Name: Power Zone Gauge Index
Author: droidgren

A power zone gauge that fills the space it is given — a full ring, a half ring, or a bar — and shows your zone as a decimal index, a wattage, or a percentage of your threshold.

This project is completely free and built for the community. If you find it useful, buying me a coffee helps: https://ko-fi.com/droidgren

Power Zone Gauge Index shows how hard you are working at a glance, in the zones your sport actually uses: seven zones off FTP for cycling, five off threshold power for running.

Cycling, as a percentage of FTP: zone 1 runs to 55%, then 75, 90, 105, 120 and 150%, with zone 7 above that. Running, as a percentage of threshold power: zone 1 starts at 65%, then 80, 90, 100 and 115%, with zone 5 above that.

It also shows how far through that zone you are: 3.5 means halfway between the bottom and the top of zone 3, detail a plain zone number hides.

Crank power is noisy, so the field smooths it three seconds under the cycling model, the convention your head unit uses. Running power the watch has already smoothed, and is taken as it comes.

It fits the layout you use, picking a shape from the space the activity profile gives it:
• A full-screen field on a round watch draws a 270° ring, opening at the bottom.

• A half-height field draws a 180° half ring concentric with the display: an arch in the upper slot, a bowl in the lower one.

• The outer rows of a three- or four-field layout follow the display curve as a shallow arc.

• A middle row, or a quadrant of a round watch, draws a flat segmented bar.

• On an Edge and the other rectangular devices the shape of the space decides alone: a tall field draws the ring, a short one the bar.

Ten settings, all in the Garmin Connect app.

• Zone Model — Auto (default) follows your activity profile; Cycling and Running pin it, worth doing on an Edge, where the reported profile is often generic.

• Threshold Source — Garmin profile (default) takes the zones, or failing those the FTP, from your profile on the newer devices that expose them, and the two settings below everywhere else. App settings never asks the profile.

• Cycling FTP and Running threshold power — the watts the zones are built from, and the only settings you have to touch.

• Power Averaging — Auto (default) smooths three seconds under the cycling model and takes the instant reading under the running one. Instant, 3, 10 or 30 seconds pin one window everywhere.

• Gauge Design — Auto (default) picks the shape as above. Gauge asks for the arc wherever one is readable. Bar keeps the flat bar everywhere.

• Displayed Value — Zone index (default), for example 3.5; Power, for example 245 W; or Percent of threshold, for example 92%.

Gauge Zones — how much of your zone range the gauge covers:
• Current (default): only the zone you are in, rescaled each time you change zone. If zone 3 is 151–180 W the gauge runs 151 to 180 in green; cross into zone 4 and it restarts near empty in yellow.
• All zones: every zone as fixed coloured segments, with a marker showing where you are. The zone you are in is drawn at the full thickness of the band and the rest a little shallower. AMOLED watches use Garmin's own zone colours; transflective displays a palette picked for their narrower range.
• Top zones: just the hard end of the scale — 5 to 7 for cycling, 4 to 5 for running — for interval and threshold work.

Color value by Zone — off by default, drawing the number in white or black. Turned on, it takes the colour of the zone you are in.

Count values below Zone 1 (Zone 0) as Zone 1 — running zone 1 starts at 65% of threshold, and anything under has no zone. On by default, that range counts as zone 1 and the gauge tracks it, the index reading 0.1 to 1.9. Cycling zone 1 already starts at zero. Zero watts is always zone 0: coasting is not an easy effort.

Recorded to your FIT file. The decimal zone index is written as a developer field called Power Zone Index, whichever value you display, for analysis in Garmin Connect or any FIT tool.