Select First Value

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Summary: This process accepts multiple coverage inputs and selects data from the first non-null input. Input coverages must have identical coverage definitions.


  • Input Coverage (0 or more Coverage) One of the coverages from which to select data.

Output: Coverage

  • Description: A coverage made up of the first non-null values from the combined Input Coverages.

Attributes: This process has no attributes.


When you connect an Input Coverage to the process, the process automatically generates a new empty input to accept another coverage. For a given cell to be rendered, if the first (topmost) Input Coverage has data for that cell, that data will be used. If the first Input Coverage does not have data for the cell then data from the second Input Coverage will be used. If the second Input Coverage does not have data for the cell then data from the third Input Coverage will be used, and so on.

It is possible that no input will have data for a given cell, in which case nothing will be rendered for that cell.

It is possible to use this process with 0 or 1 inputs, but rather pointless.


Consider two datasets each with an associated pipeline. One dataset contains low resolution image data for an area of the globe, the second data set contains high resolution imagery for the same area of the globe, but does not have imagery for the entire area. Connecting the output of the high resolution dataset to the first input of this process and the output of the low resolution dataset to the second input will cause high resolution imagery to be rendered if it is available. Where high resolution imagery within the area is not available, the low resolution imagery will be rendered instead.

If neither dataset has imagery for a portion of the area, then nothing will be rendered for that portion.

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