Weighted Overlay - Solar Siting

Persona: Renewable energy analyst, land use planner Concept: #terrain, #land-coverDifficulty: Advanced

Scenario

Identify suitable sites for solar energy development in southern Utah using multi-criteria analysis. Combine terrain suitability (slope, aspect, TPI), land cover classification, protected area exclusions, and grid proximity into a weighted composite score. Aggregate results onto an H3 hexagonal grid for standardized comparison.

Data Sources

Layer	Source	Type	Resolution
DEM	USGS 3DEP	raster	10m
Land cover	NLCD 2021	raster	30m
Protected areas	PAD-US	vector	N/A
Transmission lines	HIFLD	vector	N/A

Operations Used

Operation	Purpose
terrain_slope	Derive slope (flat terrain preferred)
terrain_aspect	Derive aspect (south-facing preferred)
terrain_tpi	Derive topographic position (flat/plateau preferred)
raster_reclassify	Score each criterion into 0-1 suitability
vector_buffer	Create 500m exclusion zones around protected areas
analysis_distance_to_features	Distance to transmission lines
raster_normalize	Invert distance to proximity score
analysis_weighted_overlay	Combine criteria with configurable weights
analysis_h3_index	Aggregate to H3 hexagonal grid

Pipeline Structure

source/dem ──┬── terrain/slope ──── analysis/slope-suitability ──┐
             ├── terrain/aspect ─── analysis/aspect-suitability ──┤
             └── terrain/tpi ────── analysis/tpi-suitability ─────┤
source/landcover ───────────────── analysis/land-suitability ─────┤
source/protected-areas ─────────── analysis/exclusion-zones       │
source/transmission-lines ──┐                                     │
source/dem ─────────────────┴── analysis/grid-distance ───────────┤
                                analysis/grid-proximity ──────────┤
                                                                  ▼
                                               suitability/composite
                                                        │
                                               suitability/site-hexes

Complete Workspace

name: solar-siting-utah
version: "1.0"
description: >
  Multi-criteria solar siting analysis for southern Utah.
  Combines terrain, land cover, protected areas, and grid proximity
  into a weighted suitability surface with H3 hex aggregation.

settings:
  default_bbox: [-113.5, 38.1, -113.0, 38.6]
  default_crs: EPSG:32612

layers:

  # --- SOURCE DATA ---

  source/dem:
    uri: data/dem.tif
    type: raster
    description: USGS 3DEP 10m DEM
    geo:
      bbox: [-113.5, 38.1, -113.0, 38.6]

  source/landcover:
    uri: data/nlcd.tif
    type: raster
    description: NLCD 2021 land cover (30m)

  source/protected-areas:
    uri: data/protected_areas.geojson
    type: vector
    description: PAD-US protected areas

  source/transmission-lines:
    uri: data/transmission_lines.geojson
    type: vector
    description: HIFLD electric transmission lines

  # --- TERRAIN ---

  terrain/slope:
    type: raster
    compute:
      op: terrain_slope
      inputs:
        dem: { layer: source/dem }

  terrain/aspect:
    type: raster
    compute:
      op: terrain_aspect
      inputs:
        dem: { layer: source/dem }

  terrain/tpi:
    type: raster
    compute:
      op: terrain_tpi
      inputs:
        dem: { layer: source/dem }
      params:
        radius: 3

  # --- SUITABILITY SCORING ---

  analysis/slope-suitability:
    type: raster
    description: "0-5° ideal (1.0), 5-10° good (0.75), 10-15° marginal (0.5), >15° exclude (0.0)"
    compute:
      op: raster_reclassify
      inputs:
        raster: { layer: terrain/slope }
      params:
        method: manual
        breaks: [5, 10, 15]
        class_values: [1.0, 0.75, 0.5, 0.0]

  analysis/aspect-suitability:
    type: raster
    description: "South-facing (135-225°) ideal, E/W marginal, N poor"
    compute:
      op: raster_reclassify
      inputs:
        raster: { layer: terrain/aspect }
      params:
        method: manual
        breaks: [90, 135, 225, 270]
        class_values: [0.0, 0.5, 1.0, 0.5, 0.0]

  analysis/land-suitability:
    type: raster
    description: "NLCD class scored for solar: grassland=5, shrub=4, barren=4, forest=1, developed=0"
    compute:
      op: raster_reclassify
      inputs:
        raster: { layer: source/landcover }
      params:
        method: value_map
        value_map:
          "71": 5.0    # Grassland - ideal
          "52": 4.0    # Shrub/Scrub - good
          "31": 4.0    # Barren Land - good
          "81": 3.0    # Pasture - acceptable
          "82": 3.0    # Cropland - acceptable
          "41": 1.0    # Forest - poor
          "42": 1.0    # Evergreen - poor
          "11": 0.0    # Water - exclude
          "21": 0.0    # Developed - exclude

  analysis/exclusion-zones:
    type: vector
    description: "500m buffer around protected areas - hard exclusion"
    compute:
      op: vector_buffer
      inputs:
        features: { layer: source/protected-areas }
      params:
        distance: 500

  analysis/grid-distance:
    type: raster
    compute:
      op: analysis_distance_to_features
      inputs:
        raster: { layer: source/dem }
        features: { layer: source/transmission-lines }

  analysis/grid-proximity:
    type: raster
    description: "Inverted distance: closer to grid = higher score"
    compute:
      op: raster_normalize
      inputs:
        raster: { layer: analysis/grid-distance }
      params:
        method: minmax
        output_range: [1.0, 0.0]

  # --- COMPOSITE ---

  suitability/composite:
    type: raster
    description: Weighted multi-criteria suitability (0-1)
    compute:
      op: analysis_weighted_overlay
      inputs:
        rasters:
          - { layer: analysis/slope-suitability }
          - { layer: analysis/aspect-suitability }
          - { layer: analysis/land-suitability }
          - { layer: analysis/grid-proximity }
      params:
        weights: [0.30, 0.20, 0.25, 0.25]
        normalize_inputs: true
    style:
      colorRamp:
        - { value: 0.0, color: "#d73027" }
        - { value: 0.25, color: "#fc8d59" }
        - { value: 0.5, color: "#fee08b" }
        - { value: 0.75, color: "#91cf60" }
        - { value: 1.0, color: "#1a9850" }
      info:
        fields: [value]
        format: "Suitability: {value:.0%}"
      form:
        fields:
          - name: slope_weight
            type: slider
            min: 0
            max: 1
            step: 0.05
            default: 0.30
            label: Slope Weight
          - name: aspect_weight
            type: slider
            min: 0
            max: 1
            step: 0.05
            default: 0.20
            label: Aspect Weight
          - name: land_weight
            type: slider
            min: 0
            max: 1
            step: 0.05
            default: 0.25
            label: Land Cover Weight
          - name: grid_weight
            type: slider
            min: 0
            max: 1
            step: 0.05
            default: 0.25
            label: Grid Proximity Weight

  # --- H3 AGGREGATION ---

  suitability/site-hexes:
    type: vector
    description: H3 hex grid aggregation of suitability scores
    compute:
      op: analysis_h3_index
      inputs:
        raster: { layer: suitability/composite }
      params:
        resolution: 7
        stats: [mean, min, max]
    style:
      fill-opacity: 0.6
      table:
        columns:
          - { field: h3_cell_id, label: "Hex Cell" }
          - { field: mean, label: "Mean Score", format: ".2f" }
          - { field: min, label: "Min Score", format: ".2f" }
          - { field: max, label: "Max Score", format: ".2f" }

Interactive Weights

The form: block on suitability/composite exposes weight sliders. Adjusting a slider triggers recomputation of the weighted overlay with new weights. This is direct manipulation: dragging a slider beats typing a threshold.

The form controls bind to compute.params.weights via parameter names. The UI normalizes weights to sum to 1 before recomputing.