Rasterization

The Rasterization operator creates a raster from a point vector source. It offers two options for rasterization: A grid rasterization and a (gaussian) density rasterization (heatmap).

Inputs

The Rasterization operator expects exactly one vector input.

ParameterType
sourceSingleVectorSource

Parameters

ParameterTypeDescriptionExample Value
paramsGridOrDensityThe type and parameters for the rasterization to perform.{"type": "grid", ...}

GridOrDensity contains a field type which can have the value grid or density for a grid rasterization or density rasterization, respectively.

GridOrDensity has additional fields which are parameters specific to the type of the rasterization. These are described below separately.

Grid Rasterization

ParameterTypeDescriptionExample Value
spatialResolutionSpatialResolutionThe spatial resolution of the grid/size of the grid cells.{"x": 10.0, "y": 10.0}
originCoordinateCoordinate2DThe origin coordinate to which the grid is aligned.{"x": 0.0, "y": 0.0}
gridSizeModefixed or relativeThe mode how the grid resolution is interpreted."fixed"

Types

The following describes the types used in the grid rasterization parameters.

The parameters spatialResolution and originCoordinate consist of two fields x and y which describe a resolution/position in x/y direction.

For gridSizeMode the two options fixed and relative are available. Fixed means the spatialResolution is interpreted as a constant grid cell size. Relative means the spatialResolution is used as a multiplier for a query's spatial resolution, making the resulting grid size adaptive to the query resolution.

Density Rasterization

ParameterTypeDescriptionExample Value
cutoffnumberDefines the cutoff (as percentage of maximum density) down to which a point is taken into account for an output pixel density value0.01
stddevnumberThe standard deviation parameter for the gaussian function.1.0

The cutoff percentage (must be in [0, 1)) is treated as a hard cutoff point. A larger cutoff percentage leads to faster processing, however it also introduces inaccuracies in the result since points further than the derived radius away from a pixel do not influence its value. It is meant to be set such that the ignored density values are small enough to not make a visible difference in the resulting raster.

Errors

If the cutoff is not in [0, 1) or the stddev is negative, an error will be thrown.

Example JSON

Grid Rasterization

{
  "type": "Raster",
  "operator": {
    "type": "Rasterization",
    "params": {
      "type": "grid",
      "spatialResolution": {
        "x": 10,
        "y": 10
      },
      "gridSizeMode": "fixed",
      "originCoordinate": {
        "x": 0, 
        "y": 0
      }
    },
    "sources": {
      "vector": {
        "type": "OgrSource",
        "params": {
          "data": "ne_10m_ports",
          "attributeProjection": null,
          "attributeFilters": null
        }
      }
    }
  }
}

Density Rasterization

{
  "type": "Raster",
  "operator": {
    "type": "Rasterization",
    "params": {
      "type": "density",
      "cutoff": 0.01,
      "stddev": 1
    },
    "sources": {
      "vector": {
        "type": "OgrSource",
        "params": {
          "data": "ne_10m_ports",
          "attributeProjection": null,
          "attributeFilters": null
        }
      }
    }
  }
}