[GRASSLIST:5472] Text files, invalid points

[Lawrence Moran]

Hi,

thanks for you help with my PONET query- didn't manage to find source 
online, but found they convert (v.to.rst) with no problems.

I now need to produce a surface from a text file (sites). This is 
bathymetric data, so any positive value is erroneous. What is the best 
(easiest) way to find and remove such values, given that the file i too 
big to display in one go in spreadsheets such as excel?

Alternatively, is there a way to tell Grass to ignore these values when 
interpolating the surface?

Thanks,

Lawrence