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feat(route-builder): densify + elevate off-trail segments

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With "snap to route" off, every waypoint pair shipped as a 2-point
linear segment with no `<ele>` anywhere — the page only enriched
elevations inside the snap path. The resulting GPX had a flat
altitude profile and the build script's gain/loss/min/max metrics
came out all zero.

Two changes:

* New `densifyLinearSegments` (default 25 m, matches Swisstopo's
  coarsest DTM) walks every 2-point segment and seeds intermediate
  vertices along the great circle. Snapped segments (already many
  points from BRouter) are left alone.
* Page reactor now runs the same Swisstopo elevation enrichment in
  the autoSnap-off path, so the GPX carries per-trkpt `<ele>` even
  for fully manual / cross-country routes.

Elevation source unchanged: Swisstopo profile.json (COMB → DTM2 →
DTM25 fallback) is already the highest-resolution provider for our
Swiss-coverage hikes; no point swapping.

Also unifies the snap-path's inline enrichment call into the same
helper so there's one elevation code path instead of two.
This commit is contained in:
Alexander Bocken
2026-05-19 10:40:24 +02:00
parent a1aa722512
commit e3ccd96c7b
3 changed files with 103 additions and 22 deletions
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src/routes/hikes/route-builder/+page.svelte
+42 -21
View File
@@ -10,13 +10,39 @@
setRoutedSegments,
setElevations,
clearDraft,
reconcileSegments
reconcileSegments,
densifyLinearSegments
} from '$lib/components/hikes/route-builder/builderStore.svelte';
let busy = $state(false);
let error = $state<string | null>(null);
let routeRequestId = 0;
/**
* Pull elevations from Swisstopo for every point of the current
* `routedSegments` that lacks one, then fold the values back into the
* segment arrays. Shared by the snap path (where BRouter sometimes
* doesn't return elevations) and the manual / off-trail path (where
* we densify a straight line then need its profile).
*
* Returns silently if every point already has an altitude — handy when
* BRouter snapped the route and embedded elevations inline.
*/
async function enrichMissingElevations(reqId: number): Promise<void> {
const flat = builder.routedSegments.flat();
if (flat.length === 0) return;
if (!flat.some((p) => typeof p[2] !== 'number')) return;
const elevRes = await fetch('/api/hikes/route-builder/elevation', {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify({ coordinates: flat.map((p) => [p[0], p[1]]) })
});
if (reqId !== routeRequestId) return;
if (!elevRes.ok) return;
const { elevations } = (await elevRes.json()) as { elevations: (number | null)[] };
setElevations(elevations);
}
async function snapToRoute() {
const placed = builder.waypoints.filter((w) => !w.unplaced);
if (placed.length < 2) {
@@ -46,22 +72,9 @@
};
if (reqId !== routeRequestId) return;
setRoutedSegments(data.segments);
// If routing didn't return elevations, enrich via Swisstopo.
const flat = data.segments.flat();
const needsElevation = flat.some((p) => typeof p[2] !== 'number');
if (needsElevation) {
const elevRes = await fetch('/api/hikes/route-builder/elevation', {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify({ coordinates: flat.map((p) => [p[0], p[1]]) })
});
if (reqId !== routeRequestId) return;
if (elevRes.ok) {
const elevData = (await elevRes.json()) as { elevations: (number | null)[] };
setElevations(elevData.elevations);
}
}
// BRouter usually embeds elevations inline; OSRM / linear
// fallbacks don't. Single helper handles both cases.
await enrichMissingElevations(reqId);
} catch (err) {
if (reqId !== routeRequestId) return;
error = (err as Error).message;
@@ -95,10 +108,18 @@
if (builder.autoSnap) {
snapDebounce = setTimeout(() => snapToRoute(), 250);
} else {
// Keep whatever was already snapped. Cancel any in-flight request so
// a late response doesn't overwrite the linear placeholders we just
// reconciled.
routeRequestId++;
// Manual / off-trail mode: keep already-snapped pairs intact
// (reconcileSegments preserved them); but for any fresh
// two-point linear placeholder, densify to ~25 m spacing and
// pull a Swisstopo elevation profile so the GPX carries
// per-trkpt `<ele>` even when the user chose not to snap.
// Cancel any in-flight snap request so a late response can't
// overwrite what we're about to densify.
const reqId = ++routeRequestId;
snapDebounce = setTimeout(async () => {
densifyLinearSegments(25);
await enrichMissingElevations(reqId);
}, 250);
}
});
});