GearPred

GearPred is a data field for cycling for displaying, in real time, the combination of front chain ring and rear cog that is being used. GearPred predicts the gear combination from speed and cadence and requires an active connection to sensors for both speed and cadence. GearPred was developed for road cycling. ** Display ** The primary display for GearPred is the predicted gear combination as “front gear – rear gear”, e.g. 50 – 21. If coasting or stopped, GearPred will display the last predicted gear combination with an asterisk, e.g. 50 – 21*. At startup, or if there is no motion for an extended time, GearPred will display “--“. GearPred will transiently display messages indicating the status of the auto-calibration (below), where [number] is the value of standard error [SE] parameter: “Full calib. SE: [number]” -- calibration is complete with SE. “Interim calib. SE: [number]-- calibration is in progress with interim SE. “Calibrating” -- calibration in progress at startup. “Calibrated” -- calibration complete at startup. “Using default parameters” -- auto-calibration is off at startup (and parameter values reset to defaults). GearPred will also display error messages related to problems with the settings. ** Output Field ** GearPred writes the estimated gear ratio to the “.fit” file recording of the activity (i.e. ride). View in the Garmin Connect mobile app or web utility. ** Settings ** Enter the settings from the Settings menu via the Garmin Connect app on a mobile phone or Garmin Express on a laptop/desktop. If the latter, look for GearPred under “data fields” and click on the “…” symbol to enter settings. 1. Number of teeth on front chain rings and rear cogs You must enter the number of teeth on the front chain rings and rear cogs. In the Settings menu, these are grouped under the headings “Front gears” and “Rear gears”. 2. Wheel circumference (meters) Similarly, you must enter circumference in meters for the wheel that has the speed sensor. This information is on the web for most combinations of rim size and tire. Alternatively, it can be measured directly. 3. Stability v. response Estimating the gear ratio from speed and cadence is intrinsically unstable. GearPred stabilizes the estimate by averaging over time. Averaging over longer times increases stability but also slows the response for predicting a new gear combination. GearPred has preset options to handle this tradeoff: low stability/fast response, medium stability/medium response, high stability/slow response. The optimal choice will depend on whether auto-calibration is complete or is being used at all. 4. Auto-calibration? (yes/no) GearPred uses auto-calibration to learn parameters that improve its performance. - Using auto-calibration o Switch the auto-calibration toggle to “on” and use the data field. Full auto-calibration may require an hour or more. If auto-calibration is not complete in a single ride, GearPred will store interim information, and pick up where it left off on the next ride(s) until auto-calibration is complete. GearPred will display messages as calibration progresses (above). To continue to use calibrated parameters, LEAVE auto-calibration in the “on” position. If you switch the auto-calibration to “off”, the parameters will be reset to the defaults. - Resetting the calibration o The calibration can be reset as needed, e.g. if you change gearing, switch the computer to a different bike, etc.). To reset, switch the auto-correlation toggle to “off”, use GearPred for a very short ride, e.g. 15 seconds, and then switch the auto-correlation toggle back to “on”. Auto-calibration will then start from the beginning. - De-activating calibration (i.e. the using defaults) o GearPred will use default parameters (and reset the calibration) when the auto-calibration toggle is “off”.

v. 0.9.0 initial release, May 31, 2023