Dave’s Tech Blog

Lindsay (eldest son) and I went Orienteering at Oakview, which is a property about 20km west of Armidale on the Bundarra road. We did a 3.5km “Short Red” course.

The GPS was carried to track our path. I think this is becoming a common enough sight at Orienteering events these days that people no long immediately assume you’re cheating.

Back at home the GPS is plugged into the (Ubuntu) PC via its own serial cable and a USB-RS/232 converter. To upload the track data:

gpsbabel -t -i garmin -f /dev/ttyUSB0 -o kml -F FILE.kml

There are usually some breaks in the path due to the device losing contact with the satellites. Currently a text editor is used to rudimentarily merge them into a single path. The resulting file can be imported into Google Earth to (re)view the path.

It can also be uploaded to Google Maps to make a sharable map.

In addition, there are sites like gpsvisualizer which allow you to upload the file and have it converted to various formats – including an elevation profile:

Note that our 3.5km course (measured by straight lines between the controls) ended up being about 4.5km.

Heavy overnight rain swelled the creek on our property and we went for a walk with the digital camera to take photos. Three videos of the flow were also taken.

Son #1 seemed a bit bored so he was set the task of finding a program (for Ubuntu) to stitch the three videos together into one – along with some static text between each one. He found Kdenlive and it, and he, did a brilliant job:

[kml_flashembed movie="http://www.youtube.com/v/KyJWyyJEocA" width="425" height="350" wmode="transparent" /]

In case the embedding doesn’t work, here’s a link to YouTube: Toms Gully Creek near Boorolong Road – 31 July 2010.

The creek has a mostly perennial flow, but will stop flowing during extended dry periods – such as one that only finished a few weeks prior. It was certainly a stark contrast.

Toms Gully Creek is a tributary of the Gwydir River including the Copeton Dam which is at 6% capacity. Hopefully this will knock that up a bit.

I’ve been working on an interface between two systems.

The interface has to watch system A and send transactions to system B. Normally, in the Oracle universe, there would be 2 ways to do this:

1. Use database triggers on System A’s tables to trigger transactions
2. Keep a separate record of the state of System A’s tables and compare it to the actual state – looking for differences which trigger transactions

The drawback with the first method is the performance hit of the database triggers on System A, as well as the possibility they might introduce errors into its processing.

The drawback with the second method is that replicating parts of the watched system is, well, just plain yucky.

Fortunately, in the case of this particular interface, System A uses a column called UPDATE_ON in its major tables. This column is updated whenever there is a change in the row. This means the interface just has to look for rows where UPDATE_ON is greater than when it last looked. It’s a much lighter touch than the other methods.

I encourage Data Architects everywhere to include an UPDATE_ON on their major tables in their designs – even if it’s usefulness isn’t immediately apparent.

For the sarcastic …

http://lmgtfy.com

Here’s an example of it in action:

http://www.lmgtfy.com/?q=let+me+google+that+for+you

Blackle is a front-end to Google search which aims to save energy by using a black background instead of the usual Google white.

Even though there is skepticism about the energy savings, it’s a good message.

On February 13, 2009 at 23:31:30 UTC, the Unix time number will reach 1234567890 seconds (since 1/1/70).

Reminds me of a few years back: 12:34:56 on 7/8/90.

On Linux you can type date +%s to see the “count-up”.

“Appnr is a web-based tool and a service that installs applications on Ubuntu. This is a web interface for APT, and the package is downloaded and installed from Ubuntu/Third-party repositories.”

You know, some people just have too much time in their hands. Good thing they use it to build cool things like ASCIIQuarium.

If you use Ubuntu I’ve packaged and uploaded it here. A package for the perl library that asciiquarium depends on is here.

In my (copious – I wish) spare time I contribute in minor and probably annoying ways to a project called INX which stands for “Is Not X” (and is pronounced ‘inks’). It’s a Linux distribution designed to teach the command-line and some of its tools in an easy and fun way.

Today it reached its version 1.0 release (click on this text to learn more).

Congratulations Peter!

http://cryopid.berlios.de/

Many many occasions in which this would have been so useful. Read the “Use Case Examples” on that page.

As described by the CLUGer who posted about it: “for that ‘screen moment’ where you say to yourself ‘I wish I started this from inside a screen session’.”