Change default value of step and `step_deg`

A negative value is even more striking since a step for a uniform grid
would be positive.

Inst_eddies/input_ssh.f90

@@ -5,7 +5,7 @@ module input_ssh_m
   real, protected:: corner_whole(2) = huge(0.)
   ! longitude and latitude of the corner of the whole grid, in rad
 
-  real, protected:: step(2) = huge(0.) ! longitude and latitude steps, in rad
+  real, protected:: step(2) = - huge(0.) ! longitude and latitude steps, in rad
 
   integer, protected:: nlon = - huge(0), nlat = - huge(0)
   ! size of ssh array in input NetCDF, assuming no repeated point if
@@ -83,7 +83,7 @@ contains
     ! point corresponding to u(1, 1) or v(1, 1) respective to point
     ! corresponding to ssh(1, 1).
 
-    real:: step_deg(2) = huge(0.) ! longitude and latitude steps, in degrees
+    real:: step_deg(2) = - huge(0.) ! longitude and latitude steps, in degrees
     real lon_max, lat_max ! longitude and latitude, in degrees
     integer copy
     namelist /grid_nml/ corner_deg, step_deg, nlon, nlat, periodic, &