# Use of NaN

From Interactive System for Ice sheet Simulation

Fields possibly using NaN:

- Via stag/unstag:
- btrc/beta
- NaN test @ glam_strs2.F90:2845
- NaN test @ ice3d_lib.F90:1430

- uvel/vvel
- kinematic_bc_[uv]
- Nan where
**not**GLIDE_IS_DIRICHLET_BOUNDARY(geometry_mask) - Only used by ice3d_lib.F90:927

- Nan where
- ice3d_lib.F90:720
- disabled code sets all ice-free points to nan to test if ice-free points are being used in calculations incorrectly

- kinematic_bc_[uv]

- btrc/beta
- marine_bc_normal: "NaN for all points except those that occur on the marine margin of an ice shelf, in which case contains the angle of the normal to the ice front."
- NaN precisely where
**not**GLIDE_IS_CALVING(mask(i,j)) - ice3d_lib.F90 - OK
- becomes latbc_normal in sparuv()
- becomes normals in sparse_marine_margin() called only when GLIDE_IS_CALVING(mask(i,j)) so no problem here

- glam_strs2.F90 - OK
- Seems to calculate the normals on its own in getlatboundinfo()

- NaN precisely where