RasterVectorJoin

The RasterVectorJoin operator allows combining a single vector input and multiple raster inputs. For each raster input, a new column is added to the collection from the vector input. The new column contains the value of the raster at the location of the vector feature. For features covering multiple pixels like MultiPoints or MultiPolygons, the value is calculated using an aggregation function selected by the user. The same is true if the temporal extent of a vector feature covers multiple raster time steps. More details are described below.

Example: You have a collection of agricultural fields (Polygons) and a collection of raster images containing each pixel's monthly NDVI value. For your application, you want to know the NDVI value of each field. The RasterVectorJoin operator allows you to combine the vector and raster data and offers multiple spatial and temporal aggregation strategies. For example, you can use the first aggregation function to get the NDVI value of the first pixel that intersects with each field. This is useful for exploratory analysis since the computation is very fast. To calculate the mean NDVI value of all pixels that intersect with the field you should use the mean aggregation function. Since the NDVI data is a monthly time series, you have to specify the temporal aggregation function as well. The default is none which will create a new feature for each month. Other options are first and mean which will calculate the first or mean NDVI value for each field over time.

Inputs

The RasterVectorJoin operator expects one vector input and one or more raster inputs.

Parameter	Type
`sources`	`SingleVectorMultipleRasterSources`

Parameters

The RasterVectorJoin operator has the following parameters:

Parameter	Type	Description	Example Value
`names`	`ColumnNames`	Specify how the new column names are derived from the raster band names.	"{"type": "default}"
`featureAggregation`	`first` or `mean`	The aggregation function to use for features covering multiple pixels.	"first"
`featureAggregationIgnoreNoData`	(optional) `boolean`	Whether to ignore no data values in the aggregation. Defaults to `false`	false
`temporalAggregation`	`none`, `first` or `mean`	The aggregation function to use for features covering multiple (raster) time steps.	"none"
`temporalAggregationIgnoreNoData`	(optional) `boolean`	Whether to ignore no data values in the aggregation. Defaults to `false`	false

Types

ColumnNames

The ColumnNames type is used to specify how the new column names are derived from the raster band names.

Value	Description
`{"type": "default"}`	Appends " (n)" to the band name with the smallest `n` that avoids a conflict
`{"type": "suffix", "values": [string]}`	Specifies a suffix for each input, to be appended to the band names
`{"type": "rename", "values": [string]}`	A list of names for each new column

Errors

If the length of names is not equal to the number of raster inputs, an error is thrown.

Example JSON

{
  "type": "RasterVectorJoin",
  "params": {
    "names": ["NDVI"],
    "featureAggregation": "first",
    "temporalAggregation": "mean",
    "temporalAggregationIgnoreNoData": true
  },
  "sources": {
    "vector": {
      "type": "OgrSource",
      "params": {
        "data": "places"
      }
    },
    "rasters": [
      {
        "type": "GdalSource",
        "params": {
          "data": "ndvi"
        }
      }
    ]
  }
}