AST.ZERO_ACCUM

Prevents unstable SNR masks halting convergence

Description:

Masks defined by SNR limits can show instabilities in which pixels can repeatedly enter the mask on one iteration and leave it on the next. Such oscillating pixels tend to occur around the edges of source areas in the mask, and can prevent convergence of the iterative map-making process. Setting AST.ZERO_ACCUM to a non-zero value can prevent this by forcing source pixels to be accumulated rather than replaced on successive iterations. Thus, if AST.ZERO_ACCUM is non-zero, any map pixel which is flagged as a source pixel on some iteration will never be unflagged - once a source pixel, always a souce pixel. [0]
Type:
integer

SMURF Usage

MAKEMAP, CALCQU