Consider this part of the script:
FOR %%G IN (Eqr_360_????.jpg) DO ( ffmpeg -f lavfi -i nullsrc=size=3888x3888 -vf format=pix_fmts=gray16le,geq=Y-^(20*^(Y/1939^)*^(3887-X^)/3887^)*gt(Y,1880) -frames 1 -y %FF%YmapCenter.pgm ) pause
Adding "" around this line does not get the script to work. Went for the alternate to then added ^ to protect the parentheses ( ) but gt() could not be protected.
Using "" about the line or using ^ to protect the parentheses () always returns the error ... Unknown function gt(Y,1880
Removing the *gt(Y,1880) allows the script to work.
In a second attempt I removed the CMD FOR statement and set the file name directly. This means there is no command shell conflict, but the error message persists ... Unknown function gt(Y,1880