Sportractive determines the current position during a recording with the help of the GPS signal. The GPS signal also provides the current elevation however the GPS elevation is not very accurate. To address this inaccuracy Sportractive also obtains data from a more precise Digital Elevation Model. The app downloads data from the Model as needed according to the phone's location.
Sportractive always tries to calculate the elevation via the Digital Elevation Model first. If that data is not available, for example because there is no internet connection, Sportractive automatically falls back to the less accurate GPS elevation.
Climb, Descent, Elevation Threshold
To calculate climb and descent, the difference between two consecutive elevation data points is calculated. If the difference is positive it is added to the climb value, if it is negative it is added to the descent value.
To avoid every bump on an otherwise flat track being included in the climb and descent totals, Sportractive offers, from version 5, a user-adjustable elevation threshold. With this the user specifies the minimum rise or fall that will be added to the climb and descent totals.
The figure below shows how a threshold value of 5 m works in calculating the climb total for the elevation profile shown in black. It can be seen that any elevation measurement that is less than 5 m higher than a previous valid measurement is ignored (red). Only those differences that are greater than the threshold are added to the climb total (green). Thus, with a 5 m threshold the climb and descent totals are both 12 m. This can be compared with a zero threshold - the black profile - where the climb and descent totals would both be 16 m.
Unfortunately there is no standard for the elevation threshold. Each app, platform and hiking route uses its own, mostly unknown threshold. This leads to non-comparable results. Sportractive therefore offers a user-adjustable elevation threshold from version 5.
The elevation threshold can be specified in the Sportractive settings and, once set, affects all subsequent recordings. In addition, the threshold value for an existing workout can be adjusted using the Workout Editor.
Beginning with version 5 of Sportractive the elevation threshold is pre-set to 5 m or 16 feet. For workouts recorded with an older version, the threshold is 0 m or 0 feet which can be changed using the Workout Editor if necessary.