Impostazioni di progetto influenzano alcune funzioni

Introduzione

Alcune funzioni di QGIS dipendono dalle impostazioni di progetto, questo significa che le stesse funzioni in progetti diversi possono restituire valori diversi. In questo post vedremo le principali funzioni di QGIS da attenzionare.

!!! Abstract "esempio" $area <> area(@geometry)

Come cercare un valore in funzione di un altro

Introduzione

Alcune volte nasce l'esigenza di cercare un valore in una tabella in funzione di un altro valore presente nella stessa tabella, un po' come fa la funzione cerca verticale di Excel, e utilizzarlo in un altro layer.

!!! Abstract "Funzione" La funzione che permette di fare questa magia è la funzione get_feature

HfcQGIS e la sezione Blog

Introduzione

Benvenuti nel nuovo blog di HfcQGIS!

HfcQGIS è la guida al calcolatore di campi di QGIS per la condivisione di conoscenze ed ora ha il suo Blog!!!.

HfcQGIS è un sito web nato nel 2018 da un'idea di Totò Fiandaca e realizzato con la comunità OpenDataSicilia, un particolare grazie va a Giovan Battista Vitrano che mantiene sempre aggiornato il tema del sito alle ultime novità. L'obiettivo iniziale del sito era quello di fornire una guida completa al calcolatore di campi, un potente strumento che consente di eseguire calcoli sui dati geografici.

Negli anni, HfcQGIS si è evoluto in una piattaforma di condivisione di contenuti per la comunità QGIS. Il sito offre ora una serie di risorse, tra cui:

QField is a community-driven open-source project. It is free to share, use and modify and it will stay like that. The very essence of a community is to help and support each other. And that’s where YOU come into play. To make it work we need your support!

For those who don’t know much about the concept of open source projects, a bit of background. Investing in open-source projects is a technical and ethical decision for OPENGIS.ch. Open source is a technological advantage, as we receive input from many developers worldwide who are motivated to work out the best possible software. It prevents our customers from vendor lock-in and allows complete ownership and control of the developed software. And finally, not only financially independent businesses and people should benefit from professional software but also those who might not have the financial means to pay for features, and licences.

You are not a developer, but you still like to use QField and support it? Good news. You don’t have to be a developer to use, contribute or recommend the app. There are plenty of things that need to be done to help QField to remain the powerful software it is right now and become even better. Here are a few suggestions on how you can give something back.

1. Review the app ★★★★★ in google’s play store or apple’s app store .
2. Let the world know about it! It doesn’t matter if you’re on Twitter, LinkedIn, Instagram or any other social media platform. Show and tell about where QField helped you. We appreciate every post and we promise to like, share and comment.
3. Write about your experience and please let us know. Be it in your blog or as a new success story. Insights into field projects are extremely valuable. It helps us to make the app even more efficient for your work, and it helps others to understand the range of applications for QField.
4. Register for a paid QFieldCloud account . QFieldCloud allows to synchronize and merge the data collected in QField. QFieldCloud is hosted by the makers of QField and by getting an account you help QField too.

Do you want to do something that is more hands-on and directly linked to the app? No problem.

1. Help with the documentation . You can document features, or improve the documentation in English. Read the how-to guide to get started.
2. And if you are multilingual you might consider translating the documentation or the app in your language .
3. Become a beta tester and be the first to report a bug! When something doesn’t work properly it might be a bug. The quicker we know about it, the faster it can be resolved.
4. You can ask and answer questions on gis.stackexchange and help others on the user discussions platform .
5. If you are a developer and you want to get involved in QField development, please refer to the individual documentation for QField , QFieldCloud and QFieldSync .

And now finally for those of you who have the financial means, you can either sponsor a feature or subscribe to one of the monthly sponsorships . By doing so you help get freshly baked QField versions straight to everyone’s devices.

Nothing in it for you? In that case, just drop by to say thank you or have a hot or cold beverage with us next time you meet OPENGIS.ch at a conference and you might make our day!
Want to know more about the idea of community-driven open-source projects and the QGIS project in particular? Check out Nyall Dawson’s blog post about how to effectively get things done in open source !

The international community of QGIS contributors got together in person from 18 to 22 August in parallel to OpenStreetMap State of The Map event and right before the FOSS4G . So there was a lot of open source geo power concentrated in the beautiful city of Florence in those days. It was my first participation and all I knew was that it’s supposed to be an unconference. This means, there is no strict schedule but space and opportunity for everyone to present their work or team up to discuss and hack on specific tasks to bring the QGIS project to the next level.

Introduction and first discussions

We were a group of six OPENGIS.ch members arriving mostly on Thursday, spending the day shopping and moving into our city apartment. In the evening we went to a Bisteccheria to eat the famous Fiorentina steak. It was big and delicious as was the food in general. Though, I am eating vegetarian since to compensate. On Friday we went to the Campus to meet the other contributors. After a warm welcome by the organizer, Rossella and our CEO and QGIS chair Marco Bernasocchi we did an introduction round where everyone mentioned their first QGIS version ever used. At this point, I became aware of the knowledge and experience I was sharing the room with. Besides this, I noticed that there was another company attending with several members, namely Tim Sutton’s Kartoza, which is also contributing a lot to QGIS. The first discussion was about QGIS funding model, vision, communication and on the new website in planning. This discussion then moved into some smaller groups including most of the long term contributors. I was looking around, physically and virtually, and tried to process all the new inputs and to better understand the whole QGIS world. Besides, I noticed my colleague Ivan having problems with compiling QGIS after upgrading to Ubuntu 22.04 which then motivated my other colleague Clemens to implement a docker container to do the compilation. Nevertheless, I postponed my Ubuntu upgrade. That evening we went out all together to have a beer or two and play some pool sessions and table football. Finally, the OPENGIS.ch crew navigated back home pairing a high-precision GNSS sensor with a mobile device running OpenStreetMap in QField . We arrived back home safely and super precise.

First tasks and coffee breaks

There was catering in the main hall covering breakfast, lunch and coffee breaks. It never took long after grabbing a cup of coffee to find yourself in a conversation with either fellow contributors or OpenStreetMap folks. I chatted with a mapper from Japan about mobile apps, an engineer from Colombia about travelling and a freelancer from the Netherlands about GDAL, to name 3 coffees out of many.

QGIS plugins website

After some coffee, Matthias Kuhn, our CTO and high-ranking QGIS contributor, asked me whether I could improve some ugly parts of QGIS plugins website . So I had my first task which I started working on immediately. The task was to make the site more useful on mobile devices which would be achieved by collapsing some unimportant information and even removing other parts. I noticed some quirks in the development workflow, so I also added some pre-commit hooks to the dev setup. Dimas Ciputra from Kartoza helped me finalize the improvements and merge them into master branch on github .

QGIS website downloads section

Regis Haubourg asked to help simplify the QGIS Downloads for Windows section on the main QGIS website. We played around in the browser dev tools until we thought the section looked about right. I then checked out the github repo and started implementing the changes. I need to say the tech stack is not quite easy to develop with currently, but there is a complete rework in planning. Anyway, following the pull request on github a lively discussion started which is ongoing by the time of writing. And this is a good thing and shows how much thought goes into this project.

Presentations

There were many interesting and sometimes spontaneous presentations which always involved lively discussions. Amy Burness from Kartoza presented new styling capabilities for QGIS, Tobias Schmetzer from the Bavarian Center for Applied Energy Research presented the geo data processing and pointed out issues he encountered using QGIS on this and Etienne Trimaille from 3liz talked about qgis-plugins-ci , just to name a few.

Amazing community

On Saturday evening a bus showed up at the campus and took us on a trip up to the hills. After quite a long ride we arrived at a restaurant high up with mind-blowing view of the city. I forgot how many rounds of Tuscan food were served, but it was delicious throughout. An amazing evening with fruitful conversations and many laughs.

The weather was nice and hot, the beers cold, the Tuscan food delicious and the contributors were not only popular Github avatars but really nice people. Thank you QGIS.

Starting with QField 2.2, users can fully rely on animation capabilities that have made their way into QGIS during its last development cycle. This can be a powerful mean to highlight key elements on a map that require special user attention.

The example below demonstrates a scenario where animated raster markers are used to highlight active fires within the visible map extent. Notice how the subtle fire animation helps draw viewers’ eyes to those important markers.

Animated raster markers is a new symbol layer type in QGIS 3.26 that was developed by Nyall Dawson . Supported image formats include GIF, WEBP, and APNG.

The second example below showcases more advanced animated symbology which relies on expressions to animate several symbol properties such as marker size, border width, and color opacity. While more complex than simply adding a GIF marker, the results achieved with data-defined properties animation can be very appealing and integrate perfectly with any type of project.

https://player.vimeo.com/video/732691644

You’ll quickly notice how smooth the animation runs. That is thanks to OPENGIS.ch’s own ninjas having spent time improving the map canvas element’s handling of layers constantly refreshing. This includes automatic skipping of frames on older devices so the app remains responsive.

Oh, we couldn’t help ourselves but take the opportunity to demonstrate how nice the QField feature form layout is these days in the video above ? To know more about other new features in QField 2.2, go and read the release page .

Happy field mapping to all!

The lovely animal markers used in the zoo example above were made by Serbian artist Arsenije Vujovic .

What are we looking for?

We would like to use WMS offline on QField. For that, we need to figure out what is the best way to get a raster from a WMS and which format is the most efficient (size and performance).

In this post we’ll show you is how to generate the ideal raster file from a WMS and the results of our efficiency tests for the the different raster formats.

WMS to GPKG

The simple way

If there is no limitation on the WMS or you need only a small region, here is the easiest process.

1. Request the WMS and store a description file in XML :

gdal_translate "WMS:url" file.xml -of WMS

1. Create a Geopackage from the information in the description file.

gdal_translate -of GPKG file.xml file.gpkg -co TILE_FORMAT=JPEG

That was quite simple, right?

The larger datasets way

If the command takes too much time, it means that it is trying to download too much data and could be caused by downloading higher resolution data than required.
The command might even completely fail if it contains a request for bigger data blocks thant the server allows.

Here is the process to get larger datasets in a simple way. Let’s use a real example:

1. Use gdal_translate "WMS:https://www.gebco.net/data_and_products/gebco_web_services/web_map_service/mapserv?request=getmap&service=wms&crs=EPSG:4326&format=image/jpeg&layers=gebco_latest&version=1.1.0" test.xml -of WMS
2. Open the test.xml file for editing, here you’ll find the parameters of the WMS. We change the “SizeX” to 3600 and “SizeY” to 1800. By changing these parameters we lower the resolution. It is important to keep proportionality.
3. Another thing we need to change are “BlockSizeX” and “BlockSizeY” that define the size of the tiles. We change both to 2048.
4. Finally, use gdal_translate -of GPKG test.xml test.gpkg -co TILE_FORMAT=JPEG
5. To make a Geopackage pyramid use gdaladdo GPKG:test.gpkg:gebco_latest. It will replace the Geopackage, if you want to keep the original one, you need to copy it first.

Now you have a raster Geopackage that you can use in QField.

Testing raster formats

Preparing the files

As first step we exported our test orthophoto WMS to a plain GeoTIFF using QGIS’ default behaviour.

Formatgdal_translategdaladdogpkg JPEGgdal_translate -of GPKG “C:\test\ortho_test.tif” “C:\test\test_JPEG.gpkg” -co TILE_FORMAT=JPEG gpkg PNGgdal_translate -of GPKG “C:\test\ortho_test.tif” “C:\test\test_PNG.gpkg” -co TILE_FORMAT=PNGgpkg PNG_JPEGgdal_translate -of GPKG “C:\test\ortho_test.tif” “C:\test\test_PNG_JPEG.gpkg” -co TILE_FORMAT=PNG_JPEGgpkg PNG8gdal_translate -of GPKG “C:\test\ortho_test.tif” “C:\test\test_PNG8.gpkg” -co TILE_FORMAT=PNG8gpkg WEBPgdal_translate -of GPKG “C:\test\ortho_test.tif” “C:\test\test_WEBP.gpkg” -co TILE_FORMAT=WEBPgpkg pyramid_JPEGgdal_translate -of GPKG “C:\test\ortho_test.tif” “C:\test\test_JPEG.gpkg” -co TILE_FORMAT=JPEGgdaladdo GPKG:C:\test\test_JPEG.gpkg:test_gpkg_JPEG gpkg pyramid_PNGgdal_translate -of GPKG “C:\test\ortho_test.tif” “C:\test\test_PNG.gpkg” -co TILE_FORMAT=PNGgdaladdo GPKG:C:\test\test_PNG.gpkg:test_gpkg_PNGgpkg pyramid_PNG_JPEGgdal_translate -of GPKG “C:\test\ortho_test.tif” “C:\test\test_PNG_JPEG.gpkg” -co TILE_FORMAT=PNG_JPEGgdaladdo GPKG:C:\test\test_PNG_JPEG.gpkg:test_gpkg_PNG_JPEGgpkg pyramid_PNG8gdal_translate -of GPKG “C:\test\ortho_test.tif” “C:\test\test_PNG8.gpkg” -co TILE_FORMAT=PNG8gdaladdo GPKG:C:\test\test_PNG8.gpkg:test_gpkg_PNG8gpkg pyramid_WEBPgdal_translate -of GPKG “C:\test\ortho_test.tif” “C:\test\test_WEBP.gpkg” -co TILE_FORMAT=WEBPgdaladdo GPKG:C:\test\test_WEBP.gpkg:test_gpkg_WEBPJPEG2000gdal_translate -of JP2OpenJPEG “C:\test\ortho_test.tif” “C:\test\test_jpeg_2000.jpg"COG DEFLATEgdal_translate “C:\test\ortho_test.tif” “C:\test\test_cog.tif” -co TILED=YES -co COPY_SRC_OVERVIEWS=YES -co COMPRESS=DEFLATECOG_JPEGgdal_translate “C:\test\ortho_test.tif” “C:\test\test_cog_JPEG.tif” -co TILED=YES -co COPY_SRC_OVERVIEWS=YES -co COMPRESS=JPEGtifIn QGIS right click on the layer > export > save as > (see the details in the picture under the table)MBTgdal_translate -of MBTILES “C:\test\ortho_test.tif” “C:\test\test_mbt.mbtiles"Creation commands for all the tested formats

Rendering test results

We have tested many formats, here is a table with the results of the size and rendering speed in QGIS and QField.
To analyze the speed we used qgis_bench.exe -i 10 -p "C:\test\test.qgs" >> "C:\test\test.log.
Qgis_bench is a tool that renders a QGIS project a number of times to get performance measurements. The parameter -i is to define the iterations and -p is the project used which contains only the generated raster.

FormatExtent [m]File size [GB]Total_avgTotal_maxdevTotal_minTotal_stdevgpkg JPEG52'880/29'2300.4250.242255.7815.539244.984gpkg PNG52'880/29'2302.9412.002490.328152.142259.859gpkg PNG_JPEG52'880/29'2300.4250.125256.8756.750245.172gpkg PNG852'880/29'2301.4283.875296.40612.625271.250gpkg WEBP52'880/29'2300.3330.238348.10973.534256.703gpkg pyramid_JPEG52'880/29'2300.51.0093.4062.3970.688gpkg pyramid_PNG52'880/29'2303.01.2083.2812.0730.688gpkg pyramid_PNG_JPEG52'880/29'2300.61.4914.3442.8531.016gpkg pyramid_PNG852'880/29'2301.61.5084.3752.8670.969gpkg pyramid_WEBP52'880/29'2300.41.3334.9063.5730.766JPEG200052'880/29'2301.113.888136.109122.2220.219COG DEFLATE52'880/29'2303.6264.427273.09425.411239.016COG_JPEG52'880/29'2301.014.778131.172116.3941.734tif52'880/29'2306.42.3676.7344.3671.672MBT52'880/29'2304.40.4694.6414.1710Comparison of file size and rendering speed of different raster formats. “Total” columns are rendering times in [s]. Lower file size is more storage friendly, lower Total_avg is more performant.

Analysis

File size

The Geopackage WEBP (with and without pyramid) has the best result for file size, but it is not _yet_supported by QField (from 1.6) and is only slightly smaller than the JPEG variant.

Plain GeoTiff, MBTiles, Cloud Optimized GeoTIFF (COG - DEFLATE mode) and Geopackages with PNG generate by far the largest file sizes (up to 20x larger) and are thus not recommended.

Rendering speed

MBTiles are on average double as fast as JPEG Geopackages with pyramids which in turn are more than double as fast as GeoTIFF and 15x faster than COG.
Geopackages without pyramids are 200 to 400 times slower.

Conclusion

Even though MBTiles render faster than the Geopackage pyramid JPEG, they come with an almost 10x bigger storage requirement which makes us say that the best offline raster format supported by QField is Geopackage pyramid JPEG or if you need transparency and slightly smaller files Geopackage pyramid WebP.

If you need transparency before QField 1.6, the best results are achieved with Geopackage pyramid PNG_JPEG.

What a year’s start! After a very packed December publishing all the QGIS on the road videos and quietly releasing QField 1.3 - Ben Nevis we could have gone and relaxed over the holidays. But since we love QField so much we immediately started working on the next iteration. Now, after an intensive testing period, we are proud to announce the release of QField 1.4 - Olavtoppen.

Olavtoppen!? yes, the highest point of Bouvet Island, the remotest island on Earth. And sure enough, QField would follow you there!

As usual, get it on play store or download it from GitHub.

QField Crowdfunding Campaign

Before digging into all the new goodness that you will find in QField 1.4, let’s get a big “Thanks” out to everybody who supported our crowdfunding campaign for improved camera support and all our customers that agreed to open source the work we did for them.

If you like QField, want a new feature or would like to support the project, don’t hesitate to get in touch with us.

Usability enhancements

In QField 1.2 we started to improve on the usability of the user interface. We are constantly working on this with a usability expert to get the user interface to be even more appealing and user-friendly.

Besides lots of clean-up and polishing, QField received two major improvements, a portrait mode and a new welcome screen with recent projects.

Welcome screen with recent projects

QField is all about efficiency. While favourites folders in the file selector already give a great productivity boost, very often we work with the same 3-4 projects. This is why we redesigned the welcome screen to list the last five project used. And if you look carefully you might get a hint of what will be coming soon…

Portrait mode

QField now flawlessly works in portrait mode. We heard you say you needed a comfortable way to work in portrait mode, especially on smartphones. QField forms and button placements are now optimized to be easy to use with your thumbs.

New features

We keep on listening to your feedback and prioritize new features based on it. We did implement some minor features like allowing hiding legend nodes and printing to PDF using the current extent. But this time’s superstars are three highly expected features: Splitting of geometries, compass integration and, yes you guessed right, native camera and gallery app support!

Split Features

A new editing tool is available that allows for splitting existing features. This adds an even more powerful operation to an already impressive geometry editing tools set.

Compass integration

A long-awaited feature! QField now shows you on-screen in which direction you are looking, walking, driving, flying or warping direction. This makes it much easier and more pleasant to navigate in the field.

Native Camera and Gallery

It is now possible to use your favourite camera app so that you have more control over how pictures are taken. It is also possible to select pictures which are already on your device by using the new gallery selector.

Pro Tip: You can use any camera app. For example, you can use the open camera app to create geotagged photos if your preinstalled system camera doesn’t save positioning information in EXIF data.

Pro Tip 2: You can use an image annotation app to add notes, sketches, drawings and so on to your images and then choose them from QField via the add from gallery button.

Antenna Height Correction

For high precision measurements, it’s possible to compensate your altitude by a fixed antenna height. This will then automatically adjust all the digitised altitude values.

JPEG 2000

Support for JPEG 2000 raster datasets was added. This lossy format offers a compression rate at par with proprietary formats like ECW or Mr SID.

Pro Tip: save your base maps in JPEG 2000 to save storage.

New Languages

Thanks to the hard work of our community, QField is now also available in Turkish and Japanese.

New packages

You say: wow that’s a lot! We say: there is more :)
We have upgraded our whole building infrastructure so that you can comfortably get even more QField goodness without having to uninstall your production ready QField.

Automated master builds

After each pull request is merged into our master code, a new package is created and automatically published on the playstore in a dedicated app called QField for QGIS - Unstable (Early Access) . Installing this app will allow you to always have the latest build of QField for testing and giving feedback. On your device, this app is completely separated from the production-ready QField and has a distinctive black icon so that you do not confuse it.

Pull request builds

QField is an extremely active project, and as you see we develop multiple functionalities and fixes at the same time. If you’re particularly interested in one of this, our continuous integration fairy builds and publishes new packages automatically at each commit directly to the pull request you are interested in. To see what we are currently working on, have a look at the pull request overview page .

Experimental Windows builds

Last but definitely not least, we’ve set up an Azure CI infrastructure to build QField for windows. For now, we still consider this experimental but we already had some very successful testing. If you are interested in testing out QField for windows you can get it here , remember it is experimental so don’t use it in production yet and give us as much feedback as possible :)

What’s next?

As you can imagine we’ve had a very busy start of 2020, but even more is to come soon with the next releases of QField. We’d like to thank again all companies and individuals that actively use QField and that invest in making QField even better. If you feel QField misses something you need or would like to support the project, don’t hesitate to get in touch with us.