GIS MCP Server

Instructions

Implementation Reference

• src/gis_mcp/rasterio_functions.py:1092-1172 (handler)

  The core handler function for the 'raster_algebra' tool. It takes two raster paths, a band index, an operation ('add' or 'subtract'), and a destination path. Automatically aligns the rasters if CRS, transform, or shape differ, performs the operation on the specified bands, and writes the result to the output file.

  def raster_algebra(
      raster1: str,
      raster2: str,
      band_index: int,
      operation: str,  # User selects "add" or "subtract"
      destination: str
  ) -> Dict[str, Any]:
      """
      Perform algebraic operations (addition or subtraction) on two raster bands, 
      handling alignment issues automatically.
  
      Parameters:
      - raster1:     Path to the first raster (.tif).
      - raster2:     Path to the second raster (.tif).
      - band_index:  Index of the band to process (1-based index).
      - operation:   Either "add" or "subtract" to specify the calculation.
      - destination: Path to save the result as a new raster.
  
      The function aligns rasters if needed, applies the selected operation, and saves the result.
      """
      try:
          import rasterio
          import numpy as np
          from rasterio.warp import reproject, calculate_default_transform, Resampling
  
          # Expand file paths
          r1 = os.path.expanduser(raster1.replace("`", ""))
          r2 = os.path.expanduser(raster2.replace("`", ""))
          dst = os.path.expanduser(destination.replace("`", ""))
  
          # Open the raster files
          with rasterio.open(r1) as src1, rasterio.open(r2) as src2:
              # Ensure alignment of rasters
              if src1.crs != src2.crs or src1.transform != src2.transform or src1.shape != src2.shape:
                  transform, width, height = calculate_default_transform(
                      src2.crs, src1.crs, src2.width, src2.height, *src2.bounds
                  )
                  aligned_data = np.zeros((height, width), dtype="float32")
                  reproject(
                      source=src2.read(band_index),
                      destination=aligned_data,
                      src_transform=src2.transform,
                      src_crs=src2.crs,
                      dst_transform=transform,
                      dst_crs=src1.crs,
                      resampling=Resampling.bilinear
                  )
                  band2 = aligned_data
              else:
                  band2 = src2.read(band_index).astype("float32")
  
              band1 = src1.read(band_index).astype("float32")
  
              # Perform the selected operation
              if operation.lower() == "add":
                  result = band1 + band2
              elif operation.lower() == "subtract":
                  result = band1 - band2
              else:
                  raise ValueError("Invalid operation. Use 'add' or 'subtract'.")
  
              # Prepare output raster metadata
              profile = src1.profile.copy()
              profile.update(dtype="float32", count=1)
  
          # Ensure the output directory exists
          os.makedirs(os.path.dirname(dst) or ".", exist_ok=True)
  
          # Save the result to a new raster file
          with rasterio.open(dst, "w", **profile) as dstfile:
              dstfile.write(result, 1)
  
          return {
              "status": "success",
              "destination": dst,
              "message": f"Raster operation '{operation}' completed and saved."
          }
  
      except Exception as e:
          raise ValueError(f"Failed to perform raster operation: {e}")

• src/gis_mcp/rasterio_functions.py:11-35 (registration)

  Resource endpoint listing 'raster_algebra' as an available rasterio operation, which serves as a discovery mechanism for the tool.

  @gis_mcp.resource("gis://operation/rasterio")
  def get_rasterio_operations() -> Dict[str, List[str]]:
      """List available rasterio operations."""
      return {
          "operations": [
              "metadata_raster",
              "get_raster_crs",
              "clip_raster_with_shapefile",
              "resample_raster",
              "reproject_raster",
              "weighted_band_sum",
              "concat_bands",
              "raster_algebra",
              "compute_ndvi",
              "raster_histogram",
              "tile_raster",
              "raster_band_statistics",
              "extract_band",
              "zonal_statistics",
              "reclassify_raster",
              "focal_statistics",
              "hillshade",
              "write_raster"
          ]
      }

• src/gis_mcp/main.py:66-72 (registration)

  Imports the rasterio_functions module in the main entry point, which executes the decorators to register the 'raster_algebra' tool with the MCP server.

  from . import (
      geopandas_functions,
      shapely_functions,
      rasterio_functions,
      pyproj_functions,
      pysal_functions,
  )