The GPSResults program can be used to calculate and evaluate the track-velocities from measured GPS-data. First of all the data (trackpoints) have to be read from your GPS, transferred to your computer, and saved as gpx-file. The trackpoints can be downloaded from the GPS directly using GPSResults (only for Garmin Geko 201, Foretrex 101 oder Foretrex 201: File - Download Trackpoints from GPS...: select COM-Port, press Read Trackpoints and finally save as gpx-file). For the Garmin eTrex Legend C with USB interface there is also the option USB for a much faster download od the trackpoints directly via the USB-port. Don´t use this option if you use an USB-serial-adaptor! GPS-data, leading to more accurate and often slightly improved results.
When Lin. Interpolation is switched off the track- or time-segments will be added conventionally until the selected value is reached. For example with 2sec measuring intervals the average of 6sec-segments will be used for the 5sec measure. The same is true for e.g. the 500m selection where the average over at least 500m will be used (the really travelled distance is displayed as second number in best five list).
When Lin. Interpolation is switched on, the average speed of the exact track- or time-lengths is computed by linear interpolation of the first or last tracksegment, depending on which piece was the slower one. Thus, only as much as necessary of the slower interval is used. In most cases this leads to slightly better average speeds. Only in cases where e.g. the first and the last sections were faster then the middle sections, the conventional method gives better, but more inaccurate averaged results, since then the average of the longer distance is better than the average of the really wanted distance.
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