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Waypoint and CoursesDownloads: 1,161 •
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old_man_biking wrote:This IS already implemented - by Waypoints and Courses plugin.
The plugin provides an Add/Fix elevation action which tries to determine the type of elevation error first:
1. "noisy" GPS elevation with
2. drifed barometric elevation
In case 1 the plugin will replace the elevation track by DEM elevation - with all its limitations
In case 2 the plugin will use DEM elevation to remove the drift but maintain the fine resolution of the barometric elevation
The next plugin version will add another compensation: when there's a waypoint near the activity start, it will use its elevation as the start elevation.This can compensate drifts of the barometric altimeter while the GPS was turned off.
old_man_biking wrote:I couldn't have explained that better
@justintime: try it out, it works well
dbrillha wrote:I have the latest W&C plugin, and use a 910xt.
Most of the time, it does not detect that the data is barometric, and simply overwrites my baro data with digital map data. I'm not sure how it determines if it is baro or not. Sometimes it does detect baro and then offers to compensate drift. But the algorithm is unreliable. Not sure if I can check some box somewhere to force baro compensation, since from now on, I'll always import 910xt data with baro information.
Even when it does compensate for baro drift, there are three enhancements that would make this a phenomenal algorithm and much more accurate.
1. If there is Weather data, then it can use the actual pressure change over the duration of the workout, and use this to modulate the drift. For example, 3 hours into a 6 hour ride, a front might come in, with a significant and fast shift of pressure. Knowing that would make the drift compensation much more accurate than assuming a linear drift across all 6 hours.
2. It seems to have logic that says: if the end and start GPS location is very close, force the elevation to be the same. But this logic could be used across the entire data set. For out and back, or loops, or where you cross over the same path (at intersections, junctions), the elevation should be the same. After compensating for atmospheric pressure drift, the second pass could make sure that when you were ever at the same general spot, your elevation was the same. Possibly taking the average of the 2 (or more) readings at the same place.
3. Possibly give an option for the user to enter a KNOWN starting and/or ending elevation, rather than count on initial calibration of the pressure or GPS. For example, I may start a trail run without calibrating my baro sensor. But after the fact, I can determine the actual elevation of my start and end point (might end at a different location). It would be great to be able to tell the correction algorithm my actual start/stop elevations.
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