Demo for calculating raster zonal statistics for many zones in parallel using Google Earth Engine.

ee_zonal_stats_demo.ipynb

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  "metadata": {
    "colab": {
      "name": "ee_zonal_stats_demo.ipynb",
      "provenance": [],
      "include_colab_link": true
    },
    "kernelspec": {
      "name": "python3",
      "display_name": "Python 3"
    },
    "language_info": {
      "name": "python"
    }
  },
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "view-in-github",
        "colab_type": "text"
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      "source": [
        "<a href=\"https://colab.research.google.com/gist/jdbcode/2117c512f2a8bd8c2a20555fba90a61b/ee_zonal_stats_demo.ipynb\" target=\"_parent\"><img src=\"https://colab.research.google.com/assets/colab-badge.svg\" alt=\"Open In Colab\"/></a>"
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "# Earth Engine setup.\n",
        "import ee\n",
        "ee.Authenticate()\n",
        "ee.Initialize()"
      ],
      "metadata": {
        "id": "3Cb8cjxESqO3"
      },
      "execution_count": null,
      "outputs": []
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "id": "0M6v43DjRI9p"
      },
      "outputs": [],
      "source": [
        "# Import raster image.\n",
        "dem = ee.Image('NASA/NASADEM_HGT/001')\n",
        "\n",
        "# Import feature collection of watersheds (zones) (50 zones for demo).\n",
        "zones = ee.FeatureCollection(\"WWF/HydroSHEDS/v1/Basins/hybas_9\").limit(50)\n",
        "\n",
        "# Calculate zonal stats (mean and median).\n",
        "stats = dem.reduceRegions(**{\n",
        "  \"collection\": zones,\n",
        "  \"reducer\": ee.Reducer.mean().combine(ee.Reducer.median(), None, True),\n",
        "  \"scale\": 30\n",
        "})\n",
        "\n",
        "# Export the result as a CSV file to Google Drive.\n",
        "task = ee.batch.Export.table.toDrive(**{\n",
        "  \"collection\": stats,\n",
        "  \"description\": \"ee_demo_zonal_stats\",\n",
        "  \"folder\": \"ee_demo\",\n",
        "  \"fileNamePrefix\": \"ee_demo_zonal_stats\",\n",
        "  \"fileFormat\": \"CSV\",\n",
        "  \"selectors\": [\"HYBAS_ID\", \"elevation_mean\", \"elevation_median\"]\n",
        "})\n",
        "task.start()"
      ]
    }
  ]
}