Elevation Correction

ActivityLog2 supports fixing elevation data in imported activities, resulting in better looking elevation graphs, more accurate calculation of total ascent/descent summaries, and calculations of derived series, such as Grade Adjusted Pace (GAP).

There is a blog post on why this is needed and how this works, but the summary is that elevation correction is needed even for devices that have a Barometric Altimeter (most modern devices these days), since altitude readings are affected by changes in atmospheric pressure due to weather changes. This means that the same route traversed in activities on different days will have slightly different elevation profiles.

Elevation correction works by looking at nearby points from all activities, regardless of time, and averaging the altitude for those points. That is, ActivityLog2 averages the altitude from a route you did today, with points from routes done in the past, that cross the same locations. This algorithm uses only data from the training database, and does not require making network requests to external API services.

The correction works best when the same areas are covered repeatedly, which is usually the case when training; however, even a single "out-and-back" route will be able to take advantage from the fact that there are two readings for every point, one on the out section, and another one on the back section.

Corrected Elevation data is added as a separate data series to each activity, and graphs are available for both the original and corrected elevation. The original elevation data is never removed from the activity and it is always available for visualization, but summary elevation values, such as total ascent are calculated from the corrected elevation, when this is available.

The following data-manipulation options are available:

• Disable calculation of corrected elevation when new activities are imported, using the "Edit/Preferences..." menu entry. Do this if corrected elevation is not working as expected for you (although reporting an issue would be appreciated).

• Clear the elevation for a single activity, using the "Activity/Clear Corrected Elevation..." menu entry. Do this if the corrected elevation or grade information looks incorrect the activity.

• Refresh the corrected elevation for a single activity by selecting the "Activity/Fixup Elevation..." menu entry. This is useful to re-create the previously cleared corrected elevation data, or, if you started using a new training route, and older sessions on that route did not have enough points to provide a good corrected data.

• Refresh the corrected elevation for all sessions from the "Tools/Fixup Elevation..." menu. This will take a very long time of you have a lot of activities in the database.