If you’re using your GPS and one of the applications that geotags photos based on a GPS track log you’ll have realised that it’s crucial to have the camera’s clock set correctly - otherwise the image locations will be shifted. If you’re lucky the software you’re using will allow you to specify the time difference between the camera’s clock and real (GPS) time. Here’s a tip for working out exactly what the camera’s time error is.

Find an accurate clock - the one in your GPS is good - or use your computer clock if it’s set to internet time. Now set the clock to display hours, minutes and seconds and take a picture of it with the camera. You’ll end up with something like this:

So now you have the time the camera thinks it was (in the image metadata) and the time the rest of the world thinks it was (in the picture). Subtract camera time from real time and feed the result into your geotagging software. In this case the camera thought it was 22:19:46 and the real world thought it was 23:19:27 so the error is 1 hour minus 19 seconds - or 3581 seconds.

The Wintec WBT-200 is a cute GPS receiver in a tiny package that streams NMEA data over Bluetooth and USB. It can also log GPS data for subsequent download. I’ve been using it to capture tracklogs for upload to Open Streetmap and I’ve been hugely impressed by the fast startup time and accuracy of the logged data.

The supplied software is Windows only but with a little fiddling you can get it working with your Mac or Linux box. Here’s how.

2006/08/06 Update: There’s a new firmware version for the WBT-200 (R4) that changes the data format used by the device (thanks G. Francisco for the tip-off). I’ve just submitted a patch to support the new format to Robert Lipe (gpsbabel). It should make it into the gpsbabel CVS within the next few hours. If you need a binary built with this patch for Windows, Linux, FreeBSD or Mac OS let me know.

I’ve got a load of geocoded images over at ShitShifter and I’ve been meaning to combine them with Google Earth for ages. Obviously it’s tempting to refer to it as a mashup but I’m not really sure it is.

Anyway you can see the results by downloading

http://hexten.net/maps/ss2.kmz

and double clicking on it (or adding it directly as a Network Link in Google Earth).

If you can’t see any images that may be because most of them are in the UK.

I picked up a Velleman K8055 USB I/O card the other day and was a bit disappointed that the only software that came with it was a closed source Win32 DLL and a simple control panel for the board. So I don’t have to boot into Windows to play with it I’ve produced a Mac OS X application that talks to the board. Here’s what the board looks like:

And here’s what the app looks like:

Thrilling stuff eh? Anyway you can download the source here: K8055-src-0.1.tar.gz or if you prefer you can get the application built on OS 10.4 (but believed compatible with Panther and maybe Jaguar) here: K8055.dmg. I’m going to move it to Sourceforge once the project registration is approved.

It doesn’t actually do very much at the moment - you can turn the outputs on and off and see the inputs change state. Next I’ll add Applescript support so you’ll be able to write simple scripts to control it and respond to events. I’m also thinking of producing a GPL (or LGPL) library that exposes the same API as the Velleman DLL but works on Windows, Mac OS and Linux. In the mean time if you want to write a Mac application that talks to a K8055 just rip the necessary code out source archive.

Update: The project has now moved to SourceForge. You can find it here: http://sourceforge.net/projects/k8055mac/. The initial release that’s there is the same as the release here.