Trying calculate Zonal_stats using mosaic and H3

[Jaynab_1]

I am trying to calculate Zonal_stats for raster data using mosaic and H3. Created dataframe from geometry data to H3 index. While previously I was calculating Zonal_stats using rasterio, tif file, geometry data in python which is slow. Now want to explore mosaic and H3 index. In my case, I need to calculate Zonal_stats for each geometry point. Any idea if this function exists in Mosaic?

[Kaniz_Fatma]

Hi @Jaynab_1, Let’s explore how you can calculate zonal statistics using Mosaic and H3. While Mosaic itself doesn’t directly provide a built-in function for zonal statistics, we can leverage other tools and libraries to achieve this.

1. Zonal Statistics with Mosaic and H3:

   • H3 is a powerful hexagonal grid system that can be used for spatial indexing and aggregation.
   • To calculate zonal statistics for each geometry point using H3, follow these steps:
     1. Convert Geometry to H3 Index:
        • You’ve already created a DataFrame from your geometry data to H3 indexes. Ensure that each geometry point is associated with a specific H3 index.
     2. Rasterize H3 Hexagons:
        • Convert the H3 hexagons to a raster format (e.g., GeoTIFF or other supported formats). Each hexagon will represent a zone.
     3. Calculate Zonal Statistics:
        • Overlay the rasterized H3 hexagons with your raster data (e.g., using Mosaic).
        • Extract cell values from the raster for each hexagon zone.
        • Compute statistics (e.g., mean, sum, etc.) for each zone.
     4. Output:
        • You’ll obtain zonal statistics for each H3 hexagon zone.

2. Existing Tools and Libraries:

   • While Mosaic doesn’t directly provide a zonal statistics function, you can use other Python libraries:
     • rasterio: You mentioned using it previously. It’s a great choice for reading and writing raster data.
     • rasterstats: A Python module that specializes in summarizing geospatial raster datasets based on vector geometries. It includes functions for zonal statistics and interpolated point queries¹.
     • ArcGIS Pro (Spatial Analyst): If you have access to ArcGIS Pro, it provides tools like “Zonal Statis...².
     • QGIS: QGIS also offers zonal statistics tools that you can use in combination with H3 indexes.

3. Example Workflow:

   • Here’s a simplified example using rasterstats:
     • Install the library: pip install rasterstats.
     • Load your raster data and H3 hexagons.
     • Use rasterstats.zonal_stats to compute statistics for each H3 zone.
     • Output the results (e.g., mean, sum, etc.) for further analysis.

Remember to adjust the workflow based on your specific data and requirements. If you need further assistance or have additional questions, feel free to ask! 🌟