diff --git a/iface.py b/iface.py
index 45731fd..ce0f881 100644
--- a/iface.py
+++ b/iface.py
@@ -7,6 +7,7 @@ import os
 import platform
 import subprocess
 import configparser
+from math import log, tan, radians, pi, degrees, atan, sinh
 
 from downloader import CopernicusDownloader
 
@@ -220,39 +221,58 @@ class MapSelector:
             pass
 
     def xy_from_latlon(self, lat, lon):
-        lat_min, lat_max = self.config.getfloat('map','map_lat_start'), self.config.getfloat('map','map_lat_end')
-        lon_min, lon_max = self.config.getfloat('map','map_lon_start'), self.config.getfloat('map','map_lon_end')
-        # print(f"xy_from_latlon dbg coord = {lat_min}-{lat_max}-{lon_min}-{lon_max}")
-    
+        lat_min = self.config.getfloat('map', 'map_lat_start')
+        lat_max = self.config.getfloat('map', 'map_lat_end')
+        lon_min = self.config.getfloat('map', 'map_lon_start')
+        lon_max = self.config.getfloat('map', 'map_lon_end')
+
         canvas_w = self.canvas.winfo_width()
         canvas_h = self.canvas.winfo_height()
-        
-        print(f"canvas = {canvas_w} {canvas_h}  scale = {self.scale}  offset = {self.offset_x} {self.offset_y} ")
+
+        print(f"canvas = {canvas_w} {canvas_h}  scale = {self.scale}  offset = {self.offset_x} {self.offset_y}")
+
+        # Longitude (linéaire)
+        x_norm = (lon - lon_min) / (lon_max - lon_min)
+        x = x_norm * self.scale * self.original_img.width + self.offset_x
     
-        x = (lon - lon_min) / (lon_max - lon_min) * self.scale * self.original_img.width  + self.offset_x
-        y = (lat_max - lat) / (lat_max - lat_min) * self.scale * self.original_img.height + self.offset_y
-        
-        print(f" xy_from_latlon : {x} - {y}")
+        # Latitude (projection Mercator)
+        mercator_min = log(tan(pi / 4 + radians(lat_min) / 2))  # Mercator
+        mercator_max = log(tan(pi / 4 + radians(lat_max) / 2))  # Mercator
+        mercator_lat = log(tan(pi / 4 + radians(lat) / 2))      # Mercator
+
+        y_norm = (mercator_max - mercator_lat) / (mercator_max - mercator_min)
+        y = y_norm * self.scale * self.original_img.height + self.offset_y
+    
+        print(f"xy_from_latlon : {x} - {y}")
         return x, y
     
     def latlon_from_xy(self, x, y):
         # Coordonnées géographiques de la carte
-        lat_min, lat_max = self.config.getfloat('map','map_lat_start'), self.config.getfloat('map','map_lat_end')
-        lon_min, lon_max = self.config.getfloat('map','map_lon_start'), self.config.getfloat('map','map_lon_end')
+        lat_min = self.config.getfloat('map', 'map_lat_start')
+        lat_max = self.config.getfloat('map', 'map_lat_end')
+        lon_min = self.config.getfloat('map', 'map_lon_start')
+        lon_max = self.config.getfloat('map', 'map_lon_end')
+        
         print(f"latlon_from_xy dbg coord = {lat_min}-{lat_max}-{lon_min}-{lon_max}")
         
-        
-        # Calculer la position relative sur l'image
+        # Calculer la position relative dans l’image (sans offset/zoom)
         img_x = (x - self.offset_x) / self.scale
         img_y = (y - self.offset_y) / self.scale
     
-        # Vérifier si le clic est dans l'image affichée
         if 0 <= img_x <= self.original_img.width and 0 <= img_y <= self.original_img.height:
             rel_x = img_x / self.original_img.width
             rel_y = img_y / self.original_img.height
-            lat = lat_max - rel_y * (lat_max - lat_min)
+    
+            # Longitude : linéaire
             lon = lon_min + rel_x * (lon_max - lon_min)
-            print(f" latlon_from_xy : {lat} - {lon}")
+    
+            # Latitude : projection inverse de Mercator
+            merc_min = log(tan(pi / 4 + radians(lat_min) / 2))  # Mercator
+            merc_max = log(tan(pi / 4 + radians(lat_max) / 2))  # Mercator
+            merc_y = merc_max - rel_y * (merc_max - merc_min)
+            lat = degrees(atan(sinh(merc_y)))                   # Mercator Inverse
+    
+            print(f"latlon_from_xy : {lat} - {lon}")
             return lat, lon
         else:
             return None, None  # En dehors de l'image
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..c6e1cc9
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,2 @@
+pillow
+copernicusmarine