Geospatial · Areas and surfaces

Spatial Interpolate

Estimates a smooth surface from measured sample points, on a hexagon or square grid. For example, a pollution surface from sensors.

Also known as: IDW, heat surface

How it works

Pick the Sample point geometry and the numeric Value column to interpolate. Grid is H3 hexes (lon/lat) by default with an H3 resolution of 7; Square grid (CRS units) needs a Cell size in the data's units. Each cell takes the inverse-distance-weighted average of the nearest samples: Power (IDW exponent) is 2, Neighbours per cell is 12, and Search radius limits how far a sample may be (metres on lon/lat data, CRS units otherwise; 0 means no limit). The output is one row per cell across the samples' extent, with the cell geometry, the estimated value in the Output column (interpolated by default) and sample_count. A cell with no sample in range gets NULL.

Inputs and outputs

Settings

{
  geometryColumn: string
  valueColumn: string
  grid: "h3"|"square"
  resolution: number (0-15, h3 only)
  cellSize: number (CRS units, square only)
  power: number (IDW exponent, default 2)
  maxNeighbors: number (1-100)
  searchRadius: number (metres on a lon/lat CRS, else CRS units; 0 = no limit)
  outputColumn: string
}

Example

You have 40 air-quality sensors and want a surface for the whole city. Set Value column to pm25, keep H3 hexes at resolution 8, set Search radius to 3000 so a cell far from every sensor stays NULL rather than guessing, and name the Output column pm25_est. A Map node then draws the hexagons as a choropleth.

More in Areas and surfaces

• Trade Areas — Builds catchment areas around each location: distance rings, drive-time bands, areas traced from demand, or rings cut into sectors.
• Gravity Model — Splits each area's demand between the locations in range by their attractiveness and distance (the Huff model). Gives the demand each location captures, such as a new store's sales and what it takes from the others, the top location per area, or a probability for every area and location.
• Calibrate Gravity Model — Fits the Gravity Model's attractiveness and distance-decay settings to what customers actually did, such as loyalty-card visits per area and store, and reports how well the fit reproduces each store.
• Voronoi — Draws one area per point covering everywhere closer to it than to any other point, such as the nearest-store territory for every shop.
• H3 Aggregate — Puts features into hexagon cells of a chosen size and summarizes each cell, for an even grid on density maps.