Tag Archives: GPS

Sonic Bikes to Sonic Kayaks – using puredata

When I first started working on the Sonic Bikes project with Kaffe Matthews in 2013 I had just moved to Cornwall, and I used the Penryn river for developing “The swamp that was” installation we made for Ghent. We’ve always talked about bringing this project here, but the various limitations of cycling (fast roads, stupid drivers and ridiculous hills) were always too much of a problem – so we wondered about sonic kayaks, as a distant vague idea. However now, thanks to help from the British Science Association, Feast Cornwall and the Port Eliot Festival they are fast becoming a reality!

We’re also using this opportunity to convert kayaks into instruments for sensing marine microclimates – an area which is currently lacking in scientific knowledge. In order to do this, we need to expand the sonic potential of our current system – moving it from sample playback to a more open ended synthesis approach. We’re running a open hacklab to trial the use of sensors, and actually get out on the water with Kaffe later in the month.

zones

To do all this – and keep it functioning on a Raspberry Pi, we’re using Pure Data. For the moment it seemed most appropriate to stick to the concept of audio zones, previously these defined areas associated with samples that would play back when you were inside of them. The screenshot above is the sonic bike mapping tool – recently rebuilt by Francesca. Using Pure Data we can associated each zone with a specific patch, which leaves the use of samples or not, effects, interpretation of sensor data and any other musical decisions completely open.

pd

The patch above is the first version of the zone patch mixer – it reads OSC messages from the GPS map system (which is written in Lua) and when a patch is triggered, it turns on audio processing for it and gradually fades it up. When the zone is left it fades it down and deactivates it – this way we can have multiple overlayed patches, much like the sample mixing we used before. We can also have loads of different patches as it’s only processing the active ones at any one time, it won’t stress out the Raspberry Pi too much.

I’ve been testing this today by walking around a lot with headphones on – this is a GPS trace, which gives some ideas of the usual problems of GPS (I didn’t actually switch to kayak halfway through, although it thought I did).

trace

New Portuguese Bicycle Operatics

Prepare your bicycle clips! Kaffe Matthews and I are starting work on a new Bicycle Opera piece for the city of Porto, I’m working on a new mapping tool and adding some new zone types to the audio system.

While working on a BeagleBoard from one of the bikes used in the Ghent installation of ‘The swamp that was…’, I found (in true Apple/Google style) 4Mb of GPS logs, taken every 10 seconds during the 2 month festival that I forgot to turn off. Being part of a public installation (and therefore reasonably anonymised :) – this is the first 5th of the data, and about all it was possible to plot in high resolution on an online map:

It’s interesting to see the variability of the precision, as well as being able to identify locations and structures that break up the signal (such as the part underneath a large road bridge).

The Swamp that was, a bicycle opera

Day one on a new project – with Kaffe Matthews, and a collaboration between FoAM & Timelab, “The Swamp that was” is an opera where bicycles become a way to hear stories of the past in the city of Ghent.

I’m picking up the software side of things from Wolfgang Hauptfleisch, which involves using BeagleBoards – low power self contained open hardware ARM computers, a good follow up to my experiments with the considerably more closed NDS and less general purpose Android.


This is my test BeagleBoard xM in a custom laser cut housing from Timelab.

The “swamp” system is based on lua scripts calling proteaAudio for realtime audio processing. Lua has a tiny footprint and is great as an embedded interpreter (despite indexing from 1 and other minor gripes). Everything seems to be up and running, and I’ve set up a project on gitorious with the sourcecode.

Some random things I’ve learned include: flags to speed up dd copying images to extremely slow usb SD memory cards:

sudo dd if=swamp0-1.img of=/dev/sde oflag=dsync bs=1M count=1024

List ip addresses of devices attached to your local router:

sudo arp-scan --interface=wlan0 192.168.1.0/24

I’m using the Ångström distribution on the beagle board, which uses opkg for package management – it took me a long time to figure out the best way to search for packages is simply:

opkg list | grep alsa