Tag: qgis

QGIS Versioning now supports foreign keys!

QGIS-versioning is a QGIS and PostGIS plugin dedicated to data versioning and history management. It supports :

  • Keeping full table history with all modifications
  • Transparent access to current data
  • Versioning tables with branches
  • Work offline
  • Work on a data subset
  • Conflict management with a GUI

QGIS versioning conflict management

In a previous blog article we detailed how QGIS versioning can manage data history, branches, and work offline with PostGIS-stored data and QGIS. We recently added foreign key support to QGIS versioning so you can now historize any complex database schema.

This QGIS plugin is available in the official QGIS plugin repository, and you can fork it on GitHub too !

Foreign key support

TL;DR

When a user decides to historize its PostgreSQL database with QGIS-versioning, the plugin alters the existing database schema and adds new fields in order to track down the different versions of a single table row. Every access to these versioned tables are subsequently made through updatable views in order to automatically fill in the new versioning fields.

Up to now, it was not possible to deal with primary keys and foreign keys : the original tables had to be constraints-free.  This limitation has been lifted thanks to this contribution.

To make it simple, the solution is to remove all constraints from the original database and transform them into a set of SQL check triggers installed on the working copy databases (SQLite or PostgreSQL). As verifications are made on the client side, it’s impossible to propagate invalid modifications on your base server when you “commit” updates.

Behind the curtains

When you choose to historize an existing database, a few fields are added to the existing table. Among these fields, versioning_ididentifies  one specific version of a row. For one existing row, there are several versions of this row, each with a different versioning_id but with the same original primary key field. As a consequence, that field cannot satisfy the unique constraint, so it cannot be a key, therefore no foreign key neither.

We therefore have to drop the primary key and foreign key constraints when historizing the table. Before removing them, constraints definitions are stored in a dedicated table so that these constraints can be checked later.

When the user checks out a specific table on a specific branch, QGIS-versioning uses that constraint table to build constraint checking triggers in the working copy. The way constraints are built depends on the checkout type (you can checkout in a SQLite file, in the master PostgreSQL database or in another PostgreSQL database).

What do we check ?

That’s where the fun begins ! The first thing we have to check is key uniqueness or foreign key referencing an existing key on insert or update. Remember that there are no primary key and foreign key anymore, we dropped them when activating historization. We keep the term for better understanding.

You also have to deal with deleting or updating a referenced row and the different ways of propagating the modification : cascade, set default, set null, or simply failure, as explained in PostgreSQL Foreign keys documentation .

Nevermind all that, this problem has been solved for you and everything is done automatically in QGIS-versioning. Before you ask, yes foreign keys spanning on multiple fields are also supported.

What’s new in QGIS ?

You will get a new message you probably already know about, when you try to make an invalid modification committing your changes to the master database

Error when foreign key constraint is violated

Partial checkout

One existing Qgis-versioning feature is partial checkout. It allows a user to select a subset of data to checkout in its working copy. It avoids downloading gigabytes of data you do not care about. You can, for instance, checkout features within a given spatial extent.

So far, so good. But if you have only a part of your data, you cannot ensure that modifying a data field as primary key will keep uniqueness. In this particular case, QGIS-versioning will trigger errors on commit, pointing out the invalid rows you have to modify so the unique constraint remains valid.

Error when committing non unique key after a partial checkout

Tests

There is a lot to check when you intend to replace the existing constraint system with your own constraint system based on triggers. In order to ensure QGIS-Versioning stability and reliability, we put some special effort on building a test set that cover all use cases and possible exceptions.

What’s next

There is now no known limitations on using QGIS-versioning on any of your database. If you think about a missing feature or just want to know more about QGIS and QGIS-versioning, feel free to contact us at infos+data@oslandia.com. And please have a look at our support offering for QGIS.

Many thanks to eHealth Africa who helped us develop these new features. eHealth Africa is a non-governmental organization based in Nigeria. Their mission is to build stronger health systems through the design and implementation of data-driven solutions.

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(Fr) Oslandia recrute : développeur(se) C++ et Python

Sorry, this entry is only available in French.
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Using QGIS from Conda

QGIS recipes have been available on Conda for a while, but now, that they work for the three main operating systems, getting QGIS from Conda is s starting to become a reliable alternative to other QGIS distributions. Anyway, let’s rewind a bit…

What is Conda?

Conda is an open source package management system and environment management system that runs on Windows, macOS and Linux. Conda quickly installs, runs and updates packages and their dependencies. Conda easily creates, saves, loads and switches between environments on your local computer. It was created for Python programs, but it can package and distribute software for any language.

Why is that of any relevance?

Conda provides a similar way to build, package and install QGIS (or any other software) in Linux, Windows, and Mac.

As a user, it’s the installation part that I enjoy the most. I am a Linux user, and one of the significant limitations is not having an easy way to install more than one version of QGIS on my machine (for example the latest stable version and the Long Term Release). I was able to work around that limitation by compiling QGIS myself, but with Conda, I can install as many versions as I want in a very convenient way.

The following paragraphs explain how to install QGIS using Conda. The instructions and Conda commands should be quite similar for all the operating systems.

Anaconda or miniconda?

First thing you need to do is to install the Conda packaging system. Two distributions install Conda: Anaconda and Miniconda.

TL;DR Anaconda is big (3Gb?) and installs the packaging system and a lot of useful tools, python packages, libraries, etc… . Miniconda is much smaller and installs just the packaging system, which is the bare minimum that you need to work with Conda and will allow you to selectively install the tools and packages you need. I prefer the later.

For more information, check this stack exchange answer on anaconda vs miniconda.

Download anaconda or miniconda installers for your system and follow the instructions to install it.

Windows installer is an executable, you should run it as administrator. The OSX and Linux installers are bash scripts, which means that, once downloaded, you need to run something like this to install:

bash Miniconda3-latest-Linux-x86_64.sh

Installing QGIS

Notice that the Conda tools are used in a command line terminal. Besides, on Windows, you need to use the command prompt that is installed with miniconda.

Using environments

Conda works with environments, which are similar to Python virtual environments but not limited only to python. Basically, it allows isolating different installations or setups without interfering with the rest of the system. I recommend that you always use environments. If, like me, you want to have more that one version of QGIS installed, then the use of environments is mandatory.

Creating an environment is as easy as entering the following command on the terminal:

conda create --name <name_of_the_environment>

For example,

conda create --name qgis_stable

You can choose the version of python to use in your environment by adding the option python=<version>. Currently versions of QGIS run on python 3.6, 3.7, 3.8 and 3.9.

conda create –name qgis_stable python=3.7

To use an environment, you need to activate it.

conda activate qgis_stable

Your terminal prompt will show you the active environment.

(qgis_stable) aneto@oryx:~/miniconda3$

To deactivate the current environment, you run

conda deactivate

Installing packages

Installing packages using Conda is as simples as:

conda install <package_name>

Because conda packages can be stored in different channels, and because the default channels (from the anaconda service) do not contain QGIS, we need to specify the channel we want to get the package from. conda-forge is a community-driven repository of conda recipes and includes updated QGIS packages.

conda install qgis --channel conda-forge

Conda will download the latest available version of QGIS and all its dependencies installing it on the active environment.

Note: Because conda always try to install the latest version, if you want to use the QGIS LTR version, you must specify the QGIS version.

conda install qgis=3.10.12 --channel conda-forge

Uninstalling packages

Uninstalling QGIS is also easy. The quickest option is to delete the entire environment where QGIS was installed. Make sure you deactivate it first.

conda deactivate
conda env remove --name qgis_stable

Another option is to remove QGIS package manually. This is useful if you have other packages installed that you want to keep.

conda activate qgis_stable
conda remove qgis -c conda-forge

This only removes the QGIS package and will leave all other packages that were installed with it. Note that you need to specify the conda-forge channel. Otherwise, Conda will try to update some packages from the default channels during the removal process, and things may get messy.

Running QGIS

To run QGIS, in the terminal, activate the environment (if not activated already) and run the qgis command

conda activate qgis_stable
qgis

Updating QGIS

To update QGIS to the most recent version, you need to run the following command with the respective environment active

conda update qgis -c conda-forge

To update a patch release for the QGIS LTR version you run the install command again with the new version:

conda install qgis=3.10.13 -c conda-forge

Some notes and caveats

Please be aware that QGIS packages on Conda do not provide the same level of user experience as the official Linux, Windows, and Mac installer from the QGIS.org distribution. For example, there are no desktop icons or file association, it does not include GRASS and SAGA, etc …

On the other hand, QGIS installations on Conda it will share user configurations, installed plugins, with any other QGIS installations on your system.

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Thoughts on “FOSS4G/SOTM Oceania 2018”, and the PyQGIS API improvements which it caused

Last week the first official “FOSS4G/SOTM Oceania” conference was held at Melbourne University. This was a fantastic event, and there’s simply no way I can extend sufficient thanks to all the organisers and volunteers who put this event together. They did a brilliant job, and their efforts are even more impressive considering it was the inaugural event!

Upfront — this is not a recap of the conference (I’m sure someone else is working on a much more detailed write up of the event!), just some musings I’ve had following my experiences assisting Nathan Woodrow deliver an introductory Python for QGIS workshop he put together for the conference. In short, we both found that delivering this workshop to a group of PyQGIS newcomers was a great way for us to identify “pain points” in the PyQGIS API and areas where we need to improve. The good news is that as a direct result of the experiences during this workshop the API has been improved and streamlined! Let’s explore how:

Part of Nathan’s workshop (notes are available here) focused on a hands-on example of creating a custom QGIS “Processing” script. I’ve found that preparing workshops is guaranteed to expose a bunch of rare and tricky software bugs, and this was no exception! Unfortunately the workshop was scheduled just before the QGIS 3.4.2 patch release which fixed these bugs, but at least they’re fixed now and we can move on…

The bulk of Nathan’s example algorithm is contained within the following block (where “distance” is the length of line segments we want to chop our features up into):

for input_feature in enumerate(features):
    geom = feature.geometry().constGet()
    if isinstance(geom, QgsLineString):
        continue
    first_part = geom.geometryN(0)
    start = 0
    end = distance
    length = first_part.length()

    while start < length:
        new_geom = first_part.curveSubstring(start,end)

        output_feature = input_feature
        output_feature.setGeometry(QgsGeometry(new_geom))
        sink.addFeature(output_feature)

        start += distance
        end += distance

There’s a lot here, but really the guts of this algorithm breaks down to one line:

new_geom = first_part.curveSubstring(start,end)

Basically, a new geometry is created for each trimmed section in the output layer by calling the “curveSubstring” method on the input geometry and passing it a start and end distance along the input line. This returns the portion of that input LineString (or CircularString, or CompoundCurve) between those distances. The PyQGIS API nicely hides the details here – you can safely call this one method and be confident that regardless of the input geometry type the result will be correct.

Unfortunately, while calling the “curveSubstring” method is elegant, all the code surrounding this call is not so elegant. As a (mostly) full-time QGIS developer myself, I tend to look over oddities in the API. It’s easy to justify ugly API as just “how it’s always been”, and over time it’s natural to develop a type of blind spot to these issues.

Let’s start with the first ugly part of this code:

geom = input_feature.geometry().constGet()
if isinstance(geom, QgsLineString):
    continue
first_part = geom.geometryN(0)
# chop first_part into sections of desired length
...

This is rather… confusing… logic to follow. Here the script is fetching the geometry of the input feature, checking if it’s a LineString, and if it IS, then it skips that feature and continues to the next. Wait… what? It’s skipping features with LineString geometries?

Well, yes. The algorithm was written specifically for one workshop, which was using a MultiLineString layer as the demo layer. The script takes a huge shortcut here and says “if the input feature isn’t a MultiLineString, ignore it — we only know how to deal with multi-part geometries”. Immediately following this logic there’s a call to geometryN( 0 ), which returns just the first part of the MultiLineString geometry.

There’s two issues here — one is that the script just plain won’t work for LineString inputs, and the second is that it ignores everything BUT the first part in the geometry. While it would be possible to fix the script and add a check for the input geometry type, put in logic to loop over all the parts of a multi-part input, etc, that’s instantly going to add a LOT of complexity or duplicate code here.

Fortunately, this was the perfect excuse to improve the PyQGIS API itself so that this kind of operation is simpler in future! Nathan and I had a debrief/brainstorm after the workshop, and as a result a new “parts iterator” has been implemented and merged to QGIS master. It’ll be available from version 3.6 on. Using the new iterator, we can simplify the script:

geom = input_feature.geometry()
for part in geom.parts():
    # chop part into sections of desired length
    ...

Win! This is simultaneously more readable, more Pythonic, and automatically works for both LineString and MultiLineString inputs (and in the case of MultiLineStrings, we now correctly handle all parts).

Here’s another pain-point. Looking at the block:

new_geom = part.curveSubstring(start,end)
output_feature = input_feature
output_feature.setGeometry(QgsGeometry(new_geom))

At first glance this looks reasonable – we use curveSubstring to get the portion of the curve, then make a copy of the input_feature as output_feature (this ensures that the features output by the algorithm maintain all the attributes from the input features), and finally set the geometry of the output_feature to be the newly calculated curve portion. The ugliness here comes in this line:

output_feature.setGeometry(QgsGeometry(new_geom))

What’s that extra QgsGeometry(…) call doing here? Without getting too sidetracked into the QGIS geometry API internals, QgsFeature.setGeometry requires a QgsGeometry argument, not the QgsAbstractGeometry subclass which is returned by curveSubstring.

This is a prime example of a “paper-cut” style issue in the PyQGIS API. Experienced developers know and understand the reasons behind this, but for newcomers to PyQGIS, it’s an obscure complexity. Fortunately the solution here was simple — and after the workshop Nathan and I added a new overload to QgsFeature.setGeometry which accepts a QgsAbstractGeometry argument. So in QGIS 3.6 this line can be simplified to:

output_feature.setGeometry(new_geom)

Or, if you wanted to make things more concise, you could put the curveSubstring call directly in here:

output_feature = input_feature
output_feature.setGeometry(part.curveSubstring(start,end))

Let’s have a look at the simplified script for QGIS 3.6:

for input_feature in enumerate(features):
    geom = feature.geometry()
    for part in geom.parts():
        start = 0
        end = distance
        length = part.length()

        while start < length:
            output_feature = input_feature
            output_feature.setGeometry(part.curveSubstring(start,end))
            sink.addFeature(output_feature)

            start += distance
            end += distance

This is MUCH nicer, and will be much easier to explain in the next workshop! The good news is that Nathan has more niceness on the way which will further improve the process of writing QGIS Processing script algorithms. You can see some early prototypes of this work here:

So there we go. The process of writing and delivering a workshop helps to look past “API blind spots” and identify the ugly points and traps for those new to the API. As a direct result of this FOSS4G/SOTM Oceania 2018 Workshop, the QGIS 3.6 PyQGIS API will be easier to use, more readable, and less buggy! That’s a win all round!

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Add Realistic Mist and Fog to Topography in QGIS 3.2

I recently came across a great tutorial by in which he demonstrated how to create map of Switzerland in the style of Edward Imhof, the famed Swiss cartographer renowned for his hand painted maps of Switzerland and other mountainous regions of the world. John’s map used traditional hillshading, multidirectional hillshading and crucially, a translucent topographic layer that created a mist like appearance he likened to the sfumato technique used by painters since the Renascence.

I followed John’s tutorial in QGIS 3.2 and I was quite pleased with the initial result below. However, the process creating it is a bit too complicated for a tutorial so I set about simplifying the process and rather than imitating Imhof’s distinct style, my goal this time is realism.

The heart of the effect involves the very clever idea of using the topographic layer as a subtle opacity mask to simulate mist, fog and atmospheric haze. Have a look at the image below taken on March 17th, 2005 by NASA’s Terra satellite. This is the industrialised Po valley of northern Italy, surrounded by the Alps and Apennine Mountains that rise above the valley’s hazy pollution. The haze adds a sense of depth to the surrounding hills and mountains. It’s not uncommon to see fog and pollution in satellite imagery that gives way to the clear air in high mountains e.g. northern India and Nepal, China, Pakistan and India. Creating a similar mist effect in QGIS is actually quite simple.

First download topography for the Alps and Po region (a 68.55 Mb GeoTiff file derived from freely available EU-DEM data I resampled from 25 to 100m resolution). Next, make sure you have the plugin QuickMapServics (QMS) installed (menu Plugins – Manage and Install Plugins). This great plugin provides access to over 1000 basemaps.

Load the GeoTiff file into QGIS (Raster – Load) and rename the layer Hillshade. Right click the layer to open the Layer Properties window. In the Symbology panel, next to Render Type, choose Hillshade. Change the altitude to 35 degrees, Azimuth to 300 degrees and Z Factor of 1.5 (illuminating the landscape from the top left). Finally, change the Blending mode to Multiply. Click OK to close the dialogue.

To add the basemap layer, Esri World Imagery (Clarity), type “ESRI clarity” in the QMS search bar to find and add the basemap; Go to View – Panels and activate the QMS search bar if it isn’t initially visible. Make sure it’s the bottommost layer.

Oh, that’s a bit disappointing, we only increased the relief little a bit. It’s missing the vitally important mist layer.

To create mist, right click the Hillshade layer and choose Duplicate. Rename the new layer Mist and make sure it’s above the Hillshade layer. Now open the Layer Properties window of the layer, we’re going edit it’s attributes to make it look like mist.

Change the Render type to Singleband Pseudocolor and use 0 and 3000 for the min and max values (limiting maximum latitude of the mist to 3000 meters). Then open the colour ramp window by clicking on the Color ramp and enter these values:

  • Left Gradient – HSV 215 15 50 and 75% transparency
  • Right Gradient – HSV 215 15 50 and 0% transparency

Close the Color Ramp dialogue. In the Layer Properties window, and this is very important, change the Blending mode to Lighten. Click OK to close the Layer Properties window.

Wow, we have mist!

The mist effect looks great. It certainly adds a lot of realism to the topographic map, it now looks quite like NASA’s images. This is just a quick and basic map so there’s lots of scope to improve the effect. Play around with the colour of the mist layer and its opacity, or even brighten the Hillshade layer underneath. See what effects these changes have.

Here’s another example below. In this example I duplicated the hillshade layer and set the second hillshade layer to Multidirectional Hillshading (yes, QGIS 3.2 has Multidirectional Hillshading). I then adjusted the transparency of both hillshade layers so they blended together nicely. I then replaced the basemap with another duplicated topography layer that I coloured using the gradient sd-a (by Jim Mossman, 2005) using the cpt-city plugin. And lastly, I doubled the opacity of the mist layer turning it into a milky fog. I think it looks great!

What next? Well, there’s lots of possibilities. Perhaps download Martian topography and add mist to the bottom of Valles Marineris?

References:

Eduard Imhof – Biography

TV documentary about Eduard Imhof

The Map as an Artistic Territory: Relief Shading Works and Studies by Eduard Imhof

Haze in northern Italy – NASA Terra Satellite

Tzvetkov, J., 2018. Relief visualization techniques using free and open source GIS tools. Polish Cartographical Review, 50(2), pp.61-71.
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OpenCL acceleration now available in QGIS

What is OpenCL?

From https://en.wikipedia.org/wiki/OpenCL:

OpenCL (Open Computing Language) is a framework for writing programs that execute across heterogeneous platforms consisting of central processing units (CPUs), graphics processing units (GPUs), digital signal processors (DSPs), field-programmable gate arrays (FPGAs) and other processors or hardware accelerators. OpenCL specifies programming languages (based on C99 and C++11) for programming these devices and application programming interfaces (APIs) to control the platform and execute programs on the compute devices. OpenCL provides a standard interface for parallel computing using task- and data-based parallelism.

Basically, you write a program and you execute it on a GPU (or, less frequently, on a CPU or on a DSP) taking advantage of the huge parallel programming capabilities of the modern graphic cards.

Depending on many different factors, the speed gain can vary to a great extent, but it is typically around one order of magnitude.

How QGIS benefits from OpenCL?

The work I’ve done consisted in integrating OpenCL support into QGIS and writing all the utilities to load, build and run OpenCL programs.

For now, I’ve ported the following QGIS core algorithms, all of them are availabe in processing:

  • slope
  • aspect
  • hillshade
  • ruggedness

Since the framework to support OpenCL is now in place, I think that more algorithms will be ported over the time.

During this development, even if was not in scope, the hillshade renderer has been optimized for speed and it can also benefit of OpenCL acceleration.

How to activate OpenCL support

OpenCL support is optional and opt-in, to use it, you need to activate it into the QGIS options dialog like shown in the screenshot below:

How much performance gain can I expect?

Well, YMMV, but here are some figures for a big DEM raster, low values mean faster execution.

GDAL means CPU execution using the GDAL processing algorithm.

How to install the OpenCL drivers?

Of course it depends on your specific hardware and on your O.S., AMD, NVidia and Intel have different distributions channels, in general the driver for your graphic card will also provide the OpenCL driver, if your GPU is compatible, if OpenCL is not available on your current machine, try to Google for OpenCL, your O.S. and graphic card.

If there is no OpenCL support for your graphic card, you might try to install a driver for your GPU (Intel for example provides them) and you will probably have a decent acceleration even if not as much as you can get on a real graphic card.

This fact worths some more explanation: you might ask your self why running and algorithm directly on the CPU and running it on the same CPU but using OpenCL would make any difference and the reason why it is generally faster by using OpenCL is that OpenCL will run the algorithm in parallel on all cores of your CPU, while a normal application (and QGIS does not make an exception here) will use a single core.

How to build QGIS with OpenCL support on Ubuntu

Just a quick note: you’ll need to install the OpenCL headers and the ICD library:

sudo apt-get install opencl-headers ocl-icd-opencl-dev

 

Credits

I started this work as a proof of concept in my spare time (that it is not much, lately) and when I realized that it was promising, I submitted a QGIS grant proposal in order to allocate some working time to port more algorithms, write tests and polish the implementation.

This work would not be possible without all the generous sponsors and donors that feed the QGIS grant program year after year, many thanks to the QGIS community for this amazing support!

Jürgen Fischer was as usual very helpful and took care of the windows builds, now available in OSGeo4W packages.

Nyall Dawson helped with the code review and with testing the implementation on different cards and machines.

Matthias Kuhn reviewed the code.

Even Rouault pointed me to some highly efficient GDAL algorithm optimizations that I’ve been able to integrate in QGIS.

 

 

The post OpenCL acceleration now available in QGIS first appeared on Open Web Solutions, GIS & Python Development.

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Create a QGIS vector data provider in Python is now possible

 

Why python data providers?

My main reasons for having Python data provider were:

  • quick prototyping
  • web services
  • why not?

 

This topic has been floating in my head for a while since I decided to give it a second look and I finally implemented it and merged for the next 3.2 release.

 

How it’s been done

To make this possible I had to:

  • create a public API for registering the providers
  • create the Python bindings (the hard part)
  • create a sample Python vector data provider (the boring part)
  • make all the tests pass

 

First, let me say that it wasn’t like a walk in the park: the Python bindings part is always like diving into woodoo and black magic recipes before I can get it to work properly.

For the Python provider sample implementation I decided to re-implement the memory (aka: scratch layers) provider because that’s one of the simplest providers and it does not depend on any external storage or backend.

 

How to and examples

For now, the main source of information is the API and the tests:

To register your own provider (PyProvider in the snippet below) these are the basic steps:

metadata = QgsProviderMetadata(PyProvider.providerKey(), PyProvider.description(), PyProvider.createProvider)
QgsProviderRegistry.instance().registerProvider(metadata)

To create your own provider you will need at least the following components:

  • the provider class itself (subclass of QgsVectorDataProvider)
  • a feature source (subclass of QgsAbstractFeatureSource)
  • a feature iterator (subclass of QgsAbstractFeatureIterator)

Be aware that the implementation of a data provider is not easy and you will need to write a lot of code, but at least you could get some inspiration from the existing example.

 

Enjoy wirting data providers in Python and please let me know if you’ve fond this implementation useful!

The post Create a QGIS vector data provider in Python is now possible first appeared on Open Web Solutions, GIS & Python Development.

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QGIS 3 Server deployment showcase with Python superpowers

Recently I was invited by the colleagues from OpenGIS.ch to lend a hand in a training session about QGIS server.

This was a good opportunity to update my presentation for QGIS3, to fix a few bugs and to explore the powerful capabilities of QGIS server and Python.

As a result, I published the full recipe of a Vagrant VM on github: https://github.com/elpaso/qgis3-server-vagrant

The presentation is online here: http://www.itopen.it/bulk/qgis3-server/

What’s worth mentioning is the sample plugins (I’ll eventually package and upload them to the official plugin site):

 

The VM uses 4 different (although similar) deployment strategies:

  • good old Apache + mod_fcgi and plain CGI
  • Nginx + Fast CGI
  • Nginx + standalone HTTP Python wrapped server
  • Nginx + standalone WSGI Python wrapped server

Have fun with QGIS server: it was completely refactored in QGIS 3 and it’s now better than ever!

 

The post QGIS 3 Server deployment showcase with Python superpowers first appeared on Open Web Solutions, GIS & Python Development.

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Use your android phone’s GPS in QGIS

Do you want to share your GPS data from your phone to QGIS? Here is how:   QGIS comes with a core plugin named GPS Tools that can be enabled in the Plugin installer dialog:   There are several ways to forward data from your phone and most of them are very well described in the QGIS manual page: https://docs.qgis.org/testing/en/docs/user_manual/working_with_gps/plugins_gps.html What I’m going to describe here is mostly useful when your phone and your host machine running QGIS are on the same network (for example they are connected to the same WiFi access point) and it is based on the simple application GPS 2 NET   Once the application is installed and started on your phone, you need to know the IP address of the phone, on a linux box you can simply run a port scanner and it will find all devices connected to the port 6000 (the default port used by GPS 2 NET):  
# Assuming your subnet is 192.168.9

nmap -p 6000 192.168.1.*

Nmap scan report for android-8899989888d02271.homenet.telecomitalia.it (192.168.99.50)
Host is up (0.0093s latency).
PORT STATE SERVICE
6000/tcp open X11

  Now, in QGIS you can open the plugin dialog through Vector -> GPS -> GPS Tools and enter the IP address and port of your GPS device:   Click on Connect button on the top right corner (mouse over the gray square for GPS status information)   Start digitizing!

The post Use your android phone’s GPS in QGIS first appeared on Open Web Solutions, GIS & Python Development.

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Welcome QGIS 3 and bye bye Madeira

Last week I’ve been in Madeira at the hackfest, like all the past events this has been an amazing happening, for those of you who have never been there, a QGIS hackfest is typically an event where QGIS developers and other pasionate contributors like documentation writers, translators etc. gather together to discuss the future of their beloved QGIS software. QGIS hackfest are informal events where meetings are scheduled freely and any topic relevant to the project can be discussed. This time we have brought to the table some interesting topics like:
  • the future of processing providers: should they be part of QGIS code or handled independently as plugins?
  • the road forward to a better bug reporting system and CI platform: move to gitlab?
  • the certification program for QGIS training courses: how (and how much) training companies should give back to the project?
  • SWOT analysis of current QGIS project: very interesting discussion about the status of the project.
  • QGIS Qt Quick modules for mobile QGIS app
Tehre were also some mentoring sessions where I presented:
  • How to set up a development environment and make your first pull request
  • How to write tests for QGIS (in both python and C++)
  At this link you can find all the video recordings of the sessions: https://github.com/qgis/QGIS/wiki/DeveloperMeetingMadeira2018   Here is a link to the Vagrant QGIS developer VM I’ve prepared for the session: https://github.com/elpaso/qgis-dev-vagrant/   I’ve got a good feedback from other devs about my sessions and I’m really happy that somebody found them useful, one of the main goals of a QGIS hackfest should really be to help other developers to ramp up quicly into the project. Other than that, I’ve also find the time to update to QGIS 3.0 some of my old plugins like GeoCoding and QuickWKT.   Thanks to Giovanni Manghi and to Madeira Government for the organizazion and thanks to all QGIS sponsors and donors!   About me: I started as a QGIS plugin author, continued as the developer of the plugin official repository at https://plugins.qgis.org and now I’m one of the top 5 QGIS core contributors. After almost 10 years that I’m in the QGIS project I’m now not only a proud member of the QGIS community but also an advocate for the open source GIS software movement.

The post Welcome QGIS 3 and bye bye Madeira first appeared on Open Web Solutions, GIS & Python Development.

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