Background: You can only modify workout courses for activities while you are about to import them. Once they are within the diary, it's not possible anymore to alter them.
Solution: Use the track-point inspector panel to modify the activities track before you import the activity.
There are two techniques you can now use to correct the data to be imported before you actually import them. In both cases, first open the track-point inspector panel in the bottom toolbar:
1) Select the range you want to remove. In the track-point inspector panel select the 'trim selection' command. This will remove all data points from the selection up to the nearest edge.
2) Select one data point, e.g. the first datapoint of the presumable next workout. In the track-point inspector panel, select the 'split at selection' command. This will remove the selected data point and create two new entries for either side of the selection.
Reference: Please also see Tutorial > Import Activities
Explanation: TrailRunner can display the maximum speed value from either the imported workout data (if available) or can calculate the value by an analysis of your workout data.
On statistical aggregates
If your GPS Device has lost its signal and re-catches it, the recoded course may contain errors. This error may lead to unrealistic values as such signal jumps may assume you where moving faster that light. Therefore TrailRunner uses a low-pass filter of roughly 90% and takes the highest value within the result as your maximum speed. To turn this off, uncheck the calculate statistical aggregates option.
On split intervals
The horizontal interval size slider controls the size of interval splits.
The intervals are being displayed as white lines in the graph, each containing a white circle on the value that was most common within this interval.
In addition the lowest values and the highest values within this interval are being displayed as a dot bordered gray region.
The overall maximum speed of an activity is the maximum speed from all these split intervals.
As this is a statistical calculation, the values may vary when you change the size of the split intervals. The bigger the intervals, any filtering becomes stronger.
Background: Other applications display the raw data of a device. This makes the graph unreadable. The philosophy of TrailRunner instead is to display the overall trend and development of your workout session.
Approach: TrailRunner has an auto split feature where the workout is being sliced into fixed distance intervals. For each interval the statistical median value is being calculated and one data point reflecting this value is then being used as a representative. As the location of the representative can be somewhere in-between the first interval, the graph might appear to be indented. Furthermore if representatives in adjacent intervals fall onto a straight line, only the edges representatives are being drawn and the connection line depicts the trend development.
Details: The auto split feature uses the following distance intervals. By the time of this writing it’s 250 m for workouts shorter than 10 km, then 500m up to 20 km, 1000 m up to 50 km and 10000 m from there on. A route with 42 km would then have 5 intervals.
Example: Below the identical workout in Garmin Training Center (upper image) and TrailRunner (lower image)
It’s rather obvious that the speed Graph in Garmin Training Center is full of noise and false signals. TrailRunner filters this out and gives you the statistical trend (blue line) for each interval (white circle within each interval separated by a white vertical line)
The thinner line around the blue line depicts the value range, so you still can make up that within the interval there was a great spread of values, but most of the time you stayed near the value depicted by the thick line.
BTW please note that the Garmin speed graph is upside down, so slower is a value near the top and faster is a value near the end. TrailRunner uses a the natural, mirrored display approach, where “better” is on top.