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Sat Apr 19 14:30:10 2014

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QGIS Planet

Slides – Scottish QGIS User Group Meeting

An introduction from Ross McDonald to the inaugral QGIS user group meeting in Scotland.

Neil Benny from thinkWhere getting passionate about QGIS and open source spatial software.

Martin Dobias from Lutra showing us the super performance enhancements coming in the next version of QGIS.

Charley Glynn from Ordnance Survey demonstrating some of the map eye candy they’re producing with QGIS.

Pete Wells from Lutra showing us how to use Python with QGIS.

Videos of the talks will be posted here including Heikki Versanto showing how to connect to a huge variety of data sources.


QGIS PT users group: Portuguese speaking community

It’s with an enormous pleasure that we announce what we believe to be a very important step for the QGIS Portuguese speaking community, the creation of the QGIS PT users group. The QGIS PT users group arise from the notorious growth of QGIS usage  in Portugal, with the objective of become a platform for sharing […]

Using OSM POIs in QGIS

Extracting POIs from OpenStreetMap is reasonably simple using Overpass API. A very convenient way to construct the query is to use a query builder which allows you to select the area of interest and builds queries for different servers.

xapi_query_builder

Of course you can fine-tune the query further. For example, you can add multiple key-value pairs to the query. I used the following query to select all Billa supermarkets:

http://www.overpass-api.de/api/xapi?*[shop=supermarket][name=Billa][bbox=15.96725,48.0432,16.79947,48.40915]

Note to * in the query? It means that I’m querying all kinds of features: nodes, ways, and relations.

Save the server response to a .osm file. This file can be loaded into QGIS using simple drag-and-drop or Add Vector Layer. A dialog will open where you can select the type of features you want to load from the file. You can simply use Select All and OK to load everything.

add_osm_file

My supermarket POIs came in two types: points and multipolygons. To style them both with nice supermarket SVG icons, I decided to use a Centroid fill with the SVG marker for the polygon layer:

osm_pois_billa

Open data and open source GIS … nice :-)


Topology in QGIS

Introduction

Topology rules define the permissible relationships of features within a given GIS layer or between features in two different GIS layers. An example is that features in a road dataset must be connected to other roads at both ends, unless the road is specified as a dead end street.

Advantage of topology over queries

A lot of the checks that topology rules carry out could be achieved using spatial queries. You may have to use queries if the GIS software you’re using doesn’t have a topology feature.

Topology rules have the advantage that they only need be created once and then they can check your work as you go.

Queries would need to be re-created each time they are run. They can be saved, depending on the GIS being used, but this is still more time consuming and it is a task that must be carried out separately at the end of a work session.

Rules

QGIS 2.2 topology tool has the following rules pre-defined:-

  • End points must be covered by (e.g. a railway line usually begins and ends at a station)
  • Must contain (e.g. a building polygon must contain at least one address point seed)
  • Must not have dangles (a line must begin and end at another line)
  • Must not have duplicates (each feature should be unique, e.g. postcode areas)
  • Must not have gaps (e.g. administrative area polygons cannot have gaps)
  • Must not have invalid geometries
  • Must not have multi-part geometries (each feature should be a separate entry)
  • Must not overlap (e.g. administrative area polygons cannot overlap each other)
  • Must not overlap with (a feature from layer must not overlap with another layer)

Example 1 – Roads must not have dangles

The following example uses the “Must not have dangles” rule to identify polylines from a roads dataset that are not snapped to other lines. Roads usually begin and end at a junction with another road, so this is a useful rule to identify where lines were not correctly snapped together.

To create and validate a Topology Rule

  • Open the Topology Panel, by selecting Vector menu, Topology Checker, Topology Checker
  • The Topology Panel appears in the lower right corner of the QGIS desktop window

Image

  • Press the Configure button to open the Topology Rule Settings dialog
  • The top of the box will have 2 or 3 pull down boxes depending on the layer and rule that is chosen. Use these to build the rule and then press the Add Rule button.

Image

  • Press OK when done, the dialog box closes and the window returns to the QGIS Desktop.
  • Press either the Validate All or Validate extent, depending on whether you wish to validate the entire dataset or just the current view extent.
  • The errors will be listed. Double click on a row will make the map window zoom and pan to the error.

Image

 


Formação em SIG Open Source com QGIS (Quantum GIS) em Moura, 28-29-30 Maio 2014

A Faunalia, em colaboração com a ENCPB (Escola Nacional de Caça, Pesca e Biodiversidade), Comoiprel e Câmara Municipal de Moura, organiza um curso de SIG Open Source com QGIS (Quantum GIS) nos dias 28-29-30 Maio 2014. Para informações e inscrições contactar: ENCPB (Escola Nacional de Caça, Pesca e Biodiversidade) E-Mail: encpb.moura@gmail.com Telefone: 285251354   Programa […]

Reporting back from the Vienna Code Sprint

Today was the last day of the Vienna code sprint which brought together OSGeo developers from many projects. It’s been a great week thanks to organizers and sponsors!

The QGIS team was extremely busy working on the project’s web infrastructure (e.g. new plugins.qgis.org website) as well as hunting down and fixing bugs.

Check out some impressions on twitter.

qgis23_vienna

More pictures on the official blog: vienna2014.sprint.osgeo.org


OSGeo Code Sprint, Vienna

This is how OSGeo happens.  These are the folk who bring us a lot of that open-source geo-spatial goodness. You can follow the code sprint on Twitter using the hashtags #csprint and #viennacodesprint14

 


Scottish QGIS User Group

scottish flagThe inaugural Scottish QGIS user group meeting is being planned and organised for mid-March next year.  If you would like to participate, I am looking for user presentations, case studies, map displays and practical demos and tutorials.

The event will be held in Stirling and will be a full day of networking and open-source geo-goodness.  Full details will go out in the new year and will be available through Eventbrite, this blog, the Google+ group, Twitter and probably a heap of other channels.  After the success of the English and the Welsh events we are hoping the Scottish event will raise the bar even higher.  Please use the contact form to get in touch with me, Ross McDonald.


How the West was Won (or QGIS rocks!)

gazetteer search list!<tl><dr>

Local Authorities work with people and assets. Most people have an address and assets are mostly located somewhere. As my old geography teacher used to say, “everything has geography, geography is everything”. For people who work in Local Authorities being able to find an accurate and up-to-date address easily is key to being able to deliver a service quickly and efficiently. If GIS officers had their way even more of the Council back office systems across the country would hook up to the corporate GI database and do cool stuff with spatial information.

At the recent AGI GeoCom and FOSS4G conferences in Nottingham during Maptember QGIS 2.0 was launched and garnered a lot of attention from people interested in finding solutions to save money and time and still deliver great results. I came away with a resolution to push for the use of QGIS at work in an attempt to get a desktop GIS onto more desktops while not breaking the bank. I had also met Simon Miles (@geosmiles) and eagerly followed his talk of creating a hybrid GI infrastructure using a mix of open-source and proprietary software.

QGIS fitted the bill with its extensive range of functionality, growing list of available plugins, super easy connectivity to a range of data sources including Oracle, SQL Server and PostGIS, all of which we use. The one thing it was lacking was a search plugin to let the users search the corporate address gazetteer for postal address and street names. Our existing GIS has such a plugin and it works well but not with the imminent upgrades. There had to be something that could connect to the gazetteer table in our PostGIS database, search and display an address.

qgis gazetteer pluginEnter the QGIS Gazetteer Plugin developed by Astun Technology, Nathan Woodrow and Matt Walker. Add some keen peeps from the UK QGIS User Group and some social networking and stuff begins to happen.

After downloading and installing the plugin I soon hit a brick wall – or rather a firewall – the security at work wouldn’t let the Yahoo and Geonames gazetteers work and we don’t have Astun’s iShareGIS software stack. I delved into the code to see if I could work out what was happening and hit another wall – how does this Python stuff work? Nought for two after one over.

After some chat on the UK QGIS Google+ group I found some people in Local Government across the UK who have managed to get the plugin to work and work well.  Simon Miles (Royal Borough of Windsor and Maidenhead), Kevin Williams (Neath-Port Talbot) and Matt Travis (Dartmoor National Park) rallied to my call and soon I had some code in my grubby mitts.  An hour after that I had a working plugin searching our address and street gazetteers, postcodes and planning applications.  Listed buildings, building warrants and others soon followed.  I shared the plugin with some of our power users and they were very impressed and have even started asking for enhancements.

This whole process is a great example of how a User Group can work when coupled with FOSS4G fans, social media, open-source software and a common problem to solve.  Being able to present a working solution to users and managers in just a few days certainly strengthens the case for using QGIS alongside the traditional GIS tools and maybe, in time, replacing them.

What follows is a rather more technical description of the installation and configuration of just about the single most useful application a Council officer could ask for. If you want the short version and can do the tech stuff then go to https://github.com/mixedbredie/qgis-gazetteer-search and get it, otherwise hang in there to the end…

What you need:

1. QGIS 2.0 installed

2. the QGIS Gazetteer plugin installed

3. a PostGIS database with some gazetteer tables

4. an Apache2 web server

how-it-works

1. QGIS

Install QGIS 2.0 – I used the standalone installer from http://www.qgis.org/en/site/forusers/download.html

2. QGIS Gazetteer Plugin

Install the QGIS Gazetteer plugin from https://github.com/AstunTechnology/QGIS-Gazetteer-Plugin by downloading the zip file and extracting into your .qgis2 folder. This is located at

C:\Documents and Settings\<Username>\.qgis2\python\plugins\ (Windows XP) or 
C:\Users\<Username>\.qgis2\python\plugins\ (Windows 7+).

Make sure that the extracted directory is called “gazetteersearch”. Matt Walker (@_walkermatt) has upgraded the plugin to work with QGIS 2.0 and added a few enhancements like an OpenStreetMap search.

In the “gazetteers” sub directory there a “config.ini” file which needs to be edited to list the datasets we want to search. I’ll show how to connect to the address and street gazetteers and a table of postcode areas.

I deleted the GeoNames, Yahoo and AstunTechnology lines and inserted the following:

[LLPG]
gazetteer:llpg
[LSG]
gazetteer:lsg
[Postcode]
gazetteer:postcodes

Create three files in the gazetteers folder – llpg.py, lsg.py and postcodes.py

In the llpg.py file put:

import json
import collections
url = "http://10.135.1.69/cgi-bin/llpg_pg.py"
params = {
    'address': '##searchstring##'
}
def parseRequestResults (data):
json_result = json.loads (data)
    for item in json_result:
        result = collections.namedtuple ('Result', ['description','x','y','zoom', 'epsg'])
        result.description = item['address']
        result.x = float (item['easting'])
        result.y = float (item['northing'])
        result.zoom = 1250
        result.epsg = 27700
        yield result

In the lsg.py file put:

import json
import collections
url = "http://10.12.345.678/cgi-bin/lsg_pg.py"
params = {
    'address': '##searchstring##'
}
def parseRequestResults (data):
json_result = json.loads (data)
for item in json_result:
        result = collections.namedtuple ('Result', ['description','x','y','zoom', 'epsg'])
        result.description = item['address']
        result.x = float (item['easting'])
        result.y = float (item['northing'])
        result.zoom = 2500
        result.epsg = 27700
        yield result

In the postcodes.py file put:

import json
import collections
url = "http://10.12.345.678/cgi-bin/postcodes_pg.py"
params = {
    'postcode': '##searchstring##'
}
def parseRequestResults (data):
    json_result = json.loads (data)
    for item in json_result:
        result = collections.namedtuple ('Result', ['description','x','y','zoom', 'epsg'])
        result.description = item['postcode']
        result.x = float (item['easting'])
        result.y = float (item['northing'])
        result.zoom = 2500
        result.epsg = 27700
        yield result

You need to set the correct server IP address in the URL and link to the correct file in the cgi-bin. You can also set the zoom scale for the results and I use ESPG:27700 as everything we have is in British National Grid.

If you restart QGIS and enable the plugin you’ll see there are now four search options in the drop-down list. Right, now to make sure PostGIS has the correct information.

3. PostGIS Database

The installation and configuration of PostgreSQL and PostGIS is more than this post is going to address but you’ll need to have one. With some tables in it with some data that can be searched. We load our address and street gazetteers into PostGIS on a daily basis and these tables are used by the plugin for searching and displaying records. Our tables have a UPRN (Unique Property Reference Number) field and an ADDRESS field with a full address in it (name number street town locality postcode). The address gazetteer has a point geometry. The street gazetteer has a USRN (Unique Street Reference Number) and a NAME field with the full descriptive name of the street in it. It has a line geometry. Almost any table can be searched as long as it has a unique id, a text field for searching, and some geometry.

Our address gazetteer already had the correct fields in so nothing had to be done but the street gazetteer needed some changes. I created a view of the streets to change the name of the fields to fit with what the plugin was expecting:

CREATE OR REPLACE VIEW angusdata.search_lsg_streets AS
SELECT a.usrn AS uprn,
btrim(pg_catalog.concat('usrn:', btrim(a.usrn::text), ' ', btrim(a.street::text), ' ', btrim(a.locality::text), ' ', btrim(a.town::text))) AS address,a.geometry
FROM lsg_streets a;

This changes the USRN field to UPRN and concatenates USRN, STREET, LOCALITY and TOWN to create an ADDRESS field and then adds the geometry.

The Postcodes table has polygon geometry and a postcode field and the python script that creates the web service has been tweaked to work with this. The next section will explain how to create the web services on Apache2.

4. Apache

I have a local Apache2 webserver running on my PC but it’s pretty easy to get one set up on server if you chat to the right people :-) so get one installed (http://www.apachehaus.com/cgi-bin/download.plx). The plugin uses the web services running in the Apache2 cgi-bin to connect to the PostGIS database to query the gazetteers. You’ll also need to have Python (http://www.python.org/download/releases/2.7.5/) installed on the same machine. And the Python psycopg2 module (http://www.stickpeople.com/projects/python/win-psycopg/).

First up, the Apache2 server needs to be configured to allow use of the cgi-bin. Edit the httpd.conf file and make the following changes.

Uncomment the following lines to enable the modules:

LoadModule access_compat_module modules/mod_access_compat.so
LoadModule cgi_module modules/mod_cgi.so
LoadModule proxy_fcgi_module modules/mod_proxy_fcgi.so
LoadModule rewrite_module modules/mod_rewrite.so

Set the server name to its IP address:

ServerName 10.12.345.678:80

Allow access to the server:

<Directory />
  Options Indexes FollowSymLinks ExecCGI
  AllowOverride All
  Order allow,deny
  Allow from all
  Require all granted
</Directory>

Set the file that Apache will serve if a directory is requested:

<IfModule dir_module>
  DirectoryIndex index.html index.htm index.php index.php3
</IfModule>

Allow access to the CGI directory and enable it to handle python scripts:

<Directory "${SRVROOT}/cgi-bin">
  Options Indexes FollowSymLinks ExecCGI
  AllowOverride All
  Order allow,deny
  Allow from all
  Require all granted
  AddHandler cgi-script .cgi .py
</Directory>

This is a pretty basic configuration and it could probably be improved but it works on my system.

Then in the CGI-BIN directory create some files, one for each web service and to match the gazetteers listed in the config file. I created three files called llpg_pg.py, lsg_pg.py and postcodes_pg.py.

In the llpg_pg.py file the SQL query selects the records that match the search string and uses the point geometry of the records to return to the plugin.

#!D:/Python27/python.exe
# -*- coding: UTF-8 -*-
import cgi
import json
import psycopg2
sql = """select a.uprn, a.address, ST_X(a.geometry), ST_Y(a.geometry)
from angusdata.address_gazetteer a
where a.address ilike '%%' || (%(p_address)s) || '%%'
order by address"""
form = cgi.FieldStorage ()
connection = psycopg2.connect ("host='10.12.345.678' port='5432' dbname='postgisdb' user='username' password='password'")
cursor = connection.cursor ()
cursor.execute (sql, {"p_address": form["address"].value})
list = []
for record in cursor:
    data = dict (zip (["uprn", "address", "easting", "northing"], record))
    list.append (data)
print "Content-Type: application/json\n"
print json.dumps (list, indent = 4)

In the lsg_pg.py file the SQL query selects the records from the view and converts the line geometry to a centroid point.

#!D:/Python27/python.exe
# -*- coding: UTF-8 -*-
import cgi
import json
import psycopg2
sql = """select a.uprn, a.address, ST_X(ST_Centroid(a.geometry)), ST_Y(ST_Centroid(a.geometry))
from angusdata.search_lsg_streets a
where a.address ilike '%%' || (%(p_address)s) || '%%'
order by address"""
form = cgi.FieldStorage ()
connection = psycopg2.connect ("host='10.12.345.678' port='5432' dbname='postgisdb' user='username' password='password'")
cursor = connection.cursor ()
cursor.execute (sql, {"p_address": form["address"].value})
list = []
for record in cursor:
    data = dict (zip (["uprn", "address", "easting", "northing"], record))
    list.append (data)
print "Content-Type: application/json\n"
print json.dumps (list, indent = 4)

In the postcodes_pg.py file the SQL query turns the polygon geometry into a point geometry using the PostGIS ST_PointOnSurface function. The psycopg2 parameters have been tweaked to use the postcode tables fields.

#!D:/Python27/python.exe
# -*- coding: UTF-8 -*-
import cgi
import json
import psycopg2
sql = """select a.postcode, ST_X(ST_Pointonsurface(a.geometry)), ST_Y(ST_Pointonsurface(a.geometry))
from thirdparty.os_codepointpoly a
where a.postcode ilike '%%' || (%(p_postcode)s) || '%%'
order by postcode"""
form = cgi.FieldStorage ()
connection = psycopg2.connect ("host='10.12.345.678' port='5432' dbname='postgisdb' user='username' password='password'")
cursor = connection.cursor ()
cursor.execute (sql, {"p_postcode": form["postcode"].value})
list = []
for record in cursor:
    data = dict (zip (["postcode", "easting", "northing"], record))
    list.append (data)
print "Content-Type: application/json\n"
print json.dumps (list, indent = 4)

Make sure the #!shebang at the top of the python script has the correct path to your Python installation.

Check the Apache2 log files if there are any errors.

Right, we have QGIS installed with the gazetteer search plugin configured to use the new gazetteers.  The PostGIS tables and views are presenting the data in format required by the web services. The Apache2 server is configure to allow access and the python scripts are in the cgi-bin. Fire up QGIS, refresh the plugin and enter a search term and hit GO!  Awesome!  Mine works, at least.

None of this would have been possible without the UK QGIS group and the input from Matt, Kevin and Simon.  Big thanks to Matt Walker and Jo Cook for recent updates to the plugin.  Use the comments to tell us how to do it better.


FOSSGIS 2014 slides

Neues in QGIS 2.2

Nach dem lange erwarteten Release von QGIS 2.0 im September 2013, sind ab diesem Jahr neue Versionen im Viermonatszyklus geplant. Es werden die neuen Funktionen in QGIS 2.2, wie z.B. DB-Relationen mit verschachtelten Formularen, die erweiterten Methoden zur Transformierung geographischer Koordinatensysteme, zahlreiche Verbesserungen im Print Composer und ein komplett überarbeiteter DXF Export vorgestellt. Zusätzlich wird eine Vorschau auf das multithreaded Rendering gegeben und die neuen Mitglieder im Project Steering Committee vorgestellt

Links:

Mobile Kartenviewer mit Openlayers 3

Mit OpenLayers 3 steht eine komplette Neuentwicklung der funktionsreichen OpenLayers-Bibliothek zur Verfügung. Die verbesserte Unterstützung mobiler Geräte war ein primäres Ziel der neuen Version. Dieser Vortrag stellt den JQuery Mobile basierten OL3 Mobile Viewer vor, der erweiterte Funktionen wie automatische Kartenausrichtung oder Positionsnachführung bietet. Es wird auch ein Vergleich mit anderen Viewern, wie der auf Bootstrap und AngularJS aufbauenden Neuentwicklung von Swisstopo angestellt.

Links:

Two book recommendations

I recently finished reading two books which may be of interest to open-source GIS users – “PostGIS Cookbook” and “The PyQGIS Programmer’s Guide“, both of which I highly recommend:

PostGIS Cookbook

PostGIS CookbookI’ve been a fan of Stephen Mather’s blog for a while now, and have consistently found it to be a great source of trustworthy information and creative solutions to GIS problems. So when I first saw mention of his work on the PostGIS Cookbook I knew it would be a must-read for me. PostGIS is an essential part of my daily toolkit, and I’ll quickly devour any tutorial or guide which can lead me to better ways to put it to use. And that’s exactly what this book is! It’s full of tips and guides which has inspired me in a lot of techniques I’d never tried or even thought possible in PostGIS.

It’s important to point out that this book isn’t a training manual or beginner’s guide to PostGIS. It assumes readers are already familiar with using PostGIS and have a good understanding of GIS software in general. (If you’re looking for a book to start from scratch with PostGIS, PostGIS in Action is a better fit). I think that’s really what makes this book stand out though. There’s currently not a lot of books available covering PostGIS, and as far as I’m aware the PostGIS Cookbook is the only book available which is targeted to experienced PostGIS users.

Highlights for me are:

  • A great explanation and write up on optimised KNN filtering in PostGIS (something which often trips me up)
  • The detailed guide to topologically correct simplification of features
  • The exploration of PgRouting, which is a great introduction to PostGIS’ routing abilities
  • The “PostGIS and the web” chapter – I really wasn’t expecting this, but it’s quite eye opening (I’m going to have to do some digging into GeoDjango sometime)

The only criticism I have with this book is that it jumps around a lot between operating systems. While most of the code is provided for both Linux/OSX and Windows, there’s occasional examples which only have code for one specific operating system. It’s a little jarring and assumes the user is well versed in their particular operating system to workaround these omissions.

Overall, I strongly recommend the PostGIS Cookbook, and would consider it a must have for anyone serious about expanding their PostGIS abilities. (Also, looks like the publisher, Packt, have a two-for-one sale going at the moment, so it’s a good time to grab this title).

The PyQGIS Programmer’s Guide

The PyQGIS Programmer's GuideThe second book I’ve just finished reading is Gary Sherman’s “The PyQGIS Programmer’s Guide“. For those who are unaware, Gary was the original founder of QGIS back in 2002, so you can be confident that he knows exactly what he’s writing about. In The PyQGIS Programmer’s Guide  Gary has created an in-depth guide on how to get started with programming for QGIS using python. It takes readers all the way from simple scripts right through to developing QGIS plugins and standalone applications based on the QGIS API.

This book fills an important void in the literature available for QGIS. Previously, the PyQGIS Developer Cookbook was the only available guide for QGIS python scripting, and unfortunately it’s a little out-of-date now. PyQGIS scripting can be a steep learning curve and that’s why this book is so appreciated.

It would be valuable to have some python knowledge and experience prior to reading this book. While the “Python Basics” chapter quickly runs through an introduction to the language, the book makes no claims to be a comprehensive python tutorial. But if you’ve dabbled in the language before and have familiarity with the python way of doing things you’ll easily be able to follow along.

Highlights are:

  • The “Tips and Techniques” chapter, which is a great mini-reference for performing a range of common tasks in PyQGIS (including loading layers, changing symbol styles, editing feature attributes, etc).
  • A complete tutorial for creating a QGIS plugin
  • A guide to debugging PyQGIS code and plugins

I’d definitely recommend that anyone who wants to get started with PyQGIS start with Gary’s work – you’ll find it the perfect place to begin.

Re-Projecting Vector Layers in QGIS

QGIS can re-project a layer using both on-the-fly re-projection for the current session; and by saving a copy of the layer with a new Co-ordinate Reference System (CRS) defined.

On the fly

This is useful when a layer only needs to be re-projected for the current session.

Add the layer. If the CRS is known, QGIS will re-project it if necessary.

To check which CRS has been specified for the layer, right click on the layer in the Layers Panel, select Properties, and then select the General tab.

QGIS Layers Property

QGIS Layers Property

 

To save a new copy

It is a good practice to save a copy of a layer once it has been re-projected. This is to ensure the new CRS and transformations are permanently assigned to it. This avoids transformation errors when it is added to later map documents.

To save a copy:-

  1. Right click on the layer in the Layers Panel , select Save As.
  2. In the Save Vector layer as dialog, specify the filename, plus the new Co-ordinate Reference System. It is possible to add a symbology reference scale and new attributes. It is a good idea to add the new layer to the map to check it is correctly projected.
QGIS Save Vector Layer Dialog

QGIS Save Vector Layer Dialog


3D viz with QGIS & three.js

If you are looking for a tool to easily create 3D visualizations of your geodata, look no further! Qgis2threejs is a plugin by Minoru Akagi which exports terrain data combined with the map canvas image and optional vector data to an html file which can be viewed in 3D in any web browser which supports WebGL. To do that, this plugin uses the Three.js library.

This is the result of my first experiments with Qgis2threejs. In the following sections, I will show the steps to reproduce it.

Türkenschanzpark, Vienna

click for the interactive version (requires WebGL-capable browser)

1. The data

The building blocks of this visualization are:

  • elevation data and the hillshade derived from this data
  • a base map (WMTS from basemap.at in my case)
  • OSM building data provided by Geofabrik and
  • tree data from the city of Vienna

Load all datasets into QGIS.

2. Preparing the map

Qgis2threejs will overlay the map (as rendered in the QGIS map area) on top of the elevation model. You can combine any number of layers to create your map. I just loaded a basemap.at WMTS and a hillshade layer. To add a nice tree shadow effect, I also added the tree layer (dark grey, 50% transparency, multiply blending).

tuerkenschanzpark_map

3. Preparing the vector features

The vector features in the visualization are buildings and trees. The buildings are based on an OSM building layer. The trees are create from two point layers: one point layer to create the tree trunks (cylinder shape) and a duplicate of this point layer to create the tree crowns (sphere shape).

Load the data and choose the desired fill colors.

4. Using Qgis2threejs

Now we can start Qgis2threejs. The first tab is used to configure the terrain. Just pick the correct elevation data layer. I didn’t modify any of the other default settings.

qgis2threejs_dem

The second tab provides the settings for the vector data. As mentioned in the previous section, the trees are created from two point layers and the buildings are based on a polygon layer. The tree crowns are spheres with a radius size 3 and a z value of 5 above the surface. The tree trunks are cylinders. Finally, the buildings have a height of 10.

qgis2threejs_vector

That’s it! Just press “run” and wait. When the export is finished, your default browser (or a different one, if you specify another one in the plugin settings) will open automatically and display the results.
The visualization is interactive. You can tilt the visualization using the left mouse button, pan using the right mouse button, and zoom using the mouse wheel. I found that Firefox used around 1.6 GB of RAM to render this example.

5. Share your visualization

In the browser window, you will see where Qgis2threejs stored the html and associated Javascript files. To share your visualization, you just need to copy these files onto a webserver.

I would love to see what you come up with. Please share a link in the comments.


Build and deploy c++ QGIS app on windows

After a lot of troubles, I managed to compile and deploy a QGIS c++ app on windows. This small guide will describe the steps I followed. This has been tested on win xp and windows 7, both in 32 bits.

Development environment

Your app must be built using MSVC 9.0 (2008) since QGIS in OSGeo’s package was built with it. Hence, MinGW cannot be used.

  1. Install Microsoft Visual Studio Express 2008.
  2. Install QGIS and Qt libs using OSGeo4W installer
  3. Install Qt Creator
  4. If you want a debugger,you should install CDB. This can be achieved by installing Windows SDK environment. In the installation process, only select Debugging toos for windows.

I wasn’t able to use the compiler yet, so I am not 100% sure about 4.

Now, if you want to build using Qt Creator, it must be started in a proper environment. Adapt this batch to launch Qt Creator:

ECHO Setting up QGIS DEV ENV

set PYTHONPATH=

set OSGEO4W_ROOT=C:\OSGeo4W
call "%OSGEO4W_ROOT%\bin\o4w_env.bat"

@set QMAKESPEC=win32-msvc2008
@set PATH=%OSGEO4W_ROOT%\bin;%OSGEO4W_ROOT%\apps\qgis-dev\bin;%PATH%

@set INCLUDE=%INCLUDE%;%OSGEO4W_ROOT%\include;%OSGEO4W_ROOT%\apps\qgis-dev\include
@set LIB=%LIB%;%OSGEO4W_ROOT%\lib;%OSGEO4W_ROOT%\apps\qgis-dev\lib

path %OSGEO4W_ROOT%\bin;%SYSTEMROOT%\System32;%SYSTEMROOT%;%SYSTEMROOT%\System32\wbem;C:\Progra~1\Git\bin;C:\Qt\qtcreator-3.0.1\bin;%PATH%

set VS90COMNTOOLS=C:\Program Files\Microsoft Visual Studio 9.0\Common7\Tools\
call "C:\Program Files\Microsoft Visual Studio 9.0\VC\vcvarsall.bat" x86

start "Qt Creator" /B C:\Qt\qtcreator-3.0.1\bin\qtcreator.exe %*

Then, you need to configure a proper kit in Qt Creator.

  1. Go to Options -> Build & Run -> Compilers and check that Microsoft Visual C++ Compiler 9.0 is correctly detected.
  2. Then in Qt Versions tab, add Qt from the OSGeO installation, normally c:\OSGeo4W\bin\qmake.exe
  3. In Debuggers tab, add cdb.exe found in c:\Debugging tools for windows\ 
  4. Finally, check in Kits that it is properly configured.

Building the application

This is what looks like an application project file.

QT += core gui xml
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = hfp
TEMPLATE = app
SOURCES += YOURSOURCES
HEADERS +=YOUR HEADERS
FORMS += YOUR FORMS
RESOURCES += images/images.qrc

win32:CONFIG(Release, Debug|Release) {
 LIBS += -L"C:/OSGeo4W/lib/" -lQtCore4
 LIBS += -L"C:/OSGeo4W/lib/" -lQtGui4
 LIBS += -L"C:/OSGeo4W/lib/" -lQtXml4
 LIBS += -L"C:/OSGeo4W/apps/qgis-dev/lib/" -lqgis_core
 LIBS += -L"C:/OSGeo4W/apps/qgis-dev/lib/" -lqgis_gui
}
else:win32:CONFIG(Debug, Debug|Release) {
 PRE_TARGETDEPS += C:/OSGeo4W/lib/QtCored4.lib
 PRE_TARGETDEPS += C:/OSGeo4W/lib/QtGuid4.lib
 PRE_TARGETDEPS += C:/OSGeo4W/lib/QtXmld4.lib
 LIBS += -L"C:/OSGeo4W/lib/" -lQtCored4
 LIBS += -L"C:/OSGeo4W/lib/" -lQtGuid4
 LIBS += -L"C:/OSGeo4W/lib/" -lQtXmld4
 LIBS += -L"C:/OSGeo4W/apps/qgis-dev/lib/" -lqgis_core
 LIBS += -L"C:/OSGeo4W/apps/qgis-dev/lib/" -lqgis_gui
}
win32:{
 INCLUDEPATH += C:/OSGeo4W/include
 DEPENDPATH += C:/OSGeo4W/include
 INCLUDEPATH += C:/OSGeo4W/apps/qgis-dev/include
 DEPENDPATH += C:/OSGeo4W/apps/qgis-dev/include
 DEFINES += GUI_EXPORT=__declspec(dllimport) CORE_EXPORT=__declspec(dllimport)
}
unix {
 LIBS += -L/usr/local/lib/ -lqgis_core -lqgis_gui
 LIBS += -L/usr/local/lib/qgis/plugins/ -lgdalprovider
 INCLUDEPATH += /usr/local/include/qgis
 DEFINES += GUI_EXPORT= CORE_EXPORT=
}

Remarks

  • GUI_EXPORT and CORE_EXPORT must be set to __declspec(dllimport). I don’t know exactly what it means, but I found out reading this thread, with some hazardous tries. If you don’t set these, you won’t be able to call any variable defined as extern in QGIS (e.g. cursors).
  • Qt release libraries shall not be mixed up with debug config in your project. In other words, use release libs for release mode and debug libs for debug mode.

With this, you should be able to compile your QGIS application in Qt Creator!

You can find some coding examples on github which are a bit old but still useful to start.

Now, to get the whole potential of QGIS libs, you must initialize the QgsApplication in your main window class:

#if defined(Q_WS_WIN)
  QString pluginPath = "c:\\OSGeo4W\\apps\\qgis-dev\\plugins";
  QString prefixPath = "c:\\OSGeo4W\\apps\\qgis-dev\\";
#else
  QString pluginPath = "/usr/local/lib/qgis/plugins/";
  QString prefixPath = "/usr/local";
#endif

  QgsApplication::setPluginPath( pluginPath );
  QgsApplication::setPrefixPath( prefixPath, true);
  QgsApplication::initQgis();

Deploying on windows

Since QGIS is not to be installed on the target computer, the built app will not be able to find the path declared in previous code.
There is probably a better approach, but here is a way to solve this:
Change the path to

  QString pluginPath = "c:\\myapp\\qgis\plugins";
  QString prefixPath = "c:\\myapp\\qgis";

This means you must deploy the app to this exact location: c:\myapp. In this directory, you need to create a qgis folder in which you will copy c:\OSGeo4W\apps\qgis-dev\resources and c:\OSGeo4W\apps\qgis-dev\plugins.

Besides, this you will need to copy some DLLs to be able to run the applications. You might want to use the dependency walker to find which are needed.

The batch file hereafter creates a folder on the building machine that will contain all the needed files in my case (it might be different in your case).

rmdir c:\myapp /Q /S
mkdir c:\myapp
mkdir c:\myapp\iconengines
mkdir c:\myapp\qgis
mkdir c:\myapp\qgis\resources
mkdir c:\myapp\qgis\plugins

copy PATHTOMYAPP\build-myapp-Desktop-Release\release\myapp.exe c:\myapp\
copy c:\OSGeo4W\bin\QtCore4.dll c:\myapp\
copy c:\OSGeo4W\bin\QtGui4.dll c:\myapp\
copy c:\OSGeo4W\bin\QtXml4.dll c:\myapp\
copy c:\OSGeo4W\bin\QtNetwork4.dll c:\myapp\
copy c:\OSGeo4W\bin\QtSvg4.dll c:\myapp\
copy c:\OSGeo4W\bin\QtWebKit4.dll c:\myapp\

copy c:\OSGeo4W\bin\zlib_osgeo.dll c:\myapp\
copy c:\OSGeo4W\bin\msvcr71.dll c:\myapp\
copy c:\OSGeo4W\bin\phonon4.dll c:\myapp\
copy c:\OSGeo4W\bin\proj.dll c:\myapp\
copy c:\OSGeo4W\bin\geos_c.dll c:\myapp\
copy c:\OSGeo4W\bin\gdal110.dll c:\myapp\
copy c:\OSGeo4W\bin\ogdi_32b1.dll c:\myapp\
copy c:\OSGeo4W\bin\libexpat.dll c:\myapp\
copy c:\OSGeo4W\bin\xerces-c_3_1.dll c:\myapp\
copy c:\OSGeo4W\bin\LIBPQ.dll c:\myapp\
copy c:\OSGeo4W\bin\SSLEAY32.dll c:\myapp\
copy c:\OSGeo4W\bin\LIBEAY32.dll c:\myapp\
copy c:\OSGeo4W\bin\krb5_32.dll c:\myapp\
copy c:\OSGeo4W\bin\comerr32.dll c:\myapp\
copy c:\OSGeo4W\bin\k5sprt32.dll c:\myapp\
copy c:\OSGeo4W\bin\gssapi32.dll c:\myapp\
copy c:\OSGeo4W\bin\hdf_fw.dll c:\myapp\
copy c:\OSGeo4W\bin\mfhdf_fw.dll c:\myapp\
copy c:\OSGeo4W\bin\jpeg_osgeo.dll c:\myapp\
copy c:\OSGeo4W\bin\jpeg12_osgeo.dll c:\myapp\
copy c:\OSGeo4W\bin\netcdf.dll c:\myapp\
copy c:\OSGeo4W\bin\geotiff.dll c:\myapp\
copy c:\OSGeo4W\bin\libtiff.dll c:\myapp\
copy c:\OSGeo4W\bin\sqlite3.dll c:\myapp\
copy c:\OSGeo4W\bin\spatialite4.dll c:\myapp\
copy c:\OSGeo4W\bin\freexl.dll c:\myapp\
copy c:\OSGeo4W\bin\iconv.dll c:\myapp\
copy c:\OSGeo4W\bin\libxml2.dll c:\myapp\
copy c:\OSGeo4W\bin\LIBMYSQL.dll c:\myapp\
copy c:\OSGeo4W\bin\hdf5.dll c:\myapp\
copy c:\OSGeo4W\bin\szip.dll c:\myapp\
copy c:\OSGeo4W\bin\libcurl.dll c:\myapp\
copy c:\OSGeo4W\bin\zlib1.dll c:\myapp\
copy c:\OSGeo4W\bin\openjp2.dll c:\myapp\
copy c:\OSGeo4W\bin\spatialindex1.dll c:\myapp\
copy c:\OSGeo4W\bin\qwt5.dll c:\myapp\

copy c:\OSGeo4W\apps\qt4\plugins\iconengines\qsvgicon4.dll c:\myapp\iconengines\

copy C:\Progra~1\Git\bin\libiconv-2.dll c:\myapp\
copy C:\Progra~1\Git\bin\libintl-8.dll c:\myapp\

copy c:\OSGeo4W\apps\qgis-dev\bin\qgis_Core.dll c:\myapp\
copy c:\OSGeo4W\apps\qgis-dev\bin\qgis_gui.dll c:\myapp\
copy c:\OSGeo4W\apps\qgis-dev\bin\msvcp90.dll c:\myapp\

copy c:\windows\system32\msvcp100.dll c:\myapp\
copy c:\windows\system32\msvcr100.dll c:\myapp\

copy C:\OSGeo4W\apps\qgis-dev\resources\* c:\myapp\qgis\resources
copy C:\OSGeo4W\apps\qgis-dev\plugins\* c:\myapp\qgis\plugins

To be able to run the app, on a fresh windows XP, I had to install:

And copy the whole folder c:\myapp from the building machine to the target machine.

It seems that from Vista, the 2005 redistributable package is included. So, no need to install it.

And voilà!


QGIS 2.2 has landed in OSGeo4W

QGIS 2.2 is now available for Windows through OSGeo4W installer. Packages for other systems are being prepared by the package maintainers.

The Windows packages are currently marked experimental, so you have to use the advanced install in OSGeo4W and check the ‘Exp’ radio button on the top to install them.

osgeo4w_qgis22

As release manager Jürgen Fischer announced:

Please test and report problems, so that I can soon promote them to ‘curr’ent.
Once that has happend, I’ll proceed with turning them into standalone
installers.


AGIT 2013: QGIS Cloud - Karten einfach ins Netz

Noch nie war es so einfach individuelle Web Map Services mit ansprechenden Karten, Geodatenbank und Web Client zu erstellen, wie mit QGIS Cloud. Der am 5. Juli an der AGIT 2013 in Salzburg präsentierte Vortrag kann hier herunter geladen werden.

Präsentation

Multithreaded rendering with QGIS

Nowadays, most computers have several processor cores. However, most computer programs are still designed to only use one processing unit. As a convenient and portable way of writing software using all the available processing power, Qt provides the excellent QtConcurrent framework.

In 2010, a Google Summer of Code project examined the suitabilty of using Qt concurrent for rendering the map image in QGIS using several processor cores. Following that approach, each layer renders its image in a separate thread. Once all layer threads are finished, the layer images are composited into one map image and the labels are drawn on top of it. Despite providing good results, that code was unfortunately never merged into the main development branch.

QGIS Enterprise 13.05 will provide the capability of multithreaded rendering. A screencast of the new functionality shows that not only the render time is shorter using multiple cores. More important is to have the possibility to cancel the render progress and the labeling any time, thus achieving a much more responsive user interface when navigating maps.

NTv2 transformations with QGIS

Datum transformations with grid shift files are used in several countries to convert coordinates between different datums. In Switzerland, datum transformation using the NTv2 method is important because of the upcoming conversion between the LV03 system and the new LV95 system. Up to now, doing coordinate transformations with grid shift files was possible in QGIS, but unconvenient.

To use an NTv2 transformation in QGIS, the grid shift file needs to be placed in a directory where proj4 can find it (usually /usr/share/proj on Linux and OSGeo4W\share\proj on Windows). Alternatively, the environment variable PROJ_LIB can be set to point to the directory with the grid shift file(s). Then we have to enable the setting Options->CRS->’Ask for datum transformation when no default is defined’.

The next time we use a coordinate transformation which involves a datum transformation, a dialog shows up and presents the available options.

Now it is possible to select the NTv2 transformation file ‘chenyx06a.gsb’ to convert between LV03 and LV95. It is also possible to select the datum transformation as default to avoid being asked again. Default transformation settings can be changed / added / delted in the options tab (or set during installation by an administrator).

To use an NTv2 based transformation which is not yet in the projection database of QGIS, a new entry has to be added to the datum transformation table in srs.db. If you add a transformation which is widely used in your country, please send the changes back to the project so that those entries can be included by default.

The new datum transformation handling will be available in the upcoming QGIS 2.2 and QGIS Enterprise 13.05. The development has been funded by the Swiss cantons Basel-Landschaft and Solothurn. I also want to thank Fabio Di Pietro, Stefan Ziegler and Frank Warmerdam for answering all my questions about datums, coordinate transformations and proj4.

Just one more day until QGIS 2.2

QGIS 2.2 will be released tomorrow, February 21st. Following the release of 2.0, the QGIS project decided to move to a time-based release plan with releases every four months. This provides a clear framework for developers, translators and documenters which makes it possible to plan ahead and know when tasks have to be finished to be included in a release version.

Similar to the 2.0 release, the project has invested considerable resources to make 2.2 “Valmiera” a successful release. I have already blogged about some of the great new features. Thanks to the project donors and sponsors it was also possible to fund developer time for many important bug fixes.

One of the greatest resources of the QGIS project are its users. One group that deserves our special thanks is the Swiss QGIS User Group. They collect a modest annual membership fee which provides a steady and growing crowd-funding that can be used to positively influence the QGIS project. For example, they invested in bug fixing for 2.0 and they are co-funding work on multi-threaded rendering for QGIS 2.4.

With the rise of new QGIS user groups “QUGs” all around the world, e.g. in Australia, the UK, and the US, I hope these groups will find ways to bring users together and to positively influence the development of QGIS towards the next releases.


Using MetaSearch plugin to search and load (meta)data from your National Georegister

We (mostly Tom Kralidis, Angelos Tzotsos with some additions by me) just released the MetaSearch Catalogue Client plugin for QGIS. The new plugin is an update of the CSWClient plugin from NextGIS. This new MetaSearch plugin makes searching metadata and using the services peanuts! A Catalog Service for the Web (CSW), for example provided by […]

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