1 degree ocean mask

[Ben Burford]

Hello,

I want to apply a mask over the ocean for my 1 degree by 1 degree global
gridded data.  I think I can simply do the following:
d maskout(data,land(t=1)-1)
where land is a mask data file with 1 over land and 0 over ocean.

Does anyone know where I can find a 1 degree by 1 degree global gridded
land/ocean mask file?

As I understand it basemap.gs will do masking of graphics, but not of the
the data, and I want to mask the data during calculations.

Thank you very much,

Ben