binary stumble

This post is an adaptation of an email I was sending to someone who wrote to me to ask about doing what I do. I directed him to this previous post (What GPS to use) and started off clarifying a couple of things:

eTrex (on its own with no further letter) used to be a product that Garmin did. They now produce something called an eTrex H with a high-sensitivity chip. It’s their most basic model. They’ve been selling eTrexs for years. It works well but as I mention in that earlier post, it needs a proprietary cable. Here’s a link to a homebrew version in the blog if that’s up your street.

I don’t own an iPhone and probably never will, not agreeing with how they go about business. I do have an Android phone courtesy of the MRL that Soph and I are using for our mood reporting but because I have a GPS on me anyway from way before smart phones were around, I have little or no experience in this area. If anyone reading this has some experience using GPS applications with smart phones, I’d love to hear them.

Something that is important to me and that I would certainly bear in mind if I was to look at smart phone GPS logging apps is how it lets you keep your data if at all. I’d avoid anything that had some funky web application or internal viewer that was the only way to look at your tracks. Look for export of tracks in gpx format. It’s the most useful and translatable way of saving gps data (if a little verbose). There are plenty of good open source applications that handle gpx.

As to my comments about battery life and robustness. There’s nothing more disappointing than coming back from a hike and discovering that your iPhone ran out of battery a quarter of the way through. By robustness I mean an app that will not freeze or crash. The great thing about having a piece of technology that does only one thing is that it generally does not freeze or crash, especially if it is as basic as the Garmin eTrex.

On a technical level, I am a little dubious about smart-phone GPS logging apps because I increasingly care about how they arrive at position, what data they keep and what they throw away. Heaven knows this is already an issue in an eTrex, but a smart phone app developer can make many decisions that can have a large effect on your tracks. Snapping your track to a ‘known’ road could be one very undesirable intervention. Making overly crude assumptions about the speed you are moving is another that can adversely effect the shape of what you know you did. I know they do it to help iron out some difficulties in providing an accurate position but it is often not documented or made transparent. I would like minimum interference on this and clean up anything afterwards if necessary. (This is where Mathieu’s gps cleaning software will come in)

On the other hand, there is the adage-turned-iPhone-app that the best camera is the one you have with you. What I mean to say is that it might be good to have an app on your iPhone ready to go so that when you find that you’ve forgotten to pack your GPS, it can be a backup.