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   "source": [
    "# Coordinates_operations — CRS transformations\n",
    "\n",
    "This module provides coordinate transformation utilities between Belgian CRS:\n",
    "\n",
    "- **Lambert 72** (`EPSG:31370`) — legacy Belgian grid\n",
    "- **Lambert 2008** (`EPSG:3812`) — current Belgian grid\n",
    "- **WGS 84** (`EPSG:4326`) — lat/lon\n",
    "\n",
    "It also supports raster reprojection via GDAL."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "7ac629e9",
   "metadata": {},
   "outputs": [],
   "source": [
    "from wolfhece.Coordinates_operations import transform_coordinates\n",
    "import numpy as np"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "7893f9ac",
   "metadata": {},
   "source": [
    "## Transforming point coordinates\n",
    "\n",
    "`transform_coordinates` converts an `(n, 2)` numpy array from one EPSG to another.\n",
    "Large arrays are processed in chunks with multiprocessing."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "959f7849",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
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     "text": [
      "Lambert 2008 -> Lambert 72:\n",
      "  (710000.0, 600000.0) -> (209992.5, 99991.9)\n",
      "  (650000.0, 650000.0) -> (149997.9, 149999.4)\n"
     ]
    }
   ],
   "source": [
    "# Points in Lambert 2008 (EPSG:3812)\n",
    "pts_3812 = np.array([\n",
    "    [710000.0, 600000.0],  # approximate Liège area\n",
    "    [650000.0, 650000.0],  # approximate Brussels area\n",
    "])\n",
    "\n",
    "# Convert to Lambert 72 (EPSG:31370)\n",
    "pts_31370 = transform_coordinates(\n",
    "    pts_3812,\n",
    "    inputEPSG='EPSG:3812',\n",
    "    outputEPSG='EPSG:31370'\n",
    ")\n",
    "\n",
    "print(\"Lambert 2008 -> Lambert 72:\")\n",
    "for a, b in zip(pts_3812, pts_31370):\n",
    "    print(f\"  ({a[0]:.1f}, {a[1]:.1f}) -> ({b[0]:.1f}, {b[1]:.1f})\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "83055b63",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Lambert 2008 -> WGS 84 (lon, lat):\n",
      "  (710000.0, 600000.0) -> (5.209195, 50.207972)\n",
      "  (650000.0, 650000.0) -> (4.368720, 50.660611)\n"
     ]
    }
   ],
   "source": [
    "# Convert to WGS 84 (lat/lon)\n",
    "pts_wgs84 = transform_coordinates(\n",
    "    pts_3812,\n",
    "    inputEPSG='EPSG:3812',\n",
    "    outputEPSG='EPSG:4326'\n",
    ")\n",
    "\n",
    "print(\"Lambert 2008 -> WGS 84 (lon, lat):\")\n",
    "for a, b in zip(pts_3812, pts_wgs84):\n",
    "    print(f\"  ({a[0]:.1f}, {a[1]:.1f}) -> ({b[0]:.6f}, {b[1]:.6f})\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "e8793c47",
   "metadata": {},
   "source": [
    "## Raster reprojection\n",
    "\n",
    "`reproject_and_resample_raster` reprojects a GeoTIFF between CRS using GDAL.\n",
    "\n",
    "```python\n",
    "from wolfhece.Coordinates_operations import reproject_and_resample_raster\n",
    "from osgeo import gdal\n",
    "\n",
    "reproject_and_resample_raster(\n",
    "    input_raster_path='input_L2008.tif',\n",
    "    output_raster_path='output_L72.tif',\n",
    "    input_srs='EPSG:3812',\n",
    "    output_srs='EPSG:31370',\n",
    "    resampling_method=gdal.GRA_Bilinear,\n",
    "    xRes=1.0, yRes=1.0\n",
    ")\n",
    "```"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "6fe6ea00",
   "metadata": {},
   "source": [
    "## Summary\n",
    "\n",
    "| Function | Use case |\n",
    "|----------|----------|\n",
    "| `transform_coordinates(pts, inputEPSG, outputEPSG)` | Convert point arrays between CRS |\n",
    "| `reproject_and_resample_raster(...)` | Reproject GeoTIFF rasters via GDAL |\n",
    "\n",
    "Common Belgian EPSG codes:\n",
    "\n",
    "| EPSG | Name |\n",
    "|------|------|\n",
    "| 31370 | Belgian Lambert 72 |\n",
    "| 3812 | Belgian Lambert 2008 |\n",
    "| 4326 | WGS 84 (lat/lon) |"
   ]
  }
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