About a week ago I announced the initial release of my new small utility “dutree”. For an explanation of the purpose of the program, see the previous post. It was still missing an important feature that I wanted, namely gauges displaying the relative disk usage for the listed entries. This feature has now been implemented, and it is available in the new version 0.1.1. I also added an option for specifying a maximum depth for the listed entries. This makes it a lot easier to get an overview if there are many subdirectories and files. Click here to download the dutree source code.
Improved “dutree” Released
August 15th, 2008Dandelion Leaves are the Best
August 10th, 2008At least it is the favourite greens of my bearded dragon (pogona vitticeps). She is called Gunnar, although that is a boys name — you can’t determine the sex before half a year or so after hatching, and even then it’s not obvious. Gunnar is around 4½ years of age now, and I’m not entirely sure whether that is young or old for a bearded dragon. I’ve heard anything between 5 and 10 years is normal, depending on their conditions and if bred or not. She doesn’t look and act old yet, though. 
I just thought this was a funny little photo series, so I wanted to share it. Of course bearded dragons are not herbivores, and indeed the primary feed is crickets, grasshoppers, and a couple of mealworms once in a while. Click on the pictures below for larger versions.
New Utility “dutree” Released
August 6th, 2008
I would like to announce that I have released a new simple command line utility that I call “dutree”. As the name suggests, it’s an alternative to du (a tool for summarizing disk usage), but it displays the results in a tree. This is not a big step up, I know, but I plan to add a column with gauges visually indicating the size of the entries compared to the total. I personally find that a much better presentation for getting a fast impression of the disk space used.
It’s a piece of software I have been missing many times in the past, but I never got around to implementing it. Now I used it as an opportunity for getting acquainted with some of the Boost libraries that I haven’t used a lot before. In particular dutree uses the following Boost libraries: Filesystem, Bind, Function, Lambda, and Iterator. I agree this might be a little overkill for such a small program (dependency wise, not performance), but knowing these very useful libraries makes for more effective development in other projects, so I think it pays off in the end.
This initial release is mainly for people who know how to build stuff themselves. A better build environment is planned for a future release. Click here to download the dutree source code.
Blog Software Update
August 5th, 2008This has been scheduled for quite some time, but today I finally got around to updating the software on this blog, including removing spam from the database (12,000+ comments). Now I have effectively blocked new spam attacks. Seems it was also actively being exploited to put hidden links to various sites in the posts — what a complete waste of time. I hopefully put an end to that now, at least for a while.
Yes, I know I should do this more regularly to avoid such problems, but I’m lazy when it comes to this. Not least because the process for updating the blog software is rather involved. It means I have to make a complete backup of the files and database, and create a patch with the customizations I’ve made against the old version. Then installing the new version, upgrading the database, fixing any problems caused by the upgrade, and then re-implementing the old customizations in the new version by inspecting the patch created earlier. Of course this task gets easier the more often it is done, so I should probably be doing it more often in the future.
Tracking Satellites with GENSO
December 14th, 2007
Normally I wouldn’t write here about what I do at university, but this is so exciting that I have to share it — videos below. 
Since September me and my group at Aalborg University (AAU) have been working on a project called GENSO (Global Educational Network for Satellite Operations). It’s an international project supported by ESA, NASA, JAXA, and other space agencies, and lots of people participate. For our project this semester at AAU we’ve been developing a ground station server for GENSO.
Maybe a short introduction to what GENSO is about would help. A basic problem when communicating with satellites is that you’re only able to talk/listen to a satellite while it’s over the horizon. GENSO aims to solve that problem by establishing a network of ground stations all over the world which are connected via the Internet. Using the network you will be able to communicate with your satellite whenever it’s above any GENSO ground station, and not only your own. Better yet, the GENSO network will collect data from your satellite autonomously whenever it passes over a ground station, and send a pass report to you with the data received.
GENSO is in its alpha test phase, and only downlink is implemented, i.e. you can’t transmit. But still tracking satellites requires lots of stuff going on at the ground station, like predicting when satellites are passing, controlling antenna rotators and modems, and setting Doppler corrected frequencies on radios during a pass etc. This and more is what the ground station server is taking care of.
The cool thing about it is that now the project has reached a state where you can actually just start the ground station server, leave the server and the hardware alone, go somewhere else and wait for data rolling in once a satellite is over the ground station. We even implemented a live audio stream that you can connect to during the pass to hear what is received by the radio.
We already made a number of successful proof of concept passes at workshop V here in Aalborg back in early November. (Actually the picture to the right shows the participants at the workshop enjoying a celebratory roof-beer while the ground station is controlling the antenna behind us during a pass.) But not until now the system has been running completely autonomously exclusively on the hardware available at the AAU ground station.
What I’d like to show you is a couple of videos showing part of a CO-57 pass over the AAU ground station. I followed the pass from my computer at home, and no human interaction with the ground station was taking place.
Videos:
Video 1 (5.36MB) | Video 2 (33.2MB)
Pictures:
What you see on the screen in the videos and on the pictures above is: Upper left: Web-cam in the radio room at AAU. Lower left: GPredict running locally (just to see which satellites are available). Upper right: Debug output from the ground station server (setting azimuth, elevation, and radio frequency). Lower right: The GUI of the ground station server showing the passes that are scheduled within the next hour at the bottom. (The red bar to the left indicates the current pass.)
Dell UltraSharp 2407WFP 24″ Widescreen
July 27th, 2007
Long time, no updates. It’s not that nothing is happening, though. Lots of small projects, but none worth showing off (yet at least). Anyway, I just have to brag about my new screen, so here it is.
As it says in the headline it’s a 24″ widescreen, i.e. it is damn big. I’ve been reluctant to buying an LCD flat panel for years because I never found their colour representation to be anywhere close to my good old Trinitron CRT. Things have changed, though, and when I came to think about it I don’t require exact colours in any of my daily work anyway. On the other hand, what I absolutely must have is lots of screen estate and fast response time.
It appears I got all three things: great colours, high resolution (1920×1200), and fast response time (6ms grey-grey). And not the least, the image is ultra sharp, which certainly wasn’t the case with my CRT, so the name is in fact not lying. As the display on my laptop has the same resolution I now effectively have a desktop of 3840×1200 pixels, which should suffice in most cases. Actually I wasn’t sure until I tried that my graphics adapter could handle two displays at that resolution using DVI-D. Nice surprise.
Well, I had been thinking about buying a flat panel for some time, but it wasn’t until I stumbled across an ad from Dell I started looking into it. I spent some time reading reviews, and it appears that the 2407WFP is competing with Samsung’s 244T. From what I understand they’re using the same (Samsung) panel, but the Dell has more facilities and connections and comes at a lower price.
Most of the reviews mentioned problems with banding, streaking, and blurry text on the Dell, especially on the earliest firmware. I haven’t seen any of these problems; the image quality is absolutely top notch. And what an awesome experience it is when gaming! No problems with response time whatsoever. I truly recommend this screen.
Here are some pictures showing my new and old setup, and a close up of some text to refute that the screen blurs text. Click the images to enlarge.
A little snow (and AutoStitch)
February 26th, 2007
Well it’s starting to thaw now, but since last Thursday large parts of the country has been nearly in state of emergency because of heavy snow (by the standards here). Thursday until Sunday it has been almost impossible to get anywhere. All bus routes were cancelled for four days, but not completely without reason; see the picture to the right. This was the first real snow this winter, so maybe it came as a surprise for those responsible for snow removal.
Anyway, I just wanted to share this little gem. It’s a program called AutoStitch, which makes it really easy to create panoramas from a series of pictures. You basically just point and shoot a series of pictures that overlap a little, and when they’re fed into the program it automatically figures out how they fit together. It works really well and is damn fast compared to other panorama software I’ve used before. Below are some panoramas I made with it. (I cheated a little with the sky, because the originals didn’t cover enough—that’s also why the composition is a little messed.)
Fast motion candle (camera control)
January 21st, 2007
I’m still alive, although it’s been 5 months since my last post. I’ve been busy with university and work the last couple of months, so there hasn’t been much time for Ogre or other projects lately.
Anyway, just for the fun of it, I recently bought Olympus SDK to play with controlling my (rather old) C-5060WZ from the PC. It’s not the best piece of software I’ve seen, but it wasn’t that expensive either and seems to work just fine. It allows you to control much of the camera’s functions programmatically from the PC, i.e. setting focal length and lots of other settings, capturing pictures, and downloading/managing picture files etc.
Inspired by BBC’s Planet Earth, where they show e.g. plants growing in fast motion, I hacked together a small application capturing a picture of a small candle every 15 seconds. You can see a video of the result by clicking on the picture to the right of this text. The 33 seconds of video are made from 264 pictures taken during a period of about 1½ hour. Then there was no more space left on the CF card in the camera. Next time I’ll have to delete the pictures after having downloaded them – and find a more interesting scene.
Ufo udpate and X-3D
August 20th, 2006
At long last I got my new X-Ufo a couple of days ago. It was returned to Amazon the first time around, because only 3 of 4 motors worked. The one I just got didn’t work either, unfortunately, because the gyro was defective on arrival. Anyway there’s hope, because I took the gyro from the old ufo and replaced the faulty one, and now it works.
This means I have a spare ufo, but not for long. Because, in the beginning of September I get my X-3D board. 
It is a purely electric gyroscope that doesn’t have any of the constraints of mechanical gyros. I’m really looking forward to this, as it should improve the experience tremendously – with practice you can even do loops. And it’s possible to customize the settings through an USB connection to your computer. You just have to watch some of the “Piezo in perfektion” videos by the people behind this board! Very impressive; can’t wait.
Flying the X-Ufo
July 17th, 2006
Some weeks ago I bought an “X-Ufo” which is kind of a remote-controlled helicopter with 4 rotors. It’s great fun to fly but it takes a little practice to control it in the beginning, and the ufo inevitably takes some hard crashes. It’s for indoor and outdoor use, but I learned after chopping a couple of my plants that it was best to keep it outside. Unfortunately that requires next to no wind.
A couple of days ago some friends visited, and one of them got the idea to mount a mobile phone with a camera underneath the ufo. This resulted in some quite funny videos, some of which you can watch here. The phone survived, but at the end of the day, the ufo didn’t fly that well, so there’s a new one on its way. I can always use this one for spare parts.
Next thing, if money and time allows it, will be replacing the batteries with some larger capacity ones – the flight time is about 5 minutes currently – and a gyroscope replacement if possible. The gyroscope sitting on it is mechanical, and when the ufo is tilted more than around 20 degrees, it looses track of what is horizontal, and the ufo will crash. It appears it is possible to mod the ufo by replacing the gyroscope with a custom “piezo” module that has no mecanical parts and provides for better control. In fact “LiPo” (batteries) and “piezo” appear to be the buzzwords over at the X-Ufo forums. My German isn’t very good, but hopefully we’ll be able to get some hints from that source.
Click one of the pictures to the right to see some pictures and videos of the beast in action.
