Hi, I'm to find ways to import a spatial interpolated grid created using IDW method in MapInfo (saved under .MIF and .MIDI formats) into an ArcGIS online web map? I gather I might have to rerun the grid calculations in QGIS and then save as a GEOTIFF file. And then upload to ArcGIS Pro and create a tile service to save to ArcGIS online?
This will be an out of the box idea but, depending how the size of the raster, you could also consider using a Media Layer. This probably isn't the way ESRI was intending to use these layers but your could- export your grid as a JPG or PNG and follow the instructions for adding it to your map. It's one way of adding raster content that might make sense for pure visual purposes over a small area (Media Layers have to be less than 10mb in size)..