{
> "type": "FeatureCollection",
> "name": "data",
> "crs": { "type": "name", "properties": { "name":
> "urn:ogc:def:crs:EPSG::4979" } },
> "features": [
> { "type": "Feature", "properties": { "field_1": "a", "field_2": 55.0,
> "field_3": 12.0, "field_4": 42.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.0, 42.0 ] } },
> { "type": "Feature", "properties": { "field_1": "b", "field_2": 55.05,
> "field_3": 12.0, "field_4": 43.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.05, 43.0 ] } },
> { "type": "Feature", "properties": { "field_1": "c", "field_2": 55.1,
> "field_3": 12.0, "field_4": 44.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.1, 44.0 ] } },
> { "type": "Feature", "properties": { "field_1": "d", "field_2": 55.15,
> "field_3": 12.0, "field_4": 45.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.15, 45.0 ] } },
> { "type": "Feature", "properties": { "field_1": "e", "field_2": 55.2,
> "field_3": 12.0, "field_4": 46.0 }, "geometry": { "type": "Point",
> "coordinates": [ 12.0, 55.2, 46.0 ] } }
> ]
> }
> *=======================*
>
> The new file is shown in my map exactly on top of the original point
> layer, meaning the horizontal projection is accurate. However, my z
> coordinates are not reprojected to the new vertical reference. All the
> z-values are exactly the same as the values in the .csv - file.
>
> After some digging through Google and other places, I discover that
> EPSG:4326 * doesn't* have a z component. Surprise ! You have to use
> EPSG:4979, which is the same as EPSG:4326 with ellipsoid height.
>
> But, *after *repeating *step 1*, *but* using EPSG:4979 as CRS during
> import, and subsequently repeating *step 2*, I get the exact same result:
> No transformation of height values.
>
> So, what is not working ? Am I doing something wrong ?? Or is QGIS
> incapable of transforming z values ???
>
>
>
> The second -- qgis currently doesn't handle vertical crs at all. My
> recommendation is to use gdal utilities to do a transform respecting
> vertical datums.
>
>
>
> Nyall
>
>
>
> --
>
> Med venlig hilsen / Best regards
>
>
>
> Bo Victor Thomsen
>
> _______________________________________________
> QGIS-User mailing list
> QGIS-User at lists.osgeo.org
> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20230321/056c7449/attachment.htm>