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Thu Apr 17 07:55:17 2014

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QGIS Planet

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:

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.

New Mapfish Appserver site with OL3 mobile viewer is online

The city of Winterthur recently launched their new public map portal, based on Mapfish Appserver. Some of the features are outlined in the online help (in German).

Mobile users are redirected to the OL3 Mobile Viewer, which is based on OpenLayers 3 and jQuery Mobile. To have a look at it from your desktop browser follow this link.

In contrary to the desktop version, most of the background layers are delivered as tiles and only topic layers are full size WMS requests. The interesting thing is, that instead of using a tile protocol like WMTS, TMS, etc., an OL3 tiled WMS datasource does multiple WMS requests in a tile scheme. The usual tiling problems (labels, etc.) do not apply for the used raster layers and Varnish serves as cache for on-the-fly generated WMS tiles. In contrary to file based tile caching, much less disk space and more important, no update process is needed.

@PirminKalberer

PDF reports with embedded maps

Printing is always one of the more difficult parts in a web mapping application. There are solutions like the MapFish Print module or the built-in QGIS WYSIWYG PDF printing. But very often users do not want only a map on their print output, but collected information stored in a database with images, etc. - and a matching map. This is the domain of database reporting tools like JasperReports. They provide desktop tools for designing complex reports with texts, graphics, images, tables, etc. and server software for web applications. But how to include a matching map - a map with application parameters like the bounding box or a list of active layers, etc.?

Sourcepole is releasing the missing link between high-quality map printing and database reports, an extension for JasperReports/iReport. This extension makes it easy to embed maps served with the standardized Web Map Service (WMS) protocol.

With this extension installed as plugin for iReport Designer, you have all the reporting features of JapserReports plus a new toolbox component for embedding maps.

This allows you to create multi-page reports with embedded maps using parameters from your web mapping application and complex Jasper expressions.

Source and documentation of the WMS map extension for Jasper Reports is available on Github and binaries as Github downloads

Many thanks to Mika from Panter for implementing the Java stuff and the Canton of Zurich for sponsoring this useful piece of Open Source software.

@PirminKalberer

FOSSGIS 2013: Performance optimised wms services with QGIS server

Performance is usually a top priority for a WMS service. A recent talk at the FOSSGIS (held by Sourcepole) shows what a WMS administrator can do to optimise QGIS server performance. Finally, the performance of QGIS server is compared with UMN mapserver in two production scenarios.

Slides from FOSSGIS 2013 in Rapperswil (in german).

FOSSGIS 2013: Mapfish Appserver

Mapfish Appserver is a platform for building web mapping applications using OGC standards and the Mapfish REST protocol.

Slides from FOSSGIS 2013 in Rapperswil (in german).

QGIS Enterprise – Open Source GIS with LTS Support

Quantum QGIS, a user-friendly and full featured Open Source GIS suite, is used in a wide range of professional enterprise infrastructures. Sourcepole, located in Zurich, Switzerland, now fills the last gap, which has prevented many organizations from the use of QGIS in enterprise infrastructures so far - they offer professional support directly from QGIS core developers. With QGIS Enterprise long term support and maintenance, the customer gets a professionally supported and maintained GIS infrastructure based on QGIS.

QGIS is an official project of the Open Source Geospatial Foundation (OSGeo). It is developed since 2002 by a very active developer community and runs on Linux, Mac OSX, Windows and Android. It provides all features required for a desktop GIS in enterprise use. This includes interfaces to many data formats, extensive analysis functionality, support of main specifications of the Open Geospatial Consortium, numerous styling options, production of ready to print maps and extenddability via Python interface.

The upcoming QGIS Release 2.0 is the basis of the QGIS Enterprise Suite consisting of QGIS Desktop, QGIS Server and QGIS Web Client. These components are maintained by Sourcepole apart from the QGIS community project. Backward compatibility to QGIS 1.8 (Lisboa) plays a major role, because most existing plugins, will not be compatible with the upcoming QGIS community version 2. QGIS Enterprise is currently available for Ubuntu / Debian, RedHat 6, Windows 32bit and Windows 64bit.

Since 2003 Sourcepole is significantly involved in the development of QGIS and supports organizations from 2 to 140,000 employees in the use of QGIS. As an official committer to several OSGeo projects, Sourcepole is able to integrate customer specific extensions into the main software repositories. Improvements of QGIS Enterprise, if possible, will always go back into the QGIS community development.

www.qgisenterprise.com

Faster maps with progressive WMS

The good old OGC WMS has many advantages compared to tiled maps:

  • Continious zoom levels
  • Support for different projections
  • Combination of multiple layers in one request
  • Higher resolutions for printing
  • Better labelling
  • No maintenance needed when updating data

Well known disadvantages are scalability issues for high-traffic sites and a slower response time for complex maps.

The second point can be significantly improved by using a technique known from the progressive JPEG format. Before loading a map with full resolution, a map image with a lower resolution is requested from the server. This results in a better response time, because rendering and transmitting of the low resolution image is significantly faster. The biggest effect on rendering time is in combination with raster layers, but also for vector layers the improvement can be substantial.

High resolution:

Low resolution:

The technique can be easily applied to any WMS using this basic OpenLayers implementation.

There is much room for improvements. The low resolution layer could be tiled, limited to certain zoom levels or having a larger extend for smoother panning.

QGISCloud has this optimization built into the QGIS Web-Client viewer, which helps collecting experience with a wide range of datasets.

QGIS Cloud and Sourcepole are sponsoring Öcher-Safari

QGIS Cloud and Sourcepole are proud to be official sponsors of the team Öcher-Safari, attending the Allgäu-Orient-Rallye. One of the last adventures in the world of cars. Sourcepole serves the team with know how, infrastructure and more. Information about the team and the charity ideas of this event you can find on Öcher-Safari and the official web site of the Allgäu-Orient-Rallye.

installing Postgis 2.0 under Debian wheezy

We’ll be using Postgis2.0 from UbuntuGIS, which has packages for a number of recent Ubuntu releases. Since Ubuntu precise has libc6 2.14 and Debian wheezy only 2.13 we fall back on Ubuntu oneiric for packages, which also has libc6 2.13.

However Postgis 2.0 in UbuntuGIS depends on a lot of llibraries which were in squeeze but live in wheezy under a higher version. Therefore we’ll install a lot of packages from Debian squeeze. Fortunately the libraries are versioned themselves and thus can be installed along the libraries from Debian wheezy.

Let’s go. Add the Debian squeeze sources:

# SRC="deb http://ftp.ch.debian.org/debian/ wheezy main"
# echo "$SRC" >> /etc/apt/sources.list

We’ll also add the security source, in case Debian releases a security update.

# SRC="deb http://ftp.ch.debian.org/debian/ wheezy main"
# echo "$SRC" >> /etc/apt/sources.list

You may want to replace ftp.ch.debian.org by a debian mirror nearer to you.

Now add the UbuntuGIS sources:

# SRC="deb http://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu oneiric main"
# echo "$SRC" > /etc/apt/sources.list.d/ubuntugis.list

Now update and try to install postgis:

# apt-get update
# apt-get install postgresql-9.1-postgis

Create your database:

# sudo su
# su - postgres
$ psql postgres
postgres=# CREATE DATABASE your_db OWNER your_preferred_user:

Now add the postgis features to that database:

$ psql -d your_db -f /usr/share/postgresql/9.1/contrib/postgis-2.0/
$ psql -d your_db -f /usr/share/postgresql/9.1/contrib/postgis-2.0/spatial_ref_sys.sql

That should be it. Let’s hope it works.

A final warning: you are mixing multiple distributions here. This can lead to problems. Due to version conflicts upgrading packages can become very difficult.

Tomáš Pospíšek tpo_hp@sourcepole.ch

Howto shrink a remote root ext3 filesystem on Debian wheezy

This howto describes how to resize a root ext3 filesystem on a remote Debian wheezy server.

This howto is not an original work but only an update of an older howto by Stefan @ https://thunked.org/. This version is specifically adapted to a server running Debian wheezy.

DISCLAIMER:

THERE IS A DECENT CHANCE THAT IF YOU FUCK THIS UP YOUR
REMOTE SYSTEM SIMPLY WONT BOOT AT ALL.  I URGE YOU TO TEST
THIS LOCALLY BEFORE USING THIS METHOD ON A PRODUCTION
SYSTEM. ESPECIALLY IF YOUR SYSTEM IS NOT DEBIAN WHEEZY,
SINCE THAT'S THE ONLY ONE I HAVE TESTED.

THE QUICK WAY:

If you don't want to read the whole thing you can only
execute the commands I run and probably skip the
explanations.

I’ve only done this on Debian Wheezy. If you’re using another distro the initrd layout and init scripts may be a bit different. However, I suspect it looks very similar on almost every distro out there. On Debian my root partition is an ext3 partition.

The general idea is pretty simple: you can’t shrink a mounted partition and it’s impossible to unmount or replace your root partition in a live system, so we have to resize the partition before it is mounted. What we’ll do to accomplish this is change the initrd image to make the init scripts resize the root partition before mounting it. This is by far the most flexible and easy method to resize your root partition I could think of. Most suggestions I found on google required you to create separate OS on a new root partition and boot into that, but I did not have any space to create a new root partition on my remote machine.

Unpacking the initrd image is fairly straight forward:

$ mkdir ~/initrd; cd ~/initrd
$ gunzip -c /boot/initrd.img-3.2.0-3-amd64 | cpio -i --make-directories
62631 blocks
$ ls -l
total 40
drwxr-xr-x 2 root root 4096 Sep 11 20:23 bin
drwxr-xr-x 3 root root 4096 Sep 11 20:23 conf
drwxr-xr-x 6 root root 4096 Sep 11 20:23 etc
-rwxr-xr-x 1 root root 6797 Sep 11 20:23 init
drwxr-xr-x 7 root root 4096 Sep 11 20:23 lib
drwxr-xr-x 2 root root 4096 Sep 11 20:23 lib64
drwxr-xr-x 2 root root 4096 Sep 11 20:23 run
drwxr-xr-x 2 root root 4096 Sep 11 20:23 sbin
drwxr-xr-x 6 root root 4096 Sep 11 20:23 scripts

First, we have to copy all the programs we need to resize our partition onto the initial ram disk. For my ext3 file system I need e2fsck and resize2fs. The programs are depending on a few libraries, so you’ll need to copy those to the new initrd image too. Libraries can also depend on other libraries, make sure you recursively check dependencies until you don’t have any missing dependencies anymore.

$ ldd /sbin/e2fsck
    linux-vdso.so.1 =>  (0x00007fff3594c000)
    libext2fs.so.2 => /lib/x86_64-linux-gnu/libext2fs.so.2 (0x00007f7cdddd5000)
    libcom_err.so.2 => /lib/x86_64-linux-gnu/libcom_err.so.2 (0x00007f7cddbd1000)
    libblkid.so.1 => /lib/x86_64-linux-gnu/libblkid.so.1 (0x00007f7cdd9a9000)
    libuuid.so.1 => /lib/x86_64-linux-gnu/libuuid.so.1 (0x00007f7cdd7a4000)
    libe2p.so.2 => /lib/x86_64-linux-gnu/libe2p.so.2 (0x00007f7cdd59c000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f7cdd214000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f7cdcff8000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f7cde01e000)
$ ldd /sbin/resize2fs
    linux-vdso.so.1 =>  (0x00007fffa216a000)
    libe2p.so.2 => /lib/x86_64-linux-gnu/libe2p.so.2 (0x00007fa01f7a2000)
    libext2fs.so.2 => /lib/x86_64-linux-gnu/libext2fs.so.2 (0x00007fa01f55f000)
    libcom_err.so.2 => /lib/x86_64-linux-gnu/libcom_err.so.2 (0x00007fa01f35a000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fa01efd3000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fa01edb7000)
    /lib64/ld-linux-x86-64.so.2 (0x00007fa01f9b0000)

We only copy the libraries that are not yet present in the initramfs. Fortunately in our case there are no recursive dependencies of those libraries.

$ for i in libext2fs.so.2.4 libcom_err.so.2.1 libe2p.so.2.3; do \
     cp -i /lib/x86_64-linux-gnu/$i lib/x86_64-linux-gnu/; \
  done
$ cd lib/x86_64-linux-gnu/
$ ln -s libcom_err.so.2.1 libcom_err.so.2
$ ln -s libext2fs.so.2.4 libext2fs.so.2
$ ln -s libe2p.so.2.3 libe2p.so.2
$ cd ~/initrd/

$ cp /sbin/e2fsck ~/initrd/bin/
$ cp /sbin/resize2fs ~/initrd/bin/

Next, we need to edit the init script. Debian uses busybox in its initrd image so the init script will be interpreted by a bourne shell. If you look through the init script file you’ll find the moment where the script mounts the root file system:

$ cat scripts/local
...
    # FIXME This has no error checking
    # Mount root
    if [ "${FSTYPE}" != "unknown" ]; then
            mount ${roflag} -t ${FSTYPE} ${ROOTFLAGS} ${ROOT} ${rootmnt}
    else
            mount ${roflag} ${ROOTFLAGS} ${ROOT} ${rootmnt}
    fi
...

Simply add in the commands to resize the file system right before the the file system is mounted. Resize2fs in Debian does not want to resize the file system before it is forcefully checked. It may be wise to add the -p or -y flag to e2fsck. -y will answer yes to all questions, this could prevent a hung system but may cause more damage to your files or filesystem. The -p flag will only automatically answer yes to safe operations. resize2fs takes two parameters, the first is the block device that has the ext2 or ext3 file system and the second is the new size you want to give it. By default the size is in blocks, but you can append a unit to change that. ‘K’ for kilobytes, ‘M’ for megabytes, ‘G’ for gigabytes and ‘T’ for terabytes. If you don’t specify a size, it will enlarge the file system to the total size of the partition or logical volume. After adding the commands the init script will look something like this:

    #RESIZEROOTFS MODIFIED!!! DONT RUN MORE THAN ONCE
    _log_msg "Starting e2fsck"
    /bin/e2fsck -p -f -C 0 /dev/sda4 || true
    _log_msg "Starting resize2fs"
    /bin/resize2fs /dev/sda4 100G || true

    # FIXME This has no error checking
    # Mount root
    if [ "${FSTYPE}" != "unknown" ]; then
            mount ${roflag} -t ${FSTYPE} ${ROOTFLAGS} ${ROOT} ${rootmnt}
    else
            mount ${roflag} ${ROOTFLAGS} ${ROOT} ${rootmnt}
    fi

If you have access to the system’s console, you might want to add a “-C 0” to e2fsck’s parameters. That will show you the progress of the fscheck.

There’s one last thing we have to do before re-packing the initrd image. e2fsck and resize2fs will fail if there is no /etc/mtab file available so we’ll have to make sure /etc/mtab exists.

$ touch ~/initrd/etc/mtab
$ cd ~/initrd/
$ find ./ | cpio -H newc -o > /tmp/initrd.cpio
64097 blocks
$ gzip -c /tmp/initrd.cpio > /boot/initrd-resize.img

And lastly, we need to add a new default boot option in grub. In Debian grub’s configuration file is constructed from various bits under /etc/grub.d. The resulting total configuration file is put under /boot/grub/grub.cfg. Open up the grub.cfg file in your favorite text editor and look for the default entry. It’s usually the first one, but may vary. Add a copy of the original entry to /etc/grub.d/40_custom and change the initrd image to the one we just created.

$ cat /etc/grub.d/40_custom
#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.

menuentry 'resize' --class debian --class gnu-linux --class gnu --class os {
        insmod gzio
        insmod part_gpt
        insmod ext2
        set root='(hd0,gpt1)'
        search --no-floppy --fs-uuid --set=root 0aa8bc27-17e3-4ae2-a9cf-497ab444970b
        echo    'Loading Linux 3.2.0-3-amd64 ...'
        linux   /vmlinuz-3.2.0-3-amd64 root=UUID=660f79dc-c152-4e15-ad61-7075b42de609 ro  quiet
        echo    'Loading initial ramdisk ...'
        initrd  /initrd-resize.img
}

Now make sure that it’s this entry that will be booted into by default. Set GRUB_DEFAULT in /etc/default/grub to the name of the entry you’ve just created:

$ cat /etc/default/grub
# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
# info -f grub -n 'Simple configuration'

#GRUB_DEFAULT=0
GRUB_DEFAULT="resize"
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet"
GRUB_CMDLINE_LINUX=""
...

Finally, you can reboot the system. When it comes back online (if it comes back grin) your file system will be resized. Be aware that e2fsck and resizefs take a long time on big disks. On my system the two took 2 hours for a 1.5T filesystem. Thus don’t prematurely reboot your system if it doesn’t come up again quickly.

Don’t forget to remove the new grub entry, so your file system doesn’t get resized every time you boot.

Original howto at https://thunked.org/general/howto-shrink-a-remote-root-ext3-filesystem-t96.html

Original howto Written by Stefan @ https://thunked.org/

This version for Debian wheezy by Tomáš Pospíšek

Creating png8 images with QGIS server

For providing maps via WMS over the internet, it is important to generate image files with a small size. Because normally, most of the perceived WMS delay comes from transfering large images files over the internet (and not from map rendering itself). Therefore, QGIS server supports the conversion of png24 and png32 images into png8, therefore generating a file with only 1/3 resp. 1/4 of the original size (but with lower quality). However, until recently, QGIS server was using the default algorithm from the Qt library for conversion to png8, resulting in very ugly png8 images if used with a transparent background and sometimes with shifted colors. Therefore, I decided to implement a better conversion algorithm: the median cut algorithm, which was first described by Heckbert in 1982 ( Paul S. Heckbert, Color Image Quantization for Frame Buffer Display. ACM SIGGRAPH ‘82 Proceedings). This algorithm creates color boxes in 4-dimensional colour space and subdivides at the mean of the largest dimension. It stops if the number of boxes equals the requested number of colors (256 in the case of png8 conversion). First tests show the quality of the converted images are quite good for vector maps. So a performant configuration for a webmap means probably to fetch background rasters as jpg and to overlay vectors as png8 with transparent background.

Let’s see with an example what the conversion from png24 to png8 means in terms of image quality. The first file is a png24 image, 590 KB size:

And this one is the conversion to png8, only 190 KB size.

To test the png8 conversion, you need to have the latest QGIS version from git (or a nightly build tomorrow). Then simply replace the FORMAT paramter in the url with ‘&FORMAT=image/png; mode=8bit’.

New configuration options in QGIS server

In QGIS server, it is now possible to selectively exclude layers from WMS publication. These layers will be available only on the desktop and hidden from WMS clients. Similarly, print layouts can be excluded from WMS publication. Of course, these settings are conveniently accessible from the project properties dialog of QGIS (but you need to have a nightly build or a recent compile):

Additionally, attributes per layer can be excluded from WMS or WFS publication in the vector properties dialog:

There is also a new request type called ‘GetProjectSettings’. The output of this request is similar to the GetCapabilities output, but with more details and more specific to QGIS:

  • Initial visibility of layers
  • Information about vector attributes and their edit types
  • Information about layer order and drawing order
  • List of layers published in WFS

These new features have been developed in collaboration and with funding from the city of Uster. More details are available on the QGIS server / webclient wiki page

The state of QGIS Globe

The Region of Umbria, Italy, sponsored 4 days of work to update QGIS Globe for current QGIS versions. Most of the functionality is working again and the globe is now compatible with osgEarth 1.0 up to 1.3. The bad news is, that the globe plugin is not working on Windows with OSGeo4W. It seems that one of the OSGeo4W libraries (GDAL?) is compiled with an incompatible MS compiler version. Christmas holidays are coming…

At least it gives Linux users the possibility to play with the globe using the current development version and do exciting stuff like Oslandia does:

PostGIS 3D demo

Imagine someone would sponsor four weeks of QGIS Globe work!

QGIS - the FOSSGIS week

  • Tuesday, 2012-03-20 11:00: FOSSGIS in Dessau, Germany starts with a workshop for programming QGIS plugins

    A great conference begins, with about 400 people attending presentations and workshops over three days.

  • Tuesday, 2012-03-20 14:42: Changeset c27c89045c: “Add WFS support for QGIS server. Provided by René-Luc D’Hont”

    Wow.

  • Tuesday, 2012-03-20 14.48: QGIS 1.7.4 uploaded to DebianGIS

    Ok, QGIS 1.7.4 is already a few weeks old. But current version on Debian is 1.4.0! This will be a long “new features” list for Debian users. Thanks for your work, Francesco!

  • Tuesday, 2012-03-20 16:00: Marco Bernasocchi demonstrates a fully functional QGIS on a Android tablet.

    GPS support, right click gesture, pinch zooming and offline editing plugin working. Just a few tickets are left for uploading it to Android market. Hopefully we find another great student for this years follow-up GSoC project!

  • Wednesday, 2012-03-21 16.05: Victor Olaya, author of SEXTANTE, announces his work on a QGIS processing framework with toolbox, graphical modeler, batch processing interface, etc.

    Wow!!

  • Wednesday, 2012-03-21 18.30: QGIS and GRASS user meeting at FOSSGIS

    Explaining whats going on in the QGIS code and the QGIS community. Live demonstration of raster resampling branch.

  • Wednesday, 2012-03-21 20.18: Tim announces QGIS 1.8 RC1 for April 9th.

    Test it before the hackfest in Lyon!

  • Thursday, 2012-03-22 08:00: Bad news - three days in a row without any commit from jef!

    What happened? Jürgen forgot to bring his power adapter to Dessau :-(

  • Thursday, 2012-03-22 13:30: FOSSGIS is over

    with well attended QGIS presentations and workshops.

  • Thursday, 2012-03-22 23:37: Changeset 05f7d6baea “fix warnings”, authored by jef-n

    Jürgen is back home again. Phew!

  • Friday, 2012-03-23 10:26: Changeset 585e58179d: Nathan Woodrow merges native MS SQL provider, written by Tamas Szekeres, into master.

    Good news for MS SQL users, but also for Tim: “Finally a way to stop having to use PostGIS all the time…”

What a week for QGIS! Looking forward to more news from the QGIS Hackfest in Lyon.

QGIS - the FOSSGIS week

  • Tuesday, 2012-03-20 11:00: FOSSGIS in Dessau, Germany starts with a workshop for programming QGIS plugins

    A great conference begins, with about 400 people attending presentations and workshops over three days.

  • Tuesday, 2012-03-20 14:42: Changeset c27c89045c: “Add WFS support for QGIS server. Provided by René-Luc D’Hont”

    Wow.

  • Tuesday, 2012-03-20 14.48: QGIS 1.7.4 uploaded to DebianGIS

    Ok, QGIS 1.7.4 is already a few weeks old. But current version on Debian is 1.4.0! This will be a long “new features” list for Debian users. Thanks for your work, Francesco!

  • Tuesday, 2012-03-20 16:00: Marco Bernasocchi demonstrates a fully functional QGIS on a Android tablet.

    GPS support, right click gesture, pinch zooming and offline editing plugin working. Just a few tickets are left for uploading it to Android market. Hopefully we find another great student for this years follow-up GSoC project!

  • Wednesday, 2012-03-21 16.05: Victor Olaya, author of SEXTANTE, announces his work on a QGIS processing framework with toolbox, graphical modeler, batch processing interface, etc.

    Wow!!

  • Wednesday, 2012-03-21 18.30: QGIS and GRASS user meeting at FOSSGIS

    Explaining whats going on in the QGIS code and the QGIS community. Live demonstration of raster resampling branch.

  • Wednesday, 2012-03-21 20.18: Tim announces QGIS 1.8 RC1 for April 9th.

    Test it before the hackfest in Lyon!

  • Thursday, 2012-03-22 08:00: Bad news - three days in a row without any commit from jef!

    What happened? Jürgen forgot to bring his power adapter to Dessau :-(

  • Thursday, 2012-03-22 13:30: FOSSGIS is over

    with well attended QGIS presentations and workshops.

  • Thursday, 2012-03-22 23:37: Changeset 05f7d6baea “fix warnings”, authored by jef-n

    Jürgen is back home again. Phew!

  • Friday, 2012-03-23 10:26: Changeset 585e58179d: Nathan Woodrow merges native MS SQL provider, written by Tamas Szekeres, into master.

    Good news for MS SQL users, but also for Tim: “Finally a way to stop having to use PostGIS all the time…”

What a week for QGIS! Looking forward to more news from the QGIS Hackfest in Lyon.

Shaded relief maps with QGIS

Creating a shaded relief map from digital elevation data is a nice way to create a backround map for web mapping or other GIS work. Thanks to the know-how and the funding from the Swiss Humanitarian Aid Unit, QGIS now has a sophisticated function for relief map generation. The method is described in detail in an paper by Marc-André Bünzli. An important part of the method is the choice of the elevation colors. The QGIS plugin has the possibility to analyse the frequency distribution of the elevation values in the DEM and to propose color changes where significant changes in the histogram occure. It is of course also possible to modify the color scheme, to insert a completely different one in the dialog or to generat a shaded maps without color.

As illustrated below, the relief map is composed by three components modulated onto the final map to give it a more three-dimensional appearance. These intermediate steps are shown here to get a better understanding of the method. In QGIS, the user directly gets the combination as a result.

  • The first component consists of a hillshade from north-west (300 degree) and an elevation color

  • The second component is a hillshade and a gray value depending on the slope angle (darker is steeper). The hillshade angle of this second component differs to the first component by 15% to have better contrast in faces towards the light source. The second component is merged to the relief map with 30% weight.

  • The third component consists of a hillshade from 270 degree and a yellow color in cells facing towards the light source. It is merged to the relief map with 10% weight

And the final relief map looks like this:

Shaded relief maps with QGIS

Creating a shaded relief map from digital elevation data is a nice way to create a backround map for web mapping or other GIS work. Thanks to the know-how and the funding from the Swiss Humanitarian Aid Unit, QGIS now has a sophisticated function for relief map generation. The method is described in detail in an paper by Marc-André Bünzli. An important part of the method is the choice of the elevation colors. The QGIS plugin has the possibility to analyse the frequency distribution of the elevation values in the DEM and to propose color changes where significant changes in the histogram occure. It is of course also possible to modify the color scheme, to insert a completely different one in the dialog or to generat a shaded maps without color.

As illustrated below, the relief map is composed by three components modulated onto the final map to give it a more three-dimensional appearance. These intermediate steps are shown here to get a better understanding of the method. In QGIS, the user directly gets the combination as a result.

  • The first component consists of a hillshade from north-west (300 degree) and an elevation color

  • The second component is a hillshade and a gray value depending on the slope angle (darker is steeper). The hillshade angle of this second component differs to the first component by 15% to have better contrast in faces towards the light source. The second component is merged to the relief map with 30% weight.

  • The third component consists of a hillshade from 270 degree and a yellow color in cells facing towards the light source. It is merged to the relief map with 10% weight

And the final relief map looks like this:

Raster resampling in QGIS

QGIS already offers a lot of possibilities to visualize raster data (contrast enhancement, color map, handling of transparent pixels, …) Last year, Radim Blazek refactored the raster provider interface and added on-the-fly reprojection support for rasters to QGIS. Very cool!

One of the few things currently missing in QGIS raster layer is the possibility to have other resampling types than nearest neighbour. The problem is that rasters appear pixelated when zooming further than the source raster resolution. So for applications like web mapping, it is important to interpolate the pixel colors and to have a broader display scale range for layers. In the last few weeks, I’ve added bilinear and cubic raster resampling to QGIS (thanks to Canton Solothurn for funding these activities!).

A lot of refactoring was necessary in the raster layer code to add resampling in a clean way. Therefore these changes are available in branch ‘raster_resampler’ of the QGIS github clone (git://github.com/mhugent/Quantum-GIS.git). It probably needs a longer period of testing to make sure every feature of the raster layer class still works properly.

The resampling option can be chosen in the raster properties dialog:

And here is the effect for a three band color image.

Nearest neighbour:

Bilinear:

Cubic:

And here for a palletted background map

Nearest neighbour:

Bilinear:

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