Tag Archives: open

Convert 16bit to 8bit GeoTiff

Note to self: use the following command to scale 16 bit spatial raster data down to 8 bit.

gdal_translate -a_nodata 0 -of GTiff -ot Byte -scale 0 65535 0 255 input.tif 8bit_output.tif

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It’s been a busy conference month: they didn’t rename it Maptember for nothing! Of all the conferences that were held (especially in the UK) I have attended three: the RSPSoc conference in Glasgow; AGI Geocommunity; and FOSS4G. The latter two were both held in Nottingham, re-branded Mappingham during FOSS4G.

These were three very different conferences, at least from my perspective. The RSPSoc conference had approximately 130 delegates, a fair number of whom I knew or recognised. Maybe this is why I felt most comfortable at this conference. The RSPSoc annual conference is very much an academic conference and a key part of the remote sensing calendar. It’s a brilliant opportunity to see what new methods and applications are being developed in the RS sector.

This was my first time at both the AGI GeoCommunity and FOSS4G conferences. To be honest, I wasn’t sure what to expect as my background is much more on the RS side, rather than the GIS side. I didn’t attend all of the events available at these conferences as funds are limited this year, so I only made the final day of the AGI GeoComm and the two main conference days of FOSS4G. I realise that there were loads more to both conferences and wish I could have made everything. For comparison, there must have been a couple of hundred attendees at GeoComm and there were about 850 at FOSS4G.

Some random points I have taken away from the conferences:


  • There were two great keynote speeches given by Stewart Walker and Craig Clark.
  • I chaired a session on behalf of TOPSIG (Technical and Operational Procedures SIG) – there were some great presentations in that session and I’d like to thank all the speakers for their efforts.
  • The ARGUS-IS is a bonkers system – check out (http://www.youtube.com/watch?v=QGxNyaXfJsA) to see what I mean
  • Doreen Boyd presented some very cool work being undertaken at the University of Nottingham on using traffic cameras as data sources for validation work (http://www.mdpi.com/2072-4292/5/5/2200)
  • Glasgow was a lot warmer than I thought it would be!

AGI GeoCommunity

  • Maybe I was expecting more from the level of the talks at this conference or maybe I want to the wrong talks, but having come from the RSPSOc conference (and understanding that the AGI GeoComm was the flagship event in the UK of the GIS community), I was surprised not to be listening to reports about cutting edge developments. The talks were interesting in their own way, but they came across as very generic for what I assumed was going to be a specialist audience.
  • Anne Kemp did a really good job of chairing the day 2 opening session. She got audience members to identify themselves as groups of professionals who have worked in the sector for >20 years, 10-20 years and <10 years. She made the point that these groups should make sure they mix and pass on skills and experience to each other. It was a lot more effective than my description is making out!
  • Peter Batty gave a well timed keynote on Openness at the end of the day in readiness for FOSS4G (http://www.slideshare.net/pmbatty/agi-geocommunity-2013)


  • I was nervous about attending this. I am not a developer. I can script in Python, but to me that is very different to being a software developer. I wondered whether the entire conference would be full of developers talking code rather than something for general users. I was steadied for rapidly getting lost in the detail, but it wasn’t like that at all. It was a totally inspiring experience, especially once I realised that I was brushing shoulders with some of the rock-stars of the FOSS world. The local organising committee did a great job of pulling together people from different (but related) technical backgrounds, cultures and languages and making the conference feeling one of cohesion.
  • The talks were brilliantly structured to take you from discussions of what ‘open’ means to hardcore technical breakdowns.
  • Arnulf Christl is an inspirational speaker and fully deserved to be presented with the Sol Katz Award


The main thing I learnt from all of the conferences – contribute in some way (as a developer, user, speaker, volunteer) and build your community. Collaborative research and development is fun, everyone has something to offer, and more often than not people are intrigued/excited/chuffed by what you say or do.


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Command line shennanigans

The following (and quite a bit of what will come in future on Linux related topics) is summarised from various linux for noobs websites, magazines and blogs. None of it is taken as written, unless quoted, apart from the commands. The main reason for plonking it all on this site is so that I have a reference for when I need certain commands and knowledge on how to get stuff done. It would be great to be corrected if any of this is out of date or if there is a better way to do it.


  • command > file : send command output to a file
  • command 2> file : send the error output from a command to a file
  • command > file 2>&1 : send both command and error output to a file
  • command < file : read inputs to a command from a file
  • command < file.in > file.out : read file contents into a command and save output to a file
  • command >> file : append the results of a command to the end of a file
  • command 2>> file : append error output to the end of a file
  • command | command2 : pipe command output into command2

File manipulation examples

  • sort < /etc/passwd : this is an example of redirecting the command input from a file. It outputs a sorted list of lines in the file /etc/passwd
  • grep typedef /usr/include/* > output.file : this example searches for typedef in all the files in /usr/include and then saves the search results into a file which can be used as input or opened for analysis
  • find / -name COPYING -print 2> output.txt : this command example searches through the file system (starting at root, /) to find files named COPYING and outputs the error messages into output.txt. The errors should be access denied type messages in this case. Use nano output.txt (or the editor of your choice) to view the contents of that file. To ignore the error messages send them to /dev/null

History commands

  • history 5 : shows the last 5 commands
  • history > hist.txt : outputs the full command history into hist.txt
  • !! : repeat last command
  • !command : repeat last instance of a specific command
  • !23 : repeat command 23 (as found in hist.txt)
  • !! | command : repeat the last command and pipe it into command
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This is a really cool bit of mind mapping software. See http://people.gnome.org/~dscorgie/labyrinth.html and http://code.google.com/p/labyrinth/ for more details. It allows you to create mindmaps that include traditional text items, but also with the added bonus of allowing you to sketch and upload images.

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One of the best adverts out there for the use of open source geospatial technologies is the OSGeo Live DVD (http://live.osgeo.org/en/overview/overview.html). It contains working examples of so much software that you almost don’t know where to start. the documentation is clear and precise and there are all sorts of tutorials on the web explaining how to get started with the distro.

If you haven’t worked with this before I recommend you check it out, but be aware that the download is huge and it can be a bit slow if you run it in a virtual machine.

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