Garmin Forerunner 305 GPS Accuracy Revisited

Back in 1812 when Garmin released the Forerunner 305, I was young and fast and the world was a generally better place. OK, putting the Napoleonic Wars to one side, ‘the past’ really was a better, faster and more accurate place for many of us.

Or so it seemed.

Note: This article is republished from 2017 and coincides with yesterday’s DCR-retro-review of his Forerunner 305 and the 15th anniversary of the FR305 release. There is not a Fenix 7 coming out so neither of us has anything better to do with our time.

Garmin’s Forerunner 205/305 watches were, at the time, popular watches and, to be fair, they were ahead of the sports tech curve even boasting triathlon features as well as GPS. The 305 put Garmin on the path to the sporting watch dominance that they now enjoy. All because they probably sold vast numbers of the 305 and then similarly large numbers of the Edge and Forerunner 910/310 models that followed. From there Garmin moved to the money-spinners that were the Edge 8xx, Edge 5xx and Fenix 3. The rest, they say, is history.

I have this recollection of the Instant Pace on the Forerunner 305 nearly always being ‘spot on’ and I relied on it every week as one parkrun 5k PR/PB after another fell. Ah yes. The good old days. In some ways, the Forerunner 305 probably also got me started on this blog by getting me more focussed on running than I had been in the even earlier and even more glorious years that preceded the 305’s launch.

Anyway. Is the Forerunner 305 REALLY any good? (For GPS)

It’s packed full of SirfStar III GPS chip goodness and I don’t think Sirfstar progressed much beyond version V (a la Suunto SPARTAN and Polar V800) before the GPS chip world lurched toward Sony. Of course, despite few new chips we are still using the exact same GPS satellites, it’s just that occasionally we might throw in a few satellites from GLONASS or Galileo constellations.

Newer chips such as the Sony are widely thought to have compromised quality in favour of power-saving. Is that why GPS accuracy was better in the good old days? Perhaps instead it is because newer, more compact watches have smaller antennae? Indeed those of you who remember the 305 will certainly remember its size, it certainly WAS NOT compact. Indeed the 305 was packed full of a whopping battery and signal-grabbing antennae similar in size to the average household satellite TV dish 😉 (ish)

I put the 305 through my GPS test when this post was first published in 2017. The 305 is only ever going to have one shot at the test as it’s quite a way to run and other more interesting things are always around the corner for my wrists.

The test is a hard one. (Details here). The raw FIT/TCX GPS test files of ALL devices are available (here) in a public folder along with an analysis spreadsheet of the summary results (there are three tabs in the spreadsheet).

The result?

A: 73%. I was a bit generous. For old times sake. Now you know.

But that was an acceptable performance. On a par with the Suunto ULTRA when first released and notably above the Garmin Fenix 5X and even above the V800 when the V800 is worn on the underside of the wrist. The reality is that this result is at the lower end of acceptability. Sorry, I’ve dashed your dreams. It is notably below the SPARTAN SPORT and POLAR V800 (the latter when worn properly) which are in a different class.

Also when running at a constant pace I am sorry to say that there WAS notable instant pace variation by the ‘industry-standard’ +/- 30secs/km, or slightly more, on the underestimating side and 5-10 secs/km on the over-estimating side. When running at a constant pace in open skies it WAS pretty good though. But then again, most sports watches are. Even in the glory days, I did have a footpod albeit a Garmin footpod not a STRYD.

The 305 got the overall distance accurate to near-enough +/-0.5%…again that’s pretty normal.

Please feel free to reminisce below and start every comment with “Ahhh! when I were a lad/lass we could only afford coal for breakfast”