405cx – anderswallin.net

Garmin 405cx aboard an IOM

The 405cx gps-watch is small and light enough to just tape to the aft-deck of an IOM. Today's event in Tampere had 12 races but I missed a few due to electrical problems. Races 1 and 2 above, and races 7-12 below. It's funny how google-maps and google-earth show permanent winter and ice in Tampere 🙂

The raw-data (tampere_gpsdata.zip) is available in TCX format as well as Google-earth KML format from the garmin connect website.

Anyone have any software or matlab code to extract the instantaneous speed from this data and plot it? Might be useful for further CFD investigations or VPP-programs. Mostly light and shifting no1 rig the whole day. It will be interesting to compare with no2 and no3 rig in a real breeze.

Are there even smaller and lighter GPS-dataloggers? How long before we can have a GPS on every boat and watch playback of the race afterwards at home?

8k run

An easy jog home from work. The Garmin has an auto-lap feature which takes lap-times each kilometer.

This time the N95 trace (yellow) seems less jumpy, but there's still a difference compared to the Garmin:

Garmin: 8.28 km in 50 min 50 s, 633 kcal
N95: 8.35 km in 50 min 55 s, 731 kcal

A second GPS test

A secodn GPS test, this time with the 405cx on my left wrist and the N95 in my right hand. I had hoped this would expose the N95 antenna and improve its performance. Not so. The red trace (405cx) still looks much better while the yellow one (N95) jumps wiggles and snakes around. The summaries are:

N95: 8.30km in 53 min 13 s, 727 kCal
405cx: 7.92 km in 53 min 31 s, 627 kCal

If you zoom in, the N95 has me walking on water. To be fair the 405cx also looks a bit lost at the beginning of the run (far right), but it does get the street-crossing spot on (middle-right in the pic).

Then for a straight bit along 'Nokia avenue':

That's not pretty. I guess you could argue that on the way out (top) the street has tall houses on both sides, so the N95 (yellow) has a hard time finding satellites, while on the way home (bottom) it's more open and both GPSs perform roughly the same.

Here's part of the route in more open terrain. That seems to confirm that the N95 needs wide open spaces to do well.

For the record, my N95 8GB runs V 15.0.015 firmware (which I've several times unsuccessfully tried to update with Nokia PC-Suite 🙁 ) and I'm using Nokia Sports Tracker v2.06 (S60 3.1). Today I had GPS-filtering turned off in sports tracker.

Somewhat surprising results! I would have thought GPS-positioning is a plain-vanilla technology by now and every company does it with equivalent hardware and software. Apparently not, or the N95 antenna is really inefficient, or I'm doing something wrong...

N95 vs. 405cx GPS test

GPS-running is so fun I decided it's time for a new toy: A Garmin 405 cx ! Out on a walk we go, comparing the N95 running sports-tracker with the 405cx.

Here's a test where I wore the 405cx (red trace) on my wrist and the N95 (yellow trace) with sports-tracker running in my pocket. I didn't turn them both on exactly at the same time, but there does seem to be a difference in the distance and kCal values. In addition to the time/distance data the 405cx also uses heart-rate data for computing calories.

N95: 6.58 km, 1h 4 min, 576 kCal
405cx: 6.32 km, 1h 7min, 324 kCal

The N95 GPS data is much more wiggly, as seen in this picture of a long straight bit of the walk:

That probably also explains the extra distance on the N95, since the wiggles never go away:

Although the GPS-Filtering was set to "High" on the N95, it shows strange jumps along the shore-line where the satellite visibility to the South should be OK.

Here it looks like the N95 position (yellow) fix is first a lot to the east, and then significantly south of the bridge I actually crossed. Then for some reason the 405cx (red) and the N95 agree again. I think the 405cx samples position at 4 s intervals, so some cutting of corners is understandable.

This test wasn't entirely fair since the 405cx was on my wrist while the N95 was in my pocket. I need to re-do this test with the N95 and its antenna held at a similar height/visibility compared to the 405cx.

Garmin is doing a lot of things right with the 405cx: No extra GPS-pod like with the Polar products, a set of nice youtube-videos practically replace the manual, charging through the USB-port(why doesn't the N95 have this?), to name a few.