Audio Coach reports Elevation. Does it use settings in Altitude Manager?

Taras D shared this question 1 year ago
Answered

Question: When reporting Track Elevation, does the Audio Coach use the settings in Altitude Manager?

Problem: The Audio Coach (V3.22) can now periodically report Track Elevation. However, I believe the reported elevation may be sourced directly from the GPS and does not use the settings in Altitude Manager.

Description: I've used several navigation apps on my phone and none have calculated an accurate value for Total Ascent (Total Elevation Gain). The final result is usually an inflated value that is far higher than the realistic value recorded by a barometric altimeter.

The solution I've used in the past is to import the track into Runalyze or Garmin Connect, which ignore the track's elevation data, and calculate the total ascent using a Digital Elevation Model (DEM) using SRTM or Google. What I like about Locus Map is it can also do this, using SRTM, via the following setting:

Settings > GPS and location > Altitude Manager > Settings tab > SRTM Data > Replace GPS values

When I use this setting, the calculated total ascent is conservative and realistic.

I just tried the new Audio Coach and had it report Track Elevation. Over the course of a ~5 kilometer walk on nearly flat terrain, the final reported Track Elevation was 50 meters. This is far too high a value.

The Track's Statistics page shows more realistic results (using SRTM data exclusively):

Elevation (Downhill): -20 m

Elevation (Uphill): 19 m

To demonstrate the terrain's "flatness", the reported min/max altitudes are 29 and 35 meters.

Would it be possible to have the Audio Coach report Elevation according to the settings in Altitude Manager?

Comments (5)

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Good day Taras,


Locus Map use two steps before some final elevation values are visible. First step are all possible settings defined in "Altitude manager". These settings are applied always directly on measured elevation values, so they are always used, there is no exception.

Second step is small filtering algorithm that make recorded/measured values more fluent. This filter has anyway two versions. First is not so precise and is used directly during recording. Second a lot more precise is used once recording is finished and Locus knows all measured data. Btw. same system is used also on all other values like speed, gradient etc.

What I wants to say is that you may check these elevation values in currently recorded track just before you save it. Values should be exactly same as you hear from Audio coach. Once you save track to database permanently, values are once more optimized by advanced filter so they may be more "precise" (fluent).


Was my longer explanation clear? There is always space for improvements and this is no exception ...

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Thank you!

If I understand you correctly, the settings in Altitude Manager are always applied but there is a two-step filtering process for elevation:


  1. During track-recording. Imprecise. Reported by Audio Coach.
  2. After track-recording. Precise. Reported on the Statistics page.

Unfortunately, the first filtering step is, like you explained, not very precise. Near the end of my walk it reported 50 meters and that's higher than anything reported on the Statistics page (results of second step).

The route I walked is very flat. If I import the track into Runalyze and use GoogleMap's DEM, the total ascent is 30 feet/9 meters (and it reports 0 feet if I use SRTM).

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Too bad my phone doesn't have a barometric altimeter! That tends to produce more consistent and realistic elevation measurements than GPS.

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What happens when the barometer is selected in the Altitude Manager. And at SRTM Data> Replace GPS values

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In that situation, I guess Audio Coach would report elevation measured by the barometric altimeter. When the track is saved this option "SRTM Data > Replace GPS Values" would cause Locus Map to replace the elevation values with data from SRTM.

If my phone had a barometric altimeter, I probably wouldn't use "Replace GPS Values".

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@Taras D: you precise description is precise. Problem is as usually in filtering algorithm that is used DURING track recording


@freischneider: order of operations is same as in "basic" tab of "Altitude manager" screen. So firstly is applied offset, then optimization based on SRTM files.

If you then have enabled "Pressure sensor" it is applied as third step. In case of "Automatic calibration", SRTM data are always used if available so previous "SRTM data" settings has no effect. And last is filtration ...