{"id":2571,"date":"2015-05-15T14:03:56","date_gmt":"2015-05-15T05:03:56","guid":{"rendered":"https:\/\/regex.info\/blog\/2015-05-15\/2571"},"modified":"2016-06-05T01:07:03","modified_gmt":"2016-06-04T16:07:03","slug":"more-gps-cycling-tests-things-are-pretty-bad-and-theres-little-hope","status":"publish","type":"post","link":"https:\/\/regex.info\/blog\/2015-05-15\/2571","title":{"rendered":"More GPS Cycling Tests: Things are Pretty Bad and There’s Little Hope"},"content":{"rendered":"\n\n
<\/a>\nNikon D700 + Sigma “Bigma” 50-500mm OS @ 50mm — 1<\/sup>\/<\/big>1250 sec, f<\/span>\/8, ISO 560 —\nmap & image data<\/a> — nearby photos<\/a><\/span>\nTop of Mt. Otowa (\u97f3\u7fbd\u5c71)<\/span><\/span>\nKyoto, Japan\n\n\n\n\n<\/div>\n\n

I made my second cycling run up Mt. Otowa (\u97f3\u7fbd\u5c71)<\/span> on Wednesday, the first<\/a> having been two\ndays prior in the gloomy late afternoon just before a typhoon<\/span> came through.\nWednesday's was the first afternoon after the mild typhoon passed, so I\nexpected<\/span> the air to be really clear (like this<\/a> and this<\/a>), so I lugged<\/span> my Sigma “<\/span>Bigma”<\/span> 50mm~500mm\nzoom<\/a> all the way up there, along with the 2×TC to give me a 1,000mm lens<\/a>.<\/p>\n\n

It was so<\/i> not worth it... it was the most hazy I'd seen it in ages.<\/p>\n\n

<\/a>\nNikon D700 + Sigma “Bigma” 50-500mm OS @ 100mm — 1<\/sup>\/<\/big>1250 sec, f<\/span>\/13, ISO 800 —\nmap & image data<\/a> — nearby photos<\/a><\/span>\nSuper Super Hazy<\/span>\nI was there for an hour, and could never even find Kyoto Tower\n\n\n\n\n<\/div>\n\n

The only things that were sort of clearly visible were close, just near the foot of the mountain.\nThis is a gas<\/span> station that I pass<\/span> by along the way that marks an increase in the steepness of the route...<\/p>\n\n

<\/a>\nNikon D700 + Sigma “Bigma” 50-500mm OS @ 1000mm — 1<\/sup>\/<\/big>1250 sec, f<\/span>\/13, ISO 1800 —\nmap & image data<\/a> — nearby photos<\/a><\/span>\nStarts to Get Steeper Soon<\/span>\n\n\n\n\n<\/div>\n\n

As the crow flies it's about 2,580m (1.6mi) away, but due to how the road winds up the mountain,\nthe covered distance is about three times that. It took me<\/span> about 49 minutes to make it from there,\nand about 23 minutes to make it back down.<\/p>\n\n

(If find it shocking that the return trip takes only half the time; it feels like it takes about 1\/10th the time.)<\/p>\n\n

In the spirit of “<\/span>The Voodoo of Elevation Gain\nand Strava (and How I Get<\/span> Around It)<\/a>”<\/span>, I brought<\/span> three GPS\/GLONASS\nunits with me, using various ways to extract nine different tracklogs...<\/p>\n\n
Device<\/th>Tracklogs<\/th><\/tr>\n
Apple iPhone 6+<\/td>\nVia the Strava<\/a> app.\n\nVia Abvio's Runmeter<\/a> app.\n\nVia the Runtastic<\/a> app.\n\nVia the\nGalileo Offline Maps<\/strike> (Name changed Feb 2019 to Guru Maps<\/a>) app.\n<\/td><\/tr>\n\n
Garmin eTrex 20<\/td>downloaded from the device<\/td><\/tr>\n\n
Bad Elf GPS Pro +<\/td>\nDownloaded via their app, with GPS elevation.\n\nDownloaded via USB, with GPS elevation.\n\nDownloaded via their app, with barometric elevation.\n\nDownloaded via USB, with barometric elevation.\n<\/td><\/tr>\n<\/table>\n\n

Now in theory, all four iPhone apps should produce the same tracklog because they all share the same\niOS Location Services data, but they're all quite different. Runmeter<\/i> (which is identical to their\nCyclemeter<\/i> and Walkmeter<\/i> apps except for the name and icon) has an option to use the iPhone's\nbarometric altimeter, and as the Voodoo<\/i> post explains, the Strava app ignores both iPhone altimeters,\nbut elevation aside, the latitude\/longitude tracks among the four should be identical, but they're far from it:<\/p>\n\n

\nThe Four “<\/span>Identical”<\/span> iPhone-app Tracks\n<\/div>\n\n

Part (all?) of the problem is the sampling frequency. Of the four<\/span> iPhone apps, the most frequent logger is\nGuru Maps<\/i>, which creates a\ndatapoint<\/span> every second when there's obvious movement. The other<\/span> three apps sample the location “<\/span>every so often”<\/span> in\nways that can lead to some big errors. For example, Runmeter's didn't put a\ndatapoint<\/span> for where I stopped<\/span> my ride until more than 30 seconds after I\nhad<\/span> stopped<\/i>, making it look as if I was<\/span> 30+ seconds slower than I\nactually<\/span> was. Adding 30<\/span>+ seconds to a segment<\/span> can destroy the effort (e.g.\na hill<\/span>-sprint that takes a respectable<\/span> 90 seconds gets recorded as a pathetic<\/span> two minutes.)<\/p>\n\n

Even more odd are the four tracklogs from the Bad Elf GPS Pro+<\/a>. On the plus<\/span> side, it records a\ndata<\/span> point once every second (and can be configured to record 10 per\nsecond!), and also, it records altitude two ways (satellite and\nbarometric). Because of that last feature, in extracting its data, I'd expect\none<\/i> track with two<\/i> elevation profiles, but as odd as it\nseems, one can actually derive two<\/i> different tracks with four<\/i>\nelevation profiles. You see, tracklogs can be pulled from the device via\ndirect USB connection, or via its iOS app. One\nwould<\/span> think that either method is just transporting the same data,\nbut they inexplicably give different data. I then\nsplit<\/span> each into two tracklogs, one with the satellite altitude, and\none with the barometric altitude. So we end<\/span> up\nwith two tracks with four different elevation profiles. Bizarre.<\/p>\n\n

(I so<\/i> wanted to like this unit, mostly because the company seemed to have a clue<\/span> and\nwasn't Garmin, but with so many little problems like this cropping up, I have to<\/span> finally admit\nthat I can't<\/span> recommend the unit.\ud83d\ude41<\/span>)<\/p>\n\n

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Anyway, I have nine tracklogs, and of course none of them agree on the\namount of vertical gain. This problem likely stems from the aforementioned\nsampling frequency, and also the data source (barometric or satellite\naltimeter) and post processing. Here's a look<\/span> at the tracklogs, their\nresulting plot in Google Earth, and various claims about the vertical\nclimb: what the app itself claimed, what my software calculates, and what\nGoogle Earth calculates...<\/p>\n\n

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