How to merge raster with FME with different spatial resulution?

Question

I have two sets of raster (tiff, aerial photos) which I want to merge to one raster file with FME. The two sets have different spatial resolutions. Set A has a better resolution as B. The two set do overlap. How can I merge these raster with FME? Requirements:

1. Use Resolution (size of pixel) from set A
2. Where the raster do overlap: use pixels from set A
3. Optional requirement: Position of pixels from set A should not change (nor resampling of A. only resampling of B)

Example with 4 raster files from set A (blue) and 4 raster files from set B (red).

I tried to use FMEs RasterMosaiker and set the order in Navigator but I can not meet requirement 1 and 2 simultaneously:

• first A then B: I loss requirement 2
• first B then A: I loss requirement 1

Answer 1

I don't do a lot of raster work with FME so this might not be entirely correct, but these are the general steps I would use:

1. Use a RasterResampler to change the Cell Sizing of Raster B. You could extract this from Raster A first and feed it into the X/Y spacing. Or, just type it in manually if you know it.

   

2. Feed the results of the above along with Raster A into a RasterMosaicker.

3. You could also have a look at the RasterExpressionEvaluator which can do conditional statements where the two rasters overlap.