Morphological Urban Footprint Extraction (Phoenix)

# Platform Comparison: Morphological Urban Extraction — Gold Spec
#
# Extract urban footprint from ESA WorldCover 2021 over Phoenix metro
# using morphological filtering.  Ground truth: ~58% urban.
#
# This spec is designed to run through both the Python backend and
# browser-wasm executor (folia bench exec -b browser-wasm).

name: morphological-urban
version: "1.0"
description: >
  Extract the urban footprint from ESA WorldCover 2021 (10m) over the
  Phoenix metro area.  Threshold built-up pixels (class 50), apply
  morphological opening (radius=2) then closing (radius=3), and report
  the percentage of the AOI classified as urban.
  Ground truth: ~58% (calibrated from GEE 2026-03-29).

settings:
  default_bbox: [-112.2, 33.3, -111.8, 33.6]
  default_crs: EPSG:4326

layers:

  # ============================================================
  # SOURCE LAYERS
  # ============================================================

  source/worldcover:
    uri: stac://earth-search/esa-worldcover
    type: raster
    description: >
      ESA WorldCover 2021 (10m).  Class 50 = built-up.
    params:
      bbox: [-112.2, 33.3, -111.8, 33.6]

  # ============================================================
  # COMPUTE: URBAN EXTRACTION PIPELINE
  # ============================================================

  compute/urban-threshold:
    type: raster
    description: >
      Binary mask of built-up pixels (WorldCover class 50 = 1, else 0).
    compute:
      op: raster_threshold_mask
      inputs:
        data: { layer: source/worldcover }
      params:
        threshold: 50
        operator: eq

  compute/opened:
    type: raster
    description: >
      Morphological opening (erode then dilate) with radius=2.
      Removes isolated built-up pixels smaller than the kernel.
    compute:
      op: morph_open
      inputs:
        data: { layer: compute/urban-threshold }
      params:
        radius: 2

  compute/urban-footprint:
    type: raster
    description: >
      Morphological closing (dilate then erode) with radius=3.
      Fills small gaps in the urban fabric.
    compute:
      op: morph_close
      inputs:
        data: { layer: compute/opened }
      params:
        radius: 3

  # ============================================================
  # RESULT: URBAN PERCENTAGE
  # ============================================================

  result/urban-pct:
    type: table
    description: >
      Percentage of the AOI classified as urban after morphological cleanup.
      Ground truth: ~58%.
    compute:
      op: analysis_zonal_stats
      params:
        stats: [mean]
      inputs:
        raster: { layer: compute/urban-footprint }