Re: [Qgis-user] Data volume wms-layer

[Patrick Dunford]

I haven't been able to find out much about the render caching feature. I 
am now running all my computer with the render caching turned off, so 
that less memory and swap resources are consumed in the computer. It 
might be intended with this feature to reduce the time delay for 
downloading tiles from a remote server for people that are using server 
based resources but would also have the (in your case) less desirable 
consequence of consuming significant amounts of data.


On 20/03/19 8:22 PM, Pascale Hutter wrote:

Hi Patrick

Thanks for you reply! It already helps me a lot, as it confirm my 
impression of the new GIS caching far more data in the memory. I was 
unsure whether this was really the case, as I found nothing on the 
Internet about it. However, if you made the same experience this means 
that there is something different in the way it handles raster data.


 I will check, if I can change something in the settings for 
rendering, to solve the problem. If I do find something, I will let 
you know. Would be really great if the data volume could be decreased 
this way. Otherwise I can see no way how I can use QGIS 3.x for small 
environmental projects, which would be a pity.


Thank you for your help!

Pascale

M. Sc. Biologie
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Austrasse 2a | CH-4153 Reinach
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Telefon 061 717 88 87 | Fax 061 717 88 89
hut...@hintermannweber.ch  | 
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Am 19.03.2019 um 15:15 schrieb Patrick Dunford 
mailto:enzedrailm...@gmail.com>>:


I left this question for a few days because I hoped someone with more 
technical knowledge than me of how Qgis works with this type of data 
would be able to answer your question. As a user I don't have the 
same technical insight as one of the developers who may be reading 
this question and more familiar with data processing in the software.


I currently work with projects that use large numbers of data layers 
of raster type, however in my case they are all in files that I have 
downloaded to my computer and loading locally, rather than any type 
of data that could be accessed from an online server.


I have found in experience with working with raster layers that Qgis 
3 is handling them quite differently from previous versions (I have 
been using Qgis since 1.8). It was not until version 2.14 that I 
started working with the projects using these large numbers of raster 
images, and have been using them through 2.14, 2.16 and 2.18 and now 
in releases of version 3.


The map projects I am working on cover a part of New Zealand 
specifically a corridor around 6000 kilometres long and about 20 
metres wide which is covered by geojpeg rasters varying from 0.4 to 
0.1 metre per pixel resolution and the size of each raster is 
generally 4800x7200 pixels.


The experience I had is that Qgis 3.x appears to be caching a lot 
more raster data in memory than I saw with 2.x and it seems to be 
caching every raster in my project, not just the ones that I am 
displaying at the moment. It uses up the resources in my system a lot 
faster than 2.x ever did. And if I use larger size raster files, I 
have seen it run out of resources on the system more than once.


So in terms of the way it consumes resources for rasters, my 
experience is more related to the way I see it using up the physical 
resources on my computer like the physical or virtual memory. I ended 
up adding more RAM to my system and more swap disk space to help deal 
with the extra drain on resources that has happened since upgrading 
to version 3.


There is a section in the settings dialog that specifically relates 
to rendering. I'm not completely confident this is the type of 
situation that would be relevant to your scenario. It may affect my 
situation more if I spent some time playing with these settings 
(render caching for example) but it might not be so relevant to you, 
unless the render caching is causing the software to download a lot 
of raster data from your WMS server. You could try experimenting with 
some of those settings.


On 20/03/19 2:08 AM, Pascale Hutter wrote:

Hi Patrick

Thanks for your interest! Its raster data of aerial images 
(https://shop.swisstopo.admin.ch/de/products/geoservice/swisstopo_geoservices/swisstopoWMS). 
I often use this for small environmental projects of mine, where I 
have no budget to buy any additional data. So far the 5’000 
Megapixel were enough to work during the whole year. Now it was 
finished up within a month, although I did much less work.
I did read, that the whole wms-layer part was newly written for the 
QGIS version 3.x, so maybe this has so

Re: [Qgis-user] problem with new version 3.6.0 Noosa: LOST PAST PROJECTS

[Antongeo76]

Elena Paulon wrote
> I've just downloaded and installed new version 3.6.0 Noosa. Past version
> was madeira 3.4.? Madeira. I use windows 10.
> Since I've installed the new version I have lost ALL MY PAST PROJECT
> FILES.
> I can't find them anymore in the folders of my works.
> Please, how can I have them back? Why has it happened?
> 
> Elena
> 
> 
> *Dott. Forestale Elena Paulon*
> *Contatti:*
> Pec: 

> e.paulon@.conafpec

> Cell: 338 374 49 93
> 
> *PIVA*
> 04015300249
> 
> ___
> Qgis-user mailing list

> Qgis-user@.osgeo

> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user

Hi Elena,
I do the QGIS update at least every 2 days and I never lost data or projects
...
did you save the projects in the QGIS installation directory?
if yes, in this case there is little to do, otherwise you can search through
the file manager * .qgs files or * .qgz files in your pc

Regards

Antonio



-
Antonio
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Re: [Qgis-user] Coordinates from wgs84 utm /expressed in meter) to wgs84 (expressed in degrees)

[Azzurra Lentini]

Hi Bernd,
yes thank you, in fact I meant that transformation.
Thank you a lot for the explaination and for the correction.

Have a nice day,
Azzurra

Bernd Vogelgesang  a écrit :


Hi,

I was at first quite confused by your question.

I don't know of any projection named WGS84-UTM, but i guess you mean
SOME WGS 84 / UTM  projection. I think it's always best to "talk" in
EPSG codes, cause there are so many confusing terms around.

So, assuming you have e.g a point layer in EPSG 32632 (metric) and want
the coordinates calculated in the field calculator, but the result
should be in EPSG 4326 (degree), you can do:

for a new X column

|X( transform( $geometry, 'EPSG:32632', 'EPSG:4326')) |

and similar for a new Y column

|Y( transform( $geometry, 'EPSG:32632', 'EPSG:4326')) |

|in the field calculator.|


||
Answer found here:
https://gis.stackexchange.com/a/242259/8202

Cheers,

Bernd


Am 19.03.19 um 18:43 schrieb Azzurra Lentini:

Good morning,
if for example my project is in this referencing system: WGS84-UTM,
when I ask to calculate the coordinates Y and X (with field calculator
- geometry), it will produce the coordinates in meters.
But what can I do if I want the same coordinates in degrees?
(obviously in the same datum wgs84)

Thank you, Azzurra




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[Qgis-user] problem with new version 3.6.0 Noosa: LOST PAST PROJECTS

[Elena Paulon]

I've just downloaded and installed new version 3.6.0 Noosa. Past version
was madeira 3.4.? Madeira. I use windows 10.
Since I've installed the new version I have lost ALL MY PAST PROJECT FILES.
I can't find them anymore in the folders of my works.
Please, how can I have them back? Why has it happened?

Elena


*Dott. Forestale Elena Paulon*
*Contatti:*
Pec: e.pau...@epap.conafpec.it
Cell: 338 374 49 93

*PIVA*
04015300249
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[Qgis-user] add unique constraint to geopackage in QGIS DB Manager

[Janneke van Dijk]

Dear list,

I would like to make an existing field in a geopackage layer unique - it 
does not contain any data at the moment. In the DB Manager (both QGIS 
2.18 and 3.4 on Windows 10) I have tried many variations of the below:


ALTER TABLE 'RUJWASCO_follow_up' ADD CONSTRAINT 'result_account_uq' 
UNIQUE('result_account');


I have written it without quotes, with double quotes, some with some 
without single and double quotes. I have written it with a space between 
UNIQUE and the bracket. First question is: is it possible to add a 
unique constraint to a geopackage layer? If yes, my second question is - 
what would be the correct syntax? (And maybe: where can I find 
documentation about geopackage sql syntax?).


Thanks for any insights...

Janneke


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