I have several Australia-wide GeoTIFF with 3 bands x, y and z and there appears to be no way in M9 to export to an ascii grid such as .asc

No luck in R "terra" either because AAIG driver doesn't support 3 bands.

All I can think of is exporting to xyz and interpolating. Ideas?

Aussie Nature Shots

there appears to be no way in M9 to export to an ascii grid such as .asc

What specific format did you have in mind? What program will be consuming the data you want to export?

The ubiquitous format for raster ASCII grids in GIS is Esri ASCII grid format, which uses three letter extensions .grd or .asc. Esri ASCII grid only supports rasters with a single numeric band, so when 9 writes an ASCII grid file it does that for a single band. I suppose that's also why R and GDAL also write only a single band to Esri ASCII grid format.

The way Esri implements multiple bands is by having multiple files, not multiple bands in a single file. I don't know if that can be done in Esri products with the ASCII form of grid files, as opposed to their binary form.

This is for species distribution/habitat suitability modelling where environmental variables are input as .asc

Solved, the three channels misled me.

M9 Transform Filter, Tile, Channel 2, Filter maximum, Shape square, Radius 1

New Image and Table export to .asc

Aussie Nature Shots