geopandas_rasterio_sample.ipynb.txt

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    "\n",
    "# Using GeoPandas with Rasterio to sample point data\n",
    "\n",
    "This example shows how to use GeoPandas with Rasterio.  [Rasterio](https://rasterio.readthedocs.io/en/latest/index.html) is a package for reading and writing raster data.\n",
    "\n",
    "In this example a set of vector points is used to sample raster data at those points.\n",
    "\n",
    "The raster data used is Copernicus Sentinel data 2018 for Sentinel data.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import geopandas\n",
    "import rasterio\n",
    "import matplotlib.pyplot as plt\n",
    "from shapely.geometry import Point"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Create example vector data\n",
    "=============================\n",
    "\n",
    "Generate a geodataframe from a set of points\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "# Create sampling points\n",
    "points = [Point(625466, 5621289), Point(626082, 5621627), Point(627116, 5621680), Point(625095, 5622358)]\n",
    "gdf = geopandas.GeoDataFrame([1, 2, 3, 4], geometry=points, crs=32630)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "The ``GeoDataFrame`` looks like this:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "gdf.head()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Open the raster data\n",
    "=============================\n",
    "\n",
    "Use ``rasterio`` to open the raster data to be sampled"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "src = rasterio.open('s2a_l2a_fishbourne.tif')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Let's see the raster data with the point data overlaid.\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "tags": [
     "nbsphinx-thumbnail"
    ]
   },
   "outputs": [],
   "source": [
    "from rasterio.plot import show\n",
    "\n",
    "fig, ax = plt.subplots()\n",
    "\n",
    "# transform rasterio plot to real world coords\n",
    "extent=[src.bounds[0], src.bounds[2], src.bounds[1], src.bounds[3]]\n",
    "ax = rasterio.plot.show(src, extent=extent, ax=ax, cmap='pink')\n",
    "\n",
    "gdf.plot(ax=ax)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Sampling the data\n",
    "===============\n",
    "Rasterio requires a list of the coordinates in x,y format rather than as the points that are in the geomentry column.\n",
    "\n",
    "This can be achieved using the code below"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "coord_list = [(x,y) for x,y in zip(gdf['geometry'].x , gdf['geometry'].y)]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Carry out the sampling of the data and store the results in a new column called `value`.  Note that if the image has more than one band, a value is returned for each band."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "gdf['value'] = [x for x in src.sample(coord_list)]\n",
    "gdf.head()"
   ]
  }
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