Spalt Maps Problem....

hi guys i am trying to set textures on terrian by spalt maps but it dsnt work i am using the simple code to set the texures but it returning null value every time i test it with diffrent ways can u guys help me in solving this problem here is the code i am using plz help... thanks

     SplatPrototype[] terrainTexture = new SplatPrototype[4];
     terrainTexture[0] = new SplatPrototype();
     terrainTexture[0].texture = (Texture2D)Resources.Load("TEX/GLO_TIL_BRICK_439_MAP_L9_2013_1");
     terrainTexture[0].tileOffset = new Vector2(0, 0);
     terrainTexture[0].tileSize = new Vector2(15, 15);
         Debug.Log ( terrainTexture[0]);
      Debug.Log ( tex1);
      
      
     terrainTexture[1] = new SplatPrototype();
     terrainTexture[1].texture =(Texture2D)Resources.Load("TEX/GLO_TIL_BRICK_656_MAP_L9_2013_1");
     terrainTexture[1].tileOffset = new Vector2(0, 0);
     terrainTexture[1].tileSize = new Vector2(15, 15);
      
     terrainTexture[2] = new SplatPrototype();
     terrainTexture[2].texture =(Texture2D)Resources.Load("TEX/GLO_TIL_FINERY_180_MAP_L9_2013_1");
     terrainTexture[2].tileOffset = new Vector2(0, 0);
     terrainTexture[2].tileSize = new Vector2(15, 15);
      
      
     terrainTexture[3] = new SplatPrototype();
     terrainTexture[3].texture =(Texture2D)Resources.Load("TEX/GLO_TIL_GRASS_002_MAP_L9_2013_1");
     terrainTexture[3].tileOffset = new Vector2(0, 0);
     terrainTexture[3].tileSize = new Vector2(15, 15);
      
      
     terrainData.splatPrototypes = terrainTexture;
      
      
     float[,,] map = new float[terrainData.heightmapWidth-1,terrainData.heightmapHeight-1, 4]; // needs to be 1
     // For each point on the alphamap...
      
     for (int y = 0; y < terrainData.heightmapWidth-1; y++)
     {
     for (int x = 0; x < terrainData.heightmapHeight-1; x++)
     {
     if(terrainData.GetHeight(y,x)<10)
     map[x, y, 0] = 1.0f;
     else if(terrainData.GetHeight(y,x)<20)
     {
     map[x, y, 0] = 0.5f;
     map[x, y, 1] = 0.5f;
     }
     else if(terrainData.GetHeight(y,x)<30)
     map[x, y, 1] = 1.0f;
     else if(terrainData.GetHeight(y,x)<40)
     {
     map[x, y, 1] = 0.5f;
     map[x, y, 2] = 0.5f;
     }
     else if(terrainData.GetHeight(y,x)<50)
     map[x, y, 2] = 1.0f;
     else if(terrainData.GetHeight(y,x)<60)
     {
     map[x, y, 2] = 0.5f;
     map[x, y, 3] = 0.5f;
 //    print (terrainData.GetHeight(y,x));
     }
     else if(terrainData.GetHeight(y,x)<70)
     map[x, y, 3] = 1.0f;
     else if(terrainData.GetHeight(y,x)<80)
     {
     map[x, y, 3] = 0.5f;
     map[x, y, 4] = 0.5f;
 //    print (terrainData.GetHeight(y,x));
     }
     else if(terrainData.GetHeight(y,x)<90)
     map[x, y, 4] = 1.0f;
     }
     }
     terrainData.SetAlphamaps(0, 0, map);
     }