I think its done

ConsoleApp/Sim/DetectionHead.cs

@@ -24,6 +24,6 @@ namespace ConsoleApp.Sim
         public static List<Cell> GetCoveredCells(
             ISquareMap squareMap,
             Cell centerCell,
-            int detectorRadius) => squareMap.GetRange(centerCell, detectorRadius);
+            int detectorRadius) => squareMap.GetRange(centerCell, detectorRadius * 2 - detectorRadius%2);
     }
 }

ConsoleApp/Sim/IVehicle.cs

@@ -10,6 +10,6 @@ namespace ConsoleApp.Sim
         int TurnRadius { get; }
         int DetectorRadius { get;}
         Coordinate2D CurrentHexCell { get; set; }
-        ICell CurrentSquareCell { get; set; }
+        Cell CurrentSquareCell { get; set; }
     }
 }

ConsoleApp/Sim/Vehicle.cs

@@ -11,7 +11,7 @@ namespace ConsoleApp.Sim
         public int TurnRadius { get; }
         public int DetectorRadius { get;}
         public HexCore.Coordinate2D CurrentHexCell { get; set; }
-        public ICell CurrentSquareCell { get; set; }
+        public Cell CurrentSquareCell { get; set; }
         
         
 

ConsoleApp/Sim/VehicleConfiguration.json

@@ -1,5 +1,5 @@
 {
   "Length": 1,
   "Width": 1,
-  "DetectorRadius": 1
+  "DetectorRadius": 2
 }