An advantage of using map services like WMS and WMTS is that your styling has been done by someone else. But this can turn into a disadvantage as well in case the colours of your overlay are similar to the colours in your remote base layer. To show this I created an example using the [...]
No words for this one, just pictures! Above: What we are trying to achieve… Above: Our symbol layers Above: The roof colour is data defined A shadow Layer And a highlight layer One other hint – don’t forget to enable symbol levels!
The excitement about the upcoming 2.0 release is growing and to add some fuel to the fires, Mathieu founded the QGIS Flickr Group. Anyone can join and add their maps done with QGIS master.
I’m looking forward to seeing what you have come up with. Please note that this group is meant for maps only (therefore no screenshots of the application please).
De Basisregistratie Topografie (BRT/Top10NL) houdt ongeveer een kilometer na de landsgrens al op. Velen, bijvoorbeeld brandweermensen, hebben behoefte aan meer kaartbeeld over de landsgrens. Die kaartdata is er, en nog kosteloos ook. De Open Street Map (OSM) van de Europese landen is als Shapefiles te downloaden, o.a. via de Duitse GeoFabrik, http://download.geofabrik.de/europe.html. Ze wordt aangeboden in [...]
Sextante is quickly becoming the goto geoprocessing toolbox for me. I’ve been working with Sextante 1.0.8 on QGIS 1.8 and lately I’ve started looking into Sextante 1.1 for QGIS 2. This post highlights some of the main differences between the two versions. I’m sure there are many more hidden gems I have not discovered so far.
One thing you will notice if you have used previous versions of Sextante is that the new version comes with a simplified interface which groups tools into three categories: geoalgorithms, models, and scripts. If you prefer the old style grouping by algorithm source such as GDAL, GRASS, etc. you can switch to the Advanced interface.
Let’s start with the bad news: Models created in 1.0.8 are not compatible with 1.1 since many of the algorithms have been rearranged in new categories and Sextante cannot find them by their old names anymore, e.g.
1.0.8 … ALGORITHM:ftools:fixeddistancebuffer
1.1 … ALGORITHM:qgis:fixeddistancebuffer
The great news is that the modeler has been improved greatly. Model representations now show the flow of input and output data through the model steps much more clearly:
Sextante 1.0.8 modeler
Sextante 1.1 modeler
I also found the new modeler much more stable – no crashes so far. *fingerscrossed*
Another nice new feature is Sextante commander which can be started using the shortcut Ctrl+Alt+M. It’s a quick launch solution for all Sextante algorithms:
At FOSS4G, I’ll be presenting some work I did evaluation OSM using Sextante 1.0.8. I’d love to hear how you are using Sextante.
Today’s post: More print composer overview magic!
Thanks to the “Invert overview” option, we can now chose between highlighting the detail area (left example in the image) or blocking out the surrounding area (right example).
The “Lock layers for map item” option can come in very handy if you want to reduce the number of layers in the overview map while still keeping all layers of interest in the main map.
The dutch PDOK-services plugin is a simple plugin to load some national (PDOK) dataservices. One of the available services is a Web Features Service (WFS), while a very handy service, calling the WFS service to load all roads in the Netherlands shows you the following result: As you can see the blue bar are actually [...]
It seems upgrading to Ubuntu 13.04 breaks a few things in the QGIS build process. Here’s some quick workarounds I’ve found to get it building again.
Firstly, Ubuntu defaults to Qt 5, causing the error:
CMake Error at /usr/share/cmake-2.8/Modules/FindQt4.cmake:1216 (message):
Found unsuitable Qt version "5.0.1" from /usr/bin/qmake, this code requires Qt 4.x
This can be fixed by switching the system default back to Qt 4, so that qmake refers to the Qt 4 version. The “qt4-default” package handles this switch for you, so just run:
sudo apt-get install qt4-default
Update: A better solution was found by Pierre and Pvanb and is described here. Basically it involves changing the QMAKE_EXECUTABLE option from /usr/bin/qmake to /usr/bin/qmake-qt4.
Next, I was getting the error:
make[2]: *** No rule to make target `/usr/lib/libpython2.7.so', needed by `output/lib/libqgispython.so.1.9.0'. Stop.
I’m not sure if this is the correct solution, but setting up some links and re-running ldconfig gets around this:
sudo ln -sf /usr/lib/x86_64-linux-gnu/libpython2.7.so.1 /usr/lib/libpython2.7.so.1 sudo ln -sf /usr/lib/x86_64-linux-gnu/libpython2.7.so /usr/lib/libpython2.7.so sudo ldconfig
Update: a better solution is to change the PYTHON_LIBRARY option from /usr/lib/libpython2.7.so to /usr/lib/x86_64-linux-gnu/libpython2.7.so
These two changes were enough to get QGIS building again. If you’ve got a better solution for these errors, let me know…
Here’s a cool trick which you can do in QGIS 2.0. It builds on two new features introduced in version 2.0 – atlas prints and html labels.
Atlas prints (previously available as a plugin, now integrated into QGIS core) were developed by Oslandia, and allow you to create data driven map layouts from a specified coverage layer. You can read more about them here.
Another new feature in QGIS 2.0 is the ability to render composer labels as html (courtesy of Olivier Dalang). This allows all kinds of fantastic effects, such as formatting text in the middle of a label (using <b>, <i>, and <font> tags) or creating labels which contain HTML tables. You can even use CSS stylesheets and rules to format the HTML! I’ve been told JavaScript also works inside the labels, but I’ve yet to try this out.
You can combine these two new features for some great tricks. Let’s say we’d like to create a set of maps of local councils, and we want each map to have a watermarked logo of the council on it. For this example I’ve created a basic basemap of Victorian councils, and I’ve downloaded all the council logos (in a variety of formats) to a local folder. Next, I’ll add an extra column to the council layer containing the name of the logo image:
Adding a logo column to the table
Then, we’ll throw together a simple composition containing the map and set it up as an atlas print:
Generating an atlas
Now for the fun bit. I’ll add a label item to the composer, set it to “Render as HTML”, and insert some specially-crafted html:
The magic HTML label…
For copy/paste purposes here’s the label contents again:
<style>
* {margin: 0px; padding: 0px}
</style>
<img src="file:///home/nyall/GIS/council_logos/[% "logo" %]"
style="width: auto; height: 100%; display: block; margin: 0px 0px 0px auto;" />
There’s a couple of things to note here. First, the magic happens in the image’s src attribute (“file:///home/nyall/GIS/council_logos/[% "logo" %]“). When the composer is exported, QGIS will replace the [% "logo" %] part with the contents of the logo field for each row in the councils table. This means the image source will then point to the local copy of the council’s logo, eg “file:///home/nyall/GIS/council_logos/glen_eira.jpg” for the first row.
Secondly, I’ve styled the image with the css:
width: auto; height: 100%; display: block;
This allows the image to resize to 100% of the height of the label while maintaining its correct aspect ratio. I’ve also added the rule
margin: 0px 0px 0px auto;
to force the image to right align within the html label. This ensures that all the watermarked logos will appear in a consistent size and position for each map.
Lastly, I’ll remove the label’s frame and background by unchecking these options, then set its transparency to 80% under the new “Rendering” section:
Yet another new feature in QGIS 2.0…
Ok, we’re all done. Now, when I select Composer -> “Export as Image”, we’ll get a lovely set of council maps complete with watermarked council logo!
A watermarked atlas!
There we go — all ready for print, with no manipulation in external programs required at all!
Here’s a kicker — the linked images don’t need to be local. That means you can even piggy-back off an existing web service to generate an image on the fly! Let’s say you were asked to add QR codes to your maps to link directly to the council website. All it takes is adding a new column to the table, then modifying the image src to read:
src="http://qrfree.kaywa.com/?l=1&s=8&d=[% "url" %]"
Now when we export the maps we’ll also get a QR image generated on the fly and inserted into the layout!
Complete with dynamically generated QR code!
Combining HTML labels and atlas prints in this way is extremely powerful. This example is just touching the tip of the iceberg – I’m keen to see what the community can do with this when QGIS 2.0 is released!
Advanced Python field calculator is one of the numerous tools in Sextante for QGIS. It’s extremely powerful but it doesn’t use the syntax of QGIS’ default field calculator (the one you can access via attribute table). Therefore, here comes a short introduction:
If you want to reproduce this example, I used a dataset of town areas from the new open government data site of Lower Austria.
The upper half of the Advanced Python field calculator is rather self-explanatory but the lower half is where it gets interesting: Code in the global expression section will be executed only once before the calculator starts iterating through all the features of the input layer. Therefore, this is the correct place to import necessary modules or to calculate variables that will be used in subsequent calculations. Code in the formula section will be evaluated for each feature in the input layer. As shown in the following example, this is where we can calculate new values, e.g. the area of the polygons in km²:
As you can see, the feature geometry can be accessed using $geom.
If you want to access an existing attribute, that’s possible using <attribute_name>.
Anyway, this is the resulting layer’s attribute table including the new areaKM2 field:
Thanks to Victor for pointing me to the documentation of FieldPyculator which Advanced Python field calculator is based on.
View here on youtube: https://www.youtube.com/watch?v=rnqRAOvuJEU
View here on youtube: https://www.youtube.com/watch?v=oOhbbEkl4Kg
Continuing on from part 1, another feature I’ve recently pushed to QGIS is the ability to control the hue, saturation and colour of a raster layer. This builds off the excellent work done by Alexander Bruy (who added brightness and contrast controls for raster layers), and it’s another step in my ongoing quest to cut down the amount of map design tweaking required outside of QGIS. Let’s step through these new features and see what will be available when version 2.0 is released in June…
First up is the ability to tweak the saturation of a layer. Saturation basically refers to the intensity of a colour, with low saturation resulting in a more washed out, greyer image, and high saturation resulting in more vibrant and colourful images. Here’s a WMS layer showing an aerial view of Victoria at its driest, least appealing and most bushfire ready state:
Raster layer before saturation controls…
Let’s tweak the saturation a bit to see if we can make it more appealing. In the Style tab under raster layer properties, you’ll see a new “Saturation and hue” section. For this layer I’ll bump the saturation up from its default value of zero:
Saturation settings
Which results in something like this:
… and after increasing the saturation!
Ah, much better. This actually looks like somewhere I’d like to live. A bit over-the-top perhaps, but it IS handy to make quick adjustments to raster colours in this way without the need for any external programs.
How about turning an image grayscale? I regularly have to do this with street directory basemaps, and until now couldn’t find a satisfactory way of doing this in QGIS. Previously I’ve tried using various command line utilities, but never found one which could turn an image grayscale without losing embedded georeferencing tags. (I did manage to achieve it once in QGIS using a convoluted approach involving the raster calculator and some other steps I’ve thankfully forgotten.)
But now, you can forget about all that frustration and quickly turn a raster grayscale by using a control right inside the layer properties! You even get a choice of desaturation methods, including lightness, luminosity or average. Best part about this is you can then right click on the layer to save the altered version out to a full-resolution georeferenced image.
Street map in grayscale… woohoo!
Lastly, there’s the colourise option. As expected, this behaves in a similar fashion to the colourise tools in GIMP and Photoshop. It allows you to tint a layer to a specified colour. Let’s take a WMS layer of Melbourne, tweak the brightness and contrast, and colourise it blue…
Tweaking the colourize settings
… and the end result wouldn’t be out of place in Ingress or some mid 90′s conspiracy flick!
Colorized WMS layer
These changes are just a tiny, tiny part of what QGIS 2.0 has to offer. It’s looking to be a sensational release and I can’t wait for final version in June!
The latest version of Print composer features new
Rulers are a well-known feature in graphics programs such as Gimp and Photoshop. Now you can also find them in QGIS Print Composer. Click onto the ruler, hold the mouse key down and move the cursor to position guide lines for map feature alignment.
Of course, there’s also the handy “Snap to grid” functionality.
This fifth part in my series on QGIS 2.0 Print Composer presents
There are numerous different options for map grids in the new composer but a picture is worth a thousand words:
The upper-left map features a zebra frame style and coordinate labels aligned horizontally and vertically.
The upper-right map shows a normal frame with labels written inside the frame instead of outside. This grid shows an additional offset.
The lower-left map has no frame but customized, colored and dashed grid lines.
Finally, the lower-right map shows a cross grid with default horizontal coordinate labels.
I’ve just pushed my first major contribution to QGIS — the ability to set the compositing mode for a layer. Compositing is a technique widely used by cartographers and graphic artists to fine tune how layers are blended together, and it allows for some spectacular results! Until now, the only way to get these effects would be to export a map to a separate editor like Photoshop or GIMP and playing with the layer modes there. But with QGIS 2.0, blending can be controlled via a simple drop down menu for both raster and vector layers:
Woohoo… blending modes in QGIS!
So what makes this so great? Well, in previous versions the only option for compositing layers in QGIS was by setting a layer’s opacity. This approach has some limitations. Let’s say you want to overlay two raster layers – a basemap layer and a heatmap. You could place the heatmap layer over the basemap and set its transparency at 50% so that the basemap shows through, but then both the basemap and heatmap layers will be partially faded out:
Overlaying layers by altering transparency – see how both the heatmap and basemap are partially faded
With QGIS 2.0, you’ll be able to use the “multiply” blend mode to overlay these layers. This means both the heatmap and underlying basemap will be shown with full intensity:
Overlaying rasters with “multiply” blend mode – both layers are shown in their full intensity!
Ok… perhaps that’s not the prettiest example, but it is something I have to do a lot in my job. Until now it’s only been possible by exporting the map to GIMP or Photoshop/Illustrator and setting the blend modes there. That’s always fiddly, time consuming and generally frustrating all round. Much easier to just change it with a dropdown within QGIS itself.
Let’s move on to some more impressive example. First, here’s a terrain map using a combination of a landcover thematic with ‘overlay’ blending and a hillshade set to ‘multiply‘ blending. The graticule lines are also set to overlay – note how they aren’t visible over the lighter water areas and brighter hillshade regions.
Hill shading with advanced compositing… Hal Shelton would be proud!
Ok, that’s nice, but let’s try something a little different. Using a combination of darken, screen, hard light and overlay:
Live Stamen-style watercolors within QGIS – sweet!
These a just some rough examples — I’m keen to see what results others get using this feature (feel free to post links to your work in the comments).
One final note: I’m really appreciative of the efforts of the QGIS dev team, who’ve been really supportive and helpful while I find my way around the QGIS codebase. A big thank you has to go to Nathan Woodrow for taking the time to review this commit and answering all the questions I’ve had!
Today’s spotlight is on a feature which you’ll really love if you have to arrange a little more text on a print layout:
Regular labels are limited to one font, size and color. With the new “Render as HTML” option, you gain flexibility to use HTML tags to style your text by adding headers, lists and even images (note the QGIS logo I added by pointing to the image online):
After guide lines and multi-column legends, today’s focus is on
Small overview maps are used to help the reader get an idea of where the region displayed on the main map is located. In the new Print Composer, it’s simple to add such overviews: Add the main map as usual. Then add another map object to the composition an go to the “Overview” section. There, you can specify that the second map object should be an overview map for the first one: Just specify “Map 0″ in the dropdown list:
After yesterday’s first post on guide lines & snapping for user-friendly map element arrangement, we’ll have a look at another great new addition:
In the panel on the right, there is a new section called “Columns”. Here we can create multi-column legend layouts by specifying the desired number of columns. Add some spacing too. It will make the result look more balanced.
By default, Print Composer tries to keep all classes of one layer in one column. You can override this behavior – as I did in this example – by ticking “Split Layers”:
Another useful trick is to use text wrapping for long class labels. This option can be found in the legend’s “Main properties” right at the top of the side panel. In this example, I specified wrap on the pipe “|” symbol and inserted this symbol into the longer class names to force a line break:
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