Re: [Qgis-user] Z and Elevation

2023-06-28 Thread Manolo Terranova via QGIS-User 
Thank you Greg.

EPSG 32632

attached data to this email,

Manolo

On Wed, Jun 28, 2023 at 11:48 PM Greg Troxel  wrote:

> Sebastian Gutwein via QGIS-User  writes:
>
> > Manolo,
> > You may already know this and be asking a deeper question that I am not
> > understanding but in case you are not:
> > The Z is the value derived from the geometry itself that QGIS uses to
> draw
> > the location of the point.
> > The Elevation is an attribute associated with the point (a field in the
> > attribute table).
> > There are many reasons that these might not be the same.
> > It could be that they were derived from two different sources or there
> was
> > a transformation that occurred that changed the Z value.
> > Hope this helps.
> > -Bas
>
> I am a beginner with dealing with height/elevation in qgis, but it seems
> obvious :-) that the Z value is interpreted with respect to the CRS,
> which must necessarily be a lat/lon/vertical.  Some 3D CRSes have
> vertical components that are HAE e.g. EPSG:7912, ITRF2014 lat/lon/hae,
> and some will have vertical components that are some kind of orthometric
> height, e.g. EPSG:5498, NAD83 lat/lon and NAVD88 height.
>
> So "Z should be ellipsoidal" is not in general true.
>
> (Plus, Sebastian's comments sound very useful, and you (Manolo) did not
> post your CRS and data schema.)
>
> Greg
>
<>
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Re: [Qgis-user] Z and Elevation

2023-06-28 Thread Greg Troxel via QGIS-User 
Sebastian Gutwein via QGIS-User  writes:

> Manolo,
> You may already know this and be asking a deeper question that I am not
> understanding but in case you are not:
> The Z is the value derived from the geometry itself that QGIS uses to draw
> the location of the point.
> The Elevation is an attribute associated with the point (a field in the
> attribute table).
> There are many reasons that these might not be the same.
> It could be that they were derived from two different sources or there was
> a transformation that occurred that changed the Z value.
> Hope this helps.
> -Bas

I am a beginner with dealing with height/elevation in qgis, but it seems
obvious :-) that the Z value is interpreted with respect to the CRS,
which must necessarily be a lat/lon/vertical.  Some 3D CRSes have
vertical components that are HAE e.g. EPSG:7912, ITRF2014 lat/lon/hae,
and some will have vertical components that are some kind of orthometric
height, e.g. EPSG:5498, NAD83 lat/lon and NAVD88 height.

So "Z should be ellipsoidal" is not in general true.

(Plus, Sebastian's comments sound very useful, and you (Manolo) did not
post your CRS and data schema.)

Greg
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Re: [Qgis-user] Z and Elevation

2023-06-28 Thread Sebastian Gutwein via QGIS-User 
Manolo,
You may already know this and be asking a deeper question that I am not
understanding but in case you are not:
The Z is the value derived from the geometry itself that QGIS uses to draw
the location of the point.
The Elevation is an attribute associated with the point (a field in the
attribute table).
There are many reasons that these might not be the same.
It could be that they were derived from two different sources or there was
a transformation that occurred that changed the Z value.
Hope this helps.
-Bas

On Wed, Jun 28, 2023 at 1:34 PM Manolo Terranova via QGIS-User <
qgis-user@lists.osgeo.org> wrote:

> Dear all,
> i have a question: if I select a point I get two information about the
> elevation. The Z which should be ellipsoidal, the ELEVATION which resembles
> the geodetic. Why two different informations?
> PDF attached.
> Thank you,
> Manolo
>
>
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-- 
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Regenerative Design Group
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(631) 241-1018

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Re: [Qgis-user] Mesh interpolation technique

2023-06-28 Thread Vincent Cloarec via QGIS-User 
Hi,

Interpolation is done by linear interpolation. With quads, QGIS uses a
triangulation to interpolate values between vertices. There aren't other
interpolation methods for now. But indeed it could be good to add another
interpolation method for quads because the actual interpolation creates
bias.  Note that for rendering, it is possible to change the sample method
to "Neighbor average" that leads to render faces with the average value of
its vertices, but that does not change the value returned by Identify
Results.

For this other question, it is not possible to get the values of the
nearest vertex when extracting values from location in a points layer,
indeed, it could also be a nice feature. Maybe a workaround could be to
extract vertices as a vector layer, then using vector layer algs to do what
you want.

Regards,

Vincent

Le mer. 28 juin 2023 à 12:33, Domenico Micocci via QGIS-User <
qgis-user@lists.osgeo.org> a écrit :

> Dear all,
>
> I've just started working with mesh data in QGIS. In particular, I'm
> working with a regular 2D quad mesh; metadata are as follows:
> Mesh type faces
> Data type vertices
> Is vector No
>
> My QGIS version is 3.22.4
>
> I've noticed that interpolation is performed on faces and that
> interpolated values can be detected through the "Identify Results" Panel.
> However, it is not clear to me which interpolation technique is used and
> whether it is possible to change it or not. Moreover, does the properties
> selected through the Symbology Tab exert any influence on the interpolated
> values or does they only act on the mesh visualization?
>
> Similarly, I suppose that the tool "Export time series values from points
> of a mesh dataset" extracts a timeseries of interpolated values in the
> location(s) specified by a point layer. Is it possible to get the values of
> the nearest vertex of the mesh instead of the interpolated values?
>
> Thank you in advance for your kind support.
> Best regards,
>
> Domenico Micocci
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[Qgis-user] Mesh interpolation technique

2023-06-28 Thread Domenico Micocci via QGIS-User 
Dear all,
I've just started working with mesh data in QGIS. In particular, I'm working 
with a regular 2D quad mesh; metadata are as follows:Mesh type facesData type 
verticesIs vector No
My QGIS version is 3.22.4
I've noticed that interpolation is performed on faces and that interpolated 
values can be detected through the "Identify Results" Panel.However, it is not 
clear to me which interpolation technique is used and whether it is possible to 
change it or not. Moreover, does the properties selected through the Symbology 
Tab exert any influence on the interpolated values or does they only act on the 
mesh visualization?
Similarly, I suppose that the tool "Export time series values from points of a 
mesh dataset" extracts a timeseries of interpolated values in the location(s) 
specified by a point layer. Is it possible to get the values of the nearest 
vertex of the mesh instead of the interpolated values?
Thank you in advance for your kind support.Best regards,
Domenico Micocci___
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Re: [Qgis-user] Reclassify field values from txt rule file in QGIS

2023-06-28 Thread Kirk Schmidt via QGIS-User 

Hi Fabio:


This is GRASS function and you can find an explanation at:

https://www.ibiblio.org/pub/packages/gis/grass/grass63/manuals/html63_user/v.reclass.html

Instead of a simple lookup table, some sql sytax is required.

9110 - (Hainsimsen-Buchenwald)    9110


you would require:


9110

where feature = '9110 - (Hainsimsen-Buchenwald)'or '9110 - 
(Hainsimsen-Buchenwald)(100.0%)' 



Note the single quotations for text.


An easier approach would be top calculate a new field using the field 
calculator and use the string left expression - left(/landclass field/, 4)



Kirk Schmidt

On 6/28/2023 9:52 AM, fabio castelli via QGIS-User wrote:

Dear Qgis users,

I kindly ask for your support with an issue related to the 
reclassification of attribute tables with the v.reclass function.
Here's the link to the question posted on Stackexchenge: 
https://gis.stackexchange.com/questions/462318/reclassify-field-values-from-txt-rule-file-in-qgis


Thank you and best regards,

Fabio Castelli


 
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--
Kirk Schmidt, MScF, BScF, RPF
General Manager
Nortek Resource Solutions Inc.
26 Church Road
Sutherlands River, NS
B0K 1W0
Tel (902) 922.3607
Email:k...@nortekresources.com
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[Qgis-user] Data source manager--Postgresql: how to display schemas comments ?

2023-06-28 Thread celati Laurent via QGIS-User 
Good afternoon,
I work with Postgresql/Postgis server and Qgis desktop as client.
I use several thematic schemas in my postgresql database.
With pgadmin, i fill in the COMMENT section for tables and chemas allowing
to have a short description for each tables and schemas. With Qgis, via the
data source manager, it is possible for tables to get this description.
But i would like to get the schemas's description. By default this does not
seem possible.
I am attaching a screenshot showing that the comments info are correctly
get for the table. But not for the schema level.
[image: image.png]
Thansk a lot.
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[Qgis-user] Reclassify field values from txt rule file in QGIS

2023-06-28 Thread fabio castelli via QGIS-User 
Dear Qgis users,

I kindly ask for your support with an issue related to the reclassification of 
attribute tables with the v.reclass function.
Here's the link to the question posted on Stackexchenge: 
https://gis.stackexchange.com/questions/462318/reclassify-field-values-from-txt-rule-file-in-qgis

Thank you and best regards,

Fabio Castelli


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Re: [QGIS-it-user] INSERIRE TESTO FILE DXF

2023-06-28 Thread Ernesto Sferlazza 
Se parliamo di oggetti tipo testo a riga singola presenti in un file dxf,
gli stessi vengono interpretati, in ambiente GIS, come oggetti di un tema
di punti, ciascuno dei quali è localizzato in corrispondenza del "punto di
inserimento" della rispettiva stringa di testo. Quest'ultima è contenuta
nella tabella, nell'attributo "text". Altri attributi possono contenere
informazioni sull'altezza del testo, sulla rotazione, etc.
Ciò detto, in ambiente GIS la visualizzazione del testo va gestita con gli
strumenti di gestione delle etichette.

Il giorno lun 26 giu 2023 alle ore 12:14 Luca Soccal via QGIS-it-user <
qgis-it-user@lists.osgeo.org> ha scritto:

> Buongiorno, mi potete indicare il procedimento per poter caricare il testo
> di un file dxf in qgis 3.22.14 ?
>
> Grazie
>
>
> L.S.
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[Qgis-user] Idea for an actual 'events' timeline in QGIS

2023-06-28 Thread Richard Duivenvoorde via QGIS-User 

Hi,

I'm involved in a project about mapping bat sensor data over time.
So 'sound' events with timestamp and (approximate) location, in Postgis db.
Some OGC-API features service in front.

Of course this is loaded in QGIS using the Temporal Controller...

But because the data is pretty sparse (over time)... so 'finding' a 'slot' 
filled with data is not so easy: you want to have time steps of an hour, 
looking at data of say a couple of days...

No I was thinking about some visualization of the events on a time line...

Like a time line with tick's or dot's on time positions where there was an 
actual event (on a second canvas?).
The ideal would be that I could click that event and then the location of the 
event(s) would be selected/flashed on the map on the map canvas...

I was thinking to so some second canvas with a slider (like temporal 
controller), but QtSlider is not so easy to adapt (in my experience)...

Or maybe is a combination with Data Plotly?

Anybody build something like that?

Or has ideas for it?

Regards,

Richard Duivenvoorde


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