diff --git a/lidar_pipeline/visualizations.py b/lidar_pipeline/visualizations.py
index 0b16e2c..596a0e9 100644
--- a/lidar_pipeline/visualizations.py
+++ b/lidar_pipeline/visualizations.py
@@ -470,7 +470,8 @@ def generate_hillshade(dem_file, basename, vis_dir, resolution, shared=None):
         else:
             dem_np, transform, crs = _read_dem(dem_file)
             dem = to_gpu(dem_np)
-            dy, dx = xp.gradient(dem)
+            # Espacement = résolution (m/px) : sans lui la pente est fausse
+            dy, dx = xp.gradient(dem, float(resolution) if resolution else 1.0)
             slope = xp.arctan(xp.sqrt(dx**2 + dy**2))
             aspect = xp.arctan2(dy, dx)
             sin_slope = xp.sin(slope)
@@ -532,7 +533,8 @@ def generate_slope(dem_file, basename, vis_dir, resolution, shared=None):
         else:
             dem_np, transform, crs = _read_dem(dem_file)
             dem = to_gpu(dem_np)
-            dy, dx = xp.gradient(dem)
+            # Espacement = résolution (m/px) : sans lui la pente est fausse
+            dy, dx = xp.gradient(dem, float(resolution) if resolution else 1.0)
             slope = xp.arctan(xp.sqrt(dx**2 + dy**2)) * 180 / xp.pi
             nan_mask = np.isnan(dem_np)
         _save_tif(output, to_cpu(slope) if _gpu_mod.HAS_GPU else slope, transform, crs, nan_mask=nan_mask)
@@ -567,7 +569,8 @@ def generate_aspect(dem_file, basename, vis_dir, resolution, shared=None):
         else:
             dem_np, transform, crs = _read_dem(dem_file)
             dem = to_gpu(dem_np)
-            dy, dx = xp.gradient(dem)
+            # Espacement = résolution (m/px) : sans lui la pente est fausse
+            dy, dx = xp.gradient(dem, float(resolution) if resolution else 1.0)
             nan_mask = np.isnan(dem_np)
         aspect = xp.arctan2(dy, dx) * 180 / xp.pi
         aspect = xp.mod(aspect, 360)