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fix: Correct globe projection orientation

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- Fix x-axis mirroring for proper globe viewing orientation
- Adjust rotation formula to use lon - rotation instead of lon + rotation
- Globe now correctly shows landmasses relative to ISS position

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
Smittix
2026-01-29 16:53:31 +00:00
parent fc3efa9655
commit b0e9b2889e
1 changed files with 9 additions and 7 deletions
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static/js/modes/sstv.js
+9 -7
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@@ -387,16 +387,18 @@ const SSTV = (function() {
* Project lat/lon to x/y on globe with rotation * Project lat/lon to x/y on globe with rotation
*/ */
function projectPoint(lat, lon, cx, cy, radius, rotation) { function projectPoint(lat, lon, cx, cy, radius, rotation) {
const lonRad = (lon + rotation) * Math.PI / 180; // Apply rotation to longitude (negative to rotate globe eastward)
const adjustedLon = lon - rotation;
const lonRad = adjustedLon * Math.PI / 180;
const latRad = lat * Math.PI / 180; const latRad = lat * Math.PI / 180;
// Check if point is on visible hemisphere // Check if point is on visible hemisphere (front of globe)
const x3d = Math.cos(latRad) * Math.sin(lonRad);
const z3d = Math.cos(latRad) * Math.cos(lonRad); const z3d = Math.cos(latRad) * Math.cos(lonRad);
if (z3d < 0) return null; // Behind globe if (z3d < 0) return null; // Behind globe
const x = cx + x3d * radius; // Project to 2D - negate x for correct left/right orientation when viewing globe
const x3d = Math.cos(latRad) * Math.sin(lonRad);
const x = cx - x3d * radius; // Negated for correct globe orientation
const y = cy - Math.sin(latRad) * radius; const y = cy - Math.sin(latRad) * radius;
return { x, y, z: z3d }; return { x, y, z: z3d };
@@ -414,8 +416,8 @@ const SSTV = (function() {
const cy = canvas.height / 2; const cy = canvas.height / 2;
const radius = Math.min(cx, cy) - 10; const radius = Math.min(cx, cy) - 10;
// Globe rotation - center on ISS longitude if available // Globe rotation - center on ISS longitude
const globeRotation = issPosition ? -issPosition.lon : 0; const globeRotation = issPosition ? issPosition.lon : 0;
// Clear canvas // Clear canvas
ctx.clearRect(0, 0, canvas.width, canvas.height); ctx.clearRect(0, 0, canvas.width, canvas.height);