added linear slider

server/core/elevation.py

@@ -371,6 +371,7 @@ def _offset_m(lat: float, lon: float, north_m: float, east_m: float) -> tuple[fl
 
 
 _MAX_GRID_POINTS = 2500
+_MAX_GRID_POINTS_FINE = 12000
 
 
 def _auto_step_m(radius_m: float) -> float:
@@ -401,11 +402,15 @@ def _sample_circular_grid(
     return cells
 
 
-def _resolve_grid_step(lat: float, lon: float, radius_m: float, step_m: float) -> float:
+def _resolve_grid_step(
+    lat: float, lon: float, radius_m: float, step_m: float
+) -> float:
     if step_m <= 0:
         step_m = _auto_step_m(radius_m)
-    step_m = max(5.0, min(float(step_m), 100.0))
-    while len(_sample_circular_grid(lat, lon, radius_m, step_m)) > _MAX_GRID_POINTS:
+    min_step = 1.0 if radius_m <= 100.0 else 5.0
+    step_m = max(min_step, min(float(step_m), 100.0))
+    max_points = _MAX_GRID_POINTS_FINE if radius_m <= 100.0 and step_m <= 1.0 else _MAX_GRID_POINTS
+    while len(_sample_circular_grid(lat, lon, radius_m, step_m)) > max_points:
         step_m = math.ceil(step_m * 1.25)
         if step_m >= radius_m:
             break
@@ -427,7 +432,7 @@ def build_elevation_grid(
             "elevation_url": ELEVATION_API_URL,
         }
 
-    radius_m = max(100.0, min(float(radius_m), 500.0))
+    radius_m = max(50.0, min(float(radius_m), 500.0))
     step_m = _resolve_grid_step(lat, lon, radius_m, step_m)
 
     center_elev = fetch_elevation_m(lat, lon)