Climbs: elevation profile and climb screen¶

When TrailBridge plays a GPX route, it sends the elevation profile of the road ahead all the time and announces the climbs in it (protocol, "elevation profile service"). The bike computer rates the climb and shows it on the screen RimRidgeClimb (design, §6).

Climb screen

Part	File
Wire format	`src/BikeProfileProtocol.h`
Algorithm (pure, host test)	`src/ClimbProfile.*`, `test/native_climb/climb_test.cpp`
Integration: BLE, position, settings, CLI, web, demo	`src/ClimbMonitor.*`, `BLEDevices::subscribeProfile()`
Screen	`src/ui/RimRidgeClimbCustFunc.*`, `UIFacade::updateClimb()`

What the phone sends, and what the firmware does with it¶

Rolling phone (TrailBridge since 2026-10-04, frame flag ROLLING). The profile is always sent -- on flat ground and downhill, too -- as a window of the road ahead (5 km on a 25 m raster; a climb that is further than that is cut at its foot). A climb in it is announced by the phone with its whole extent (foot and summit, remaining distance and altitude, also where they lie behind or beyond the frame): as soon as the foot is at most 500 m ahead the window runs to the summit, up to 5 km on a 25 m raster, coarser for longer climbs (up to 250 m; the 36 km Galibier from the south comes with 200 m). So

the climb does not end before its summit and category and length are those of the whole climb all the way up (test ride 2026-10-04: the category used to fall on the way, because the firmware only saw what was left of the climb in the frame),
the climb screen opens automatically only for climbs (rank at least autorank, foot closer than showahead), and goes back only after the summit was reached (summitpass behind it, then hidedelay) -- not when data runs out for a moment (off the route, a frame in flight); only after 2 minutes without any climb to show (route over, phone gone) it goes as well,
PROFILE_NONE only means "route over / off the route"; the climb the rider is on survives it.

Older phone (no flag): TrailBridge sends only the climb ahead, from the current position to the summit, in one frame, and PROFILE_NONE at the summit. The firmware then

finds the climb: the foot is the first point from which the next 100 m rise by 3 % on average. The summit is the last point before a descent of more than 30 m or before 2 km without an average gradient of 0.5 % -- or the end of the profile. A shorter flat section or a dip does not end the climb; the Galibier from the north is two climbs (descent from the Télégraphe to Valloire). TrailBridge searches with the same criteria (ElevationProfile.java there) -- the defaults of both sides belong together.
joins frames (same raster, overlapping) and keeps the part already ridden, up to 320 steps. This is only needed when a climb does not fit into one frame even on the 250 m raster.
continues a climb when the phone sends PROFILE_NONE and a new profile shortly after.

Both: the firmware

knows the position from the remaining distance in the navigation frames, advanced between two frames by the distance from the speed sensor.

Climb screen readability: the expected gradient ("NÄCHSTE 25 m") and the measured one are set in the large 48 px font; the steepest band is a full red (0xE8392A) in the profile and in the value.

Altitude figures are net: summit minus foot, summit minus rider.

Categories¶

Score = length [m] × average gradient [%] = 100 × altitude gain. This is the scale of Strava and Garmin (ClimbPro) for 4 to HC; 5 and 6 continue it downwards by halving.

Category	Score from	Altitude gain from	Example
6	2 000	20 m	400 m at 5 %
5	4 000	40 m	800 m at 5 %
4	8 000	80 m	1.6 km at 5 %
3	16 000	160 m	3 km at 5.5 %
2	32 000	320 m	5 km at 6.5 %
1	64 000	640 m	9 km at 7.5 %
HC	80 000	800 m	10 km at 8 %

Not rated (short hill, no automatic display): shorter than 300 m, flatter than 3 % on average, or less than 20 m of altitude gain.

Display¶

The screen appears by itself as soon as a rated climb is at most 300 m ahead, and returns to the main screen 5 s after its end. It only replaces the main screen; if navigation, road labels or settings are showing, it becomes the target of "back".
By hand: a tap on altitude or gradient on the main screen opens it, a swipe closes it. A climb that was swiped away does not come back by itself.
Profile colour by the gradient of the raster section (25 m, up to 250 m for long climbs): below 1 % blue, up to 4 % green, up to 7 % yellow, up to 10 % orange, red above. The part already ridden is dimmed.

Settings¶

Every value can be set individually and is stored in NVS (Climb):

climb                     state and all settings
climb cat4 9000           set
climb cat4                show (with range and meaning)
climb defaults            default values

Without USB: /debug/climb (table with input fields), /debug/climb.json, /debug/climb/set?<name>=<value>.

Name	Default	Meaning
`startgrade` / `startwindow`	3 % / 100 m	foot: average gradient over this distance
`contgrade`	0.5 %	average gradient from the summit so far with which the climb continues
`summitflat`	2000 m	flat section that ends the climb; also the distance within which a new climb continues the old one
`summitdip`	30 m	descent that ends the climb
`summitpass`	50 m	this far behind the summit the climb is over
`minlength` / `mingrade`	300 m / 3 %	not rated below
`cat6` … `cat1`, `cathc`	see above	score per category
`autoshow`	1	switch to the climb screen automatically
`autorank`	1	from which rank: 1 = category 6 … 6 = category 1, 7 = HC
`showahead`	300 m	distance to the foot at which the screen appears
`hidedelay`	5 s	wait before switching back
`lookahead`	25 m	distance for the "gradient ahead"
`band1` … `band4`	1 / 4 / 7 / 10 %	limits of the profile colours
`infocycle`	4 s	cycle of the info field (time, distance, temperature, cadence, altitude)

Trying it without a phone¶

climb demo                2 km at 6 % (default)
climb demo 4000 9         length in m, average gradient in %
climb pos 800             put the rider 800 m behind the start of the profile
climb show / climb hide   open / close the screen
climb demo off

The demo profile runs through the parser as a normal frame. The rider moves with the speed sensor (in the simulator build with sim <km/h>) or by climb pos. Frames from the phone are ignored meanwhile.

Limits¶

Only with a GPX route with altitude data played in TrailBridge. There is no profile with OsmAnd navigation.
Climbs longer than 5 km come on a coarser raster (up to 250 m); "gradient ahead" and the profile colours then average over such a section.
Above 50 km (or with a small MTU) the climb does not fit into one frame. The end of the profile then counts as a provisional summit until the next piece arrives.
Values for contgrade, summitflat and summitdip stored in NVS take precedence over new defaults (climb defaults resets them).
If the bike computer connects in the middle of a climb, the climb counts from there.