Posting here for posterity.
So the RAS suite used by rAM3 still contains old ancillary tasks that use the FORTRAN-based ‘CAP’ workflow.
These have been replaced in the newer AM3-CCI ancillary suite created by @lachlanswhyborn and @ben which is purely python/ants based.
However, if you fail to define your binary-land sea mask as an integer (and keep it as a float), old RAS tasks such as ancil_cap_vegfrac will fail with outputs such as:
SPIRAL SEARCH RADIUS SET TO 1000
Reading target land sea mask 0
Attempting to open file
/home/548/pag548/cylc-run/rCM3-ancil-suite/share/data/ancils/Lismore/d1100/qrpa
rm.mask
No. of land points 0
...
Calculating bi-linear interpolation coeffs
Finding coastal points
Setting coastal values
WARNING - No source data is available in target domain
Interpolating MODIS data to target grid
A total of 0 points are to be set
...
Finding coastal points
Setting coastal values
WARNING - No source data is available in target domain
Calculating grid cell MODIS LAIs
Imposing land sea mask on fractions of IGBP classes
Dealing with land ice. Threshold = 1.10000000000000
Searching for unresolved points in IGBP summations
No unresolved points found
DIAGNOSTIC LAND SEA MASK FOR IGBP VEG FRACTIONS
ALPHA CHARACTERS DENOTE POINTS THAT WERE UNRESOLVED
A=1, B=2, C=3 etc grid length searches required
LAND SEA MASK FOR ROWS 1 TO 50AND FOR POINTS 1 TO 50
*********************00000000000000000000000000000
**********************0000000000000000000000000000
**********************0000000000000000000000000000
**********************0000000000000000000000000000
**********************0000000000000000000000000000
**********************0000000000000000000000000000
Whereas if you set the land-binary mask as an integer, you will get
SPIRAL SEARCH RADIUS SET TO 1000
Reading target land sea mask 0
Attempting to open file
/home/548/pag548/cylc-run/rCM3-ancil-suite/share/data/ancils/Lismore/d1100/qrpa
rm.mask
No. of land points 1159
...
Calculating bi-linear interpolation coeffs
Finding coastal points
Setting coastal values
A total of 1159 points are to be set
...
Finding coastal points
Setting coastal values
Calculating grid cell MODIS LAIs
Imposing land sea mask on fractions of IGBP classes
Dealing with land ice. Threshold = 1.10000000000000
Searching for unresolved points in IGBP summations
No unresolved points found
DIAGNOSTIC LAND SEA MASK FOR IGBP VEG FRACTIONS
ALPHA CHARACTERS DENOTE POINTS THAT WERE UNRESOLVED
A=1, B=2, C=3 etc grid length searches required
LAND SEA MASK FOR ROWS 1 TO 50AND FOR POINTS 1 TO 50
11111111111111111111100000000000000000000000000000
11111111111111111111110000000000000000000000000000
11111111111111111111110000000000000000000000000000
11111111111111111111110000000000000000000000000000
11111111111111111111110000000000000000000000000000