I forked the QGIS repo on GitHub a little while ago although one thing that bothered me was that it gave me copies of all the branches that the main QGIS git repo had.  This is understandable as it’s the way it works however I don’t really need all these branches in my forked copy of the repo as I don’t care about them.   I only care the ones I am working on, and I don’t want to see a big list of branches in my git fork that have nothing to do with me.

So the next question was how do I delete all the branches on the remote repo at GitHub. Well you would normally do:

git push origin :branch_name

although doing that by hand for each branch is, well, a pain in the butt! After a chat with a guy (strk) on the #qgis IRC channel who is more skilled at bash then me (I’m still a Linux noob) he came up with this:

git branch -r | grep origin/ | grep -v master | grep -v HEAD| cut -d/ -f2 | while read line; do git push origin :$line; done;

Very handy.

So if you have not already guessed from my increasing post about QGIS. I really like it as a GIS system but with all systems it comes with its shortcomings. (Nothing that can’t be fixed of course)

Here is my little wishlist of a few things I would love to see in QGIS.

Multipule map canvases. (ArcGIS, MapInfo)

I was thinking more like ArcGIS data frames vs something like what MapInfo has (multiple windows).  I think the multi window system can add confusion for people new to GIS, plus I hate having to window manage.

SQL like interface. (MapInfo)

This is something that I really like from MapInfo.  It adds a lot of power to the application being able to spatially join two tables that don’t share a command link column and get back a new layer.  Adding this to QGIS could be a pretty big task, although a very rewarding one IMO.  

Now there is some credit in saying “well you can just import your data into PostGIS and use that”, however that is not always a option and I think having a layer above that can query any open layer would be very very powerful.

These are just two of the main things that I would like to see, I’ll update the post if I can think of anymore.

Of course being open source I can write the features myself but C++ is still a bit over my head at the moment.

I would love to see what other peoples thoughts, or mini wishlists, are.  So if you are willing, drop a comment and let me know.

EDIT:  If you are having trouble opening MS SQL 2008 in QGIS I will have a blog post coming explaining how to correct it. Or you can read the comments between TheGeoist and I below which will have the answer.

Just a quick tip.

Thanks to GDAL/OGR 1.8 QGIS can now open MS SQL Server 2008 spatial tables via the OGR MSSQLSpatial driver.

First you must be running a version of QGIS that is using GDAL/OGR 1.8.  Opening the QGIS about page will tell you if it is supported.

Need version 1.8 or higher

As I am writing this on my Ubuntu install I only have version 1.6.3 but the latest dev version of QGIS (upcoming 1.7 release) for Windows in the OSGeo4W installer is complied with version 1.8.

Now open the python console in QGIS and type the following:

uri = "MSSQL:server={serverName};database={databaseName};tables={tableName};trusted_connection=yes"
qgis.utils.iface.addVectorLayer(uri,'{yourLayerNameHere}','ogr')

Replacing {serverName} with your server name, if installed on your local machine you can use localhost; {databaseName} with the name of the database with the tables;{tableName} with the table to open; {yourLayerNameHere} with the name you would like the layer to have in the map legend.

After that you should see your MS SQL Spatial table displayed in QGIS, with editing support.

At the moment there is no nice interface in QGIS to open MS SQL tables like there is for PostGIS, although that might be a good plugin project for someone to work on.

Note:  This post is about getting ecw and mrsid support working in the trunk (qgis-dev) version of QGIS which is installed with the OSGeo4W installer.  Non-dev versions seem to work fine following this method: http://www.qgis.org/wiki/OSGeo4wSetup#Installing_support_for_raster__.2A.ECW_.28ERMapper.29_and_.2A.sid_.28MrSid.29_formats

Getting ECW and MrSID support into QGIS can be a real pain in the butt when you first try; but once you know how it’s easy.

If you try to open a ecw file in QGIS you will get this nice little error message:

What?  I thought QGIS supported ECW files!

Turns out it does, but the team are not able to ship the required libs with the program due to licensing restrictions by ERDAS.   Luckily adding support is not “too” hard.

1. First head over to http://www.erdas.com/products/ERDASECWJPEG2000SDK/Downloads.aspx
2. Click Download Now for the ERDAS ECW/JP2 SDK Desktop Read-Only, Version 4.1 libs,
3. Fill out a bit of registration details and click though all the pages (this is the most painful process I have ever had to go though to get some libs for a program, ERDAS should be ashamed that it is such an effort.)
4. Once you have download ECWJP2SDKSetup_RO_20100920.exe; install it.
5. Copy all the files from C:\Program Files\ERDAS\ERDAS ECW JPEG2000 Read SDK\bin\vc90\win32 into the bin folder of your OSGeo4W install (default is C:\OSGeo4W\bin)
   You can open the OSgeo4W shell and run: copy “C:\Program Files\ERDAS\ERDAS ECW JPEG2000 Read SDK\bin\vc90\win32\*.dll” %OSGEO4W_ROOT%\bin to do the same thing.
6. Launch osgeo4w-setup.exe, the installer that you used to install qgis-dev,  and select  gdal-ecw, gdal17-ecw and gdal-mrsid, gdal17-sid under the libs section. Let it install the needed libs and any dependencies.
7. Open %OSGEO4W_ROOT%\bin and search for qgis-dev.bat; open it with a text editor and add the following line:
   set GDAL_DRIVER_PATH=”%OSGEO4W_ROOT%”\bin\gdalplugins\1.8
   I always insert it just after  SET OSGEO4W_ROOT=
8. Launch qgis-dev.bat
9. Open a ecw

ECW file opened in QGIS

I have tested this on a couple of machines now but as always

with no guarantee that it will work on yours :)  (Although it should)

The other day I was trying to get the total length of the some selected lines in QGIS. In MapInfo I would just do

Select Sum(ObjectLen(obj,”m”)) from Selection

however QGIS doesn’t have the ability (yet..) to run SQL queries like this, but you can do it via python.

The following is a little python snippet that will get the total length of the selected objects. (You will need to have shapely installed to use)

from shapely.wkb import loads
def getLength():
    layer = qgis.utils.iface.mapCanvas().currentLayer()
    total = 0
    for feature in layer.selectedFeatures():
        geom = feature.geometry()
        wkb = geom.asWkb()
        line = loads(wkb)
        total = total + line.length
    return total

print getLength()

EDIT:Or as Peter asked in the comments, yes you can just call length on the geometry:

def getLength():
    layer = qgis.utils.iface.mapCanvas().currentLayer()
    total = 0
    for feature in layer.selectedFeatures():
        geom = feature.geometry()
        total = total + geom.length()
    return total

print getLength()

Just copy and past that into your QGIS python console and call getLength() when ever you need the total length.

Note: I have found the QgsGeometry .legnth() function to be unstable in the past and it has crashed my QGIS instance. Just test it first, if not you can always use the shapely method.

Just a quick one.

This afternoon I was having a go at getting our work MapInfo layers to look the same in QGIS as they do in MapInfo.  I wanted to do this; 1) So I can print maps from both systems for people and they are a consistent style 2) Would rather use QGIS for every day map work.  3) To see what they compare like.    I think it came out pretty good, apart from few symbols that I didn’t get time to finish.

MapInfo vs QGIS

Note that MapInfo has anti-aliasing and transparency  turned off, as it makes MapInfo very slow and render any output as bitmaps rather than vectors (poor).  Where as QGIS is using both, as it doesn’t suffer from the same problems.

EDIT: To be fair here is both with the best settings turned on.  They are pretty much the same, which is a good thing.

A couple of days I found a pretty cool open source project for visualizing the history of version controlled code.  The project is called Gource and can be found here: http://code.google.com/p/gource/ On the videos wiki page there are a few videos of other projects that have used gource to generate cool videos of their commit history so I thought I should make one for QGIS.

After downloading and building the latest source for Gource and fetching the current trunk of QGIS following these instructions: http://spatialgalaxy.net/2010/12/27/contributing-to-qgis-using-git/ I ran the following in my terminal on my Ubuntu machine, with my current directory being the download git repo from the above instructions:

  gource --title "Quantum GIS" --logo images\icons\qgis-icon.png \
  --hide filenames --date-format "%d, %B %Y" --seconds-per-day 0.15 \
  --highlight-all-users --auto-skip-seconds 0.5 --file-idle-time 0 --max-files 999999999 \
  --multi-sampling --stop-at-end --elasticity 0.1 -b 000000 \
  --disable-progress --user-friction .2 --output-ppm-stream - | \
  ffmpeg -an -threads 4 -y -b 3000K -vb 8000000 -r 60 -f image2pipe \
  -vcodec ppm -i - -vcodec libx264 -vpre libx264-medium qgis.mp4

Don’t worry I know it looks crazy but it’s really not that bad.  I’ll break it down.

• –title “Quantum GIS” Well, yeah, adds a title to the project.
• –logo images/icons/qgis-icon.png Adds a icon watermark
• –hide filenames This hides the filenames of the files being committed . I hide these because it makes it pretty hard to see.
• –date-format “%d, %B %Y” Formats the date at the top of the video.
• –seconds-per-day 0.15 How many seconds represent a day. The lower this is the fast a day goes by, meaning me commits in less time.
• –highlight-all-users Highlights all the users all the time.
• –auto-skip-seconds 0.5 If there are no commits for this time it will skip to the next commit.
• –file-idle-time 0 How long before the file disappears from the video, 0 means never good for seeing the full file tree.
• –stop-at-end Stops the video at the end of all the commits.
• -b 000000 The background colour, in this case black.
• –output-ppm-stream – Tells gource to output the result ppm stream to STDOUT, which is then piped ( | ) into the ffmpeg

That is a quick overview of some of the gource arguments, running grouce -H in your terminal will print out the full list.  I’m not going to go into the ffmpeg arguments because frankly I don’t understand them very well and video isn’t really my thing.  I’m sure there are ffmpeg experts that would be able to do it better then what I have.

After running the above commands in my terminal window and letting it do its thing, I had a resulting mp4 file which I then uploaded to YouTube.

Below is the video that I uploaded to YouTube, which took about 5 hours due to my very very slow (read 138kb/s) upload speed.  The video is about 8 years of QGIS development in just over 9 minutes.

As it’s a bit hard to see in the video due to the quality, each cluster of files is a directory and the branches show the folder hierarchy.

Direct link to video: http://www.youtube.com/watch?v=-NILKRiMtcU

Happy new year and happy coding