How to mark some points on 2D heat map in gnuplot?

Question

I am using simple scheme for plot 2D heat map from my data like this:

set pm3d map
set pm3d interpolation 5,5
splot \"file\"

Now i need to

Answer 1

What does the file look like? You can do:

splot 'file' with pm3d, 'points' with points linecolor rgb "white"

depending on what 'points' looks like though, you might need to add a using specification:

splot 'file' with pm3d, 'points' using 1:2:(0.0) with points linecolor rgb "white"