@mytec: iter3.10 start, baseline rc ready

backend/app/services/coverage_service.py

@@ -526,19 +526,33 @@ class CoverageService:
             progress_fn("Loading terrain", 0.25)
             await asyncio.sleep(0)
         t_terrain = time.time()
+
+        # Check for missing tiles before attempting download
+        radius_km = settings.radius / 1000.0
+        missing_tiles = self.terrain.get_missing_tiles(site.lat, site.lon, radius_km)
+        if missing_tiles:
+            _clog(f"⚠ Missing terrain tiles: {missing_tiles} - will attempt download")
+
         tile_names = await self.terrain.ensure_tiles_for_bbox(
             min_lat, min_lon, max_lat, max_lon
         )
         for tn in tile_names:
             self.terrain._load_tile(tn)
 
+        # Check what actually loaded
+        loaded_tiles = [tn for tn in tile_names if tn in self.terrain._tile_cache]
+        failed_tiles = [tn for tn in tile_names if tn not in self.terrain._tile_cache]
+        if failed_tiles:
+            _clog(f"⚠ TERRAIN WARNING: Failed to load tiles {failed_tiles}. "
+                  "Coverage accuracy reduced - using flat terrain for affected areas.")
+
         site_elevation = self.terrain.get_elevation_sync(site.lat, site.lon)
 
         point_elevations = {}
         for lat, lon in grid:
             point_elevations[(lat, lon)] = self.terrain.get_elevation_sync(lat, lon)
         terrain_time = time.time() - t_terrain
-        _clog(f"Tiles: {len(tile_names)}, site elev: {site_elevation:.0f}m, "
+        _clog(f"Tiles: {len(loaded_tiles)}/{len(tile_names)} loaded, site elev: {site_elevation:.0f}m, "
               f"pre-computed {len(grid)} elevations")
         _clog(f"━━━ PHASE 2 done: {terrain_time:.1f}s ━━━")