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Rapporto di allungamento

Introduzione

Calcolare il rapporto di allungamento (di Whitebox) usando le espressioni di QGIS.

!!! Abstract "Elongation ratio" Il rapporto di allungamento (E) è:

E = 1 - S / L Dove S è la lunghezza dell'asse corto e L è la lunghezza dell'asse lungo. Le lunghezze degli assi vengono determinate stimando il riquadro di delimitazione minimo. 

The launch of QField 3.0 was a big deal, but now we’re back to focusing on smaller, more frequent updates. Don’t let the shorter change log for 3.1 trick you – there are lots of cool new features in this update!

Main highlights

One of the main improvements in this release is the brand-new functionality to enable snapping to common angles while digitizing. When enabled, the coordinate cursor will snap to configured angles alongside a visual guideline. This comes in handy when adding new geometries while surveying features with regular angles (e.g. buildings, parking lots, etc.). As QField gets more digitizing functionalities, we’ve taken the time to implement a nifty UI that collapses digitizing toggle buttons into a drawer, leaving extra space for the map canvas to shine through.

In addition, the vertex editor - one of QField’s most advanced geometry tools - received tons of love during this development cycle, focusing on improving its usability. Changes worth mentioning include:

• A new undo button allows users to revert individual vertex manipulations in case of mistaken adjustment, which can save you from having to cancel a large set of ongoing manipulations;
• The possibility to select vertices using finger tapping on the screen, dramatically improving the user experience;
• Clearer on-screen markers to represent vertices and
• Tons of bug fixes to the vertex editor itself, as well as the broader set of geometry tools.

It is now possible to lock the geometry of individual features within a single vector layer. While QField has long supported the concept of a locked geometry state for vector layers, that was until now a layer-wide toggle. With the new version of QField, a data-defined property can dictate whether a given feature geometry can be edited. Interested in geofenced geometry editing? We’ve got you covered ;) This functionality requires the latest version of QFieldSync, which is available through QGIS’ plugin manager.

Noticeably improvements

Permission handling has been improved across all platforms. On Android, QField now delays the permission request for camera, microphone, location, and Bluetooth access until needed. This makes for a much friendlier user experience.

QField 3.0 was one of the largest releases, with major changes in its underlying libraries, including a migration to Qt 6. With the community’s help, we have spent countless hours testing before release. However, it is never a bulletproof process, and that version came with a few noticeable regressions. In particular, camera handling on Android suffered from upstream issues with Qt. We’ve tracked as many of those as possible, making this new version much more stable. One lingering camera issue remains and will be fixed upstream in the next three weeks; we’ll update as soon as it is available.

Finally, long-time users of QField will notice improvements in how geometry highlights and digitizing rubber bands are drawn. We’ve doubled down on efforts to ensure that the digitized geometries and the coordinate cursor itself are always clearly visible, whether overlaid against the canvas’s light or dark parts.

We want to extend a heartfelt thank you to our sponsors for their generous support. If you’re inspired by the developments in QField and want to contribute, please consider donating . Your support will help us continue to innovate and improve this tool for everyone’s benefit.

Crea date da una successione numerica

Introduzione

Data una data iniziale e una serie di numeri da 0 a 999, popolare un attributo data che segue il seguente pattern: a 0 corrisponde la data 01/01/2019, a 1 corrisponde la data 02/01/2019 e così via fino a 999, ovvero 26/09/2021.

!!! Abstract "make_date & make_interval" Queste due funzioni permettono di risolvere il quesito esposto sopra, vediamo come

Un uso intelligente della distanza di LEVENSHTEIN

Introduzione

"Quando i maledetti "pubblicatori" di dati, scrivono i nomi delle Regioni errati e/o senza codici regionali, il valore minimo della distanza Levenshtein può essere una salvezza" (cit. Andrea Borruso)

!!! Abstract "LEVENSHTEIN" Restituisce la distanza di Levenshtein tra due stringhe. Questa equivale al minimo numero di modifiche di carattere (inserimenti, cancellazioni o sostituzione) richieste per cambiare una stringa in un'altra. La distanza di Levenshtein è una misura della similarità tra due stringhe. Distanze più piccole corrispondono a stringhe più simili, e distanze più grandi corrispondono a stringhe più differenti. La distanza è sensibile alle lettere maiuscole.

We are very happy and enthusiasts at Oslandia to forward the QField 3.0 release announcement, the new major update of this mobile GIS application based on QGIS.

Oslandia is a strategic partner of OPENGIS.ch, the company at the heart of QField development, as well as the QFieldCloud associated SaaS offering. We join OPENGIS.ch to announce all the new features of QField 3.0.

Get QField 3.0 now !

Shipped with many new features and built with the latest generation of Qt’s cross-platform framework, this new chapter marks an important milestone for the most powerful open-source field GIS solution.

Main highlights

Upon launching this new version of QField, users will be greeted by a revamped recent projects list featuring shiny map canvas thumbnails. While this is one of the most obvious UI improvements, countless interface tweaks and harmonization have occurred. From the refreshed dark theme to the further polishing of countless widgets, QField has never looked and felt better.

The top search bar has a new functionality that allows users to look for features within the currently active vector layer by matching any of its attributes against a given search term. Users can also refine their searches by specifying a specific attribute. The new functionality can be triggered by typing the ‘f’ prefix in the search bar followed by a string or number to retrieve a list of matching features. When expanding it, a new list of functionalities appears to help users discover all of the tools available within the search bar.

QField’s tracking has also received some love. A new erroneous distance safeguard setting has been added, which, when enabled, will dictate the tracker not to add a new vertex if the distance between it and the previously added vertex is greater than a user-specified value. This aims at preventing “spikes” of poor position readings during a tracking session. QField is now also capable of resuming a tracking session after being stopped. When resuming, tracking will reuse the last feature used when first starting, allowing sessions interrupted by battery loss or momentary pause to be continued on a single line or polygon geometry.

On the feature form front, QField has gained support for feature form text widgets, a new read-only type introduced in QGIS 3.30, which allows users to create expression-based text labels within complex feature form configurations. In addition, relationship-related form widgets now allow for zooming to children/parent features within the form itself.

To enhance digitizing work in the field, QField now makes it possible to turn snapping on and off through a new snapping button on top of the map canvas when in digitizing mode. When a project has enabled advanced snapping, the dashboard’s legend item now showcases snapping badges, allowing users to toggle snapping for individual vector layers.

In addition, digitizing lines and polygons by using the volume up/down hardware keys on devices such as smartphones is now possible. This can come in handy when digitizing data in harsh conditions where gloves can make it harder to use a touch screen.

While we had to play favorites in describing some of the new functionalities in QField, we’ve barely touched the surface of this feature-packed release. Other major additions include support for Near-Field Communication (NFC) text tag reading and a new geometry editor’s eraser tool to delete part of lines and polygons as you would with a pencil sketch using an eraser.

Thanks to Deutsches Archäologisches Institut, Groupements forestiers Québec, Amsa, and Kanton Luzern for sponsoring these enhancements.

Quality of life improvements

Starting with this new version, the scale bar overlay will now respect projects’ distance measurement units, allowing for scale bars in imperial and nautical units.

QField now offers a rendering quality setting which, at the cost of a slightly reduced visual quality, results in faster rendering speeds and lower memory usage. This can be a lifesaver for older devices having difficulty handling large projects and helps save battery life.

Vector tile layer support has been improved with the automated download of missing fonts and the possibility of toggling label visibility. This pair of changes makes this resolution-independent layer type much more appealing.

On iOS, layouts are now printed by QField as PDF documents instead of images. While this was the case for other platforms, it only became possible on iOS recently after work done by one of our ninjas in QGIS itself.

Many thanks to DB Fahrwgdienste for sponsoring stabilization efforts and fixes during this development cycle.

Qt 6, the latest generation of the cross-platform framework powering QField

Last but not least, QField 3.0 is now built against Qt 6. This is a significant technological milestone for the project as this means we can fully leverage the latest technological innovations into this cross-platform framework that has been powering QField since day one.

On top of the new possibilities, QField benefited from years of fixes and improvements, including better integration with Android and iOS platforms. In addition, the positioning framework in Qt 6 has been improved with awareness of the newer GNSS constellations that have emerged over the last decade.

Forest-themed release names

Forests are critical in climate regulation, biodiversity preservation, and economic sustainability. Beginning with QField 3.0 “Amazonia” and throughout the 3.X’s life cycle, we will choose forest names to underscore the importance of and advocate for global forest conservation.

Software with service

OPENGIS.ch and Oslandia provides the full range of services around QField and QGIS : training, consulting, adaptation, specific development and core development, maintenance and assistance. Do not hesitate to contact us and detail your needs, we will be happy to collaborate : [email protected]

As always, we hope you enjoy this new release. Happy field mapping!

Help in linea

Introduzione

L'help in linea del motore di espressioni di QGIS è utile e va consultato sempre. In questo post vediamo alcuni aspetti importanti.

!!! Abstract "Help in linea Field Calc" L'help in linea del Field calc è indispensabile per un uso corretto delle espressioni, contiene la definizione della funzione/espressione, la sintassi, spiegazione degli argomenti ed esempi

Le variabili in QGIS

Introduzione

Le variabili sono una nuova funzionalità introdotta in QGIS 2.12 Lyon (2015) che consente di creare valori preimpostati da utilizzare ovunque sia possibile utilizzare un'espressione.

!!! Abstract "Variabili" Rappresentano un nuovo concetto che dà la possibilità di impostare variabili personalizzate da utilizzare nel motore delle espressioni di QGIS