i have several tif files, which some of them have No data values.

when Mosaic these files the ArcGIS replace the NoData value with black color RGB(0,0,0).

I want to keep the No data value in the Mosaiced result file

any Idea?


I don't know a way how to KEEP the NoData values. But you can REDEFINE the NoData value after adding your tif files to the mosaic dataset by using the toolbox data management => raster => mosaic dataset or using the python function DefineMosaicDatasetNoData_management. Please note that you probably need to recalculate your overviews, pyramids, etc afterwards.

  • Actually the problem if I defined the No data as RGB(0,0,0) i will loose some areas that actually they are RGB(0,0,0) – Ayman Salah Nov 22 '15 at 4:57

I don't know if you're still interested in a solution - I experienced the same problem and finally found what caused it:

  • You need to make sure that all the rasters you want to merge are set with the same pixel type and NoData Value respectively (you find this information under raster properties, see screenshot below).


If this is not the case, the Mosaic to new raster tool will use the NoData value of the "stronger" mosaic part (depending what operation you chose) for processing.

You can most easily change the pixel type and NoData parameters by using the copy raster function in your Data management-toolbox.


In the "Mosaic to New Raster" under "Pixel Type (optional)" make sure that the selected type covers the NoData values in the original files.

For example, assume that in the original raster files, NoData = -9999, if you select 8_BIT_UNSIGENED then all NoData values will be assigned 0 (which may be undesirable). However, if you select 32_BIT_FLOAT, all the NoData cells will be maintained correctly in the output file.

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