I have two Images which overlap and I want to mosaic the two images. One of the images has nodata values in this overlapping area and the other does not. I obviously want the overlapping area to be image data and not nodata values but how do I define which data gets written to the output file? In ArcGIS one can set either match, last or first. But I don´t see a similar option with FME2014.

1 Answer 1


The order of the input features determines the order in which rasters will be drawn. The first raster to enter will be drawn first, then each subsequent raster will be drawn on top of any previous overlapping rasters.

In this case the nodata raster should be first. You can use a Sorter transformer to enforce the order in which the features are processed, or change the order of the Readers in the Navigator window.

  • Just came across this answer and wanted to add that there is an update in FME2017 where you can get to choose the order of overlap in the Mosaicker transformer itself. You can choose to take the first cell, or the last cell, or the minimum, maximum, average, or sum of all cells. Feb 10, 2017 at 20:50

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