This Fortran function generates a new field from an existing field by interpolation.
Before invoking this function, the new field must be described by suitable calls to INTOUT. If the original field is not in GRIB format, a definition for it must be provided by suitable calls to INTIN.
Declare the function as INTEGER and EXTERNAL, and invoke it as follows:
IRET = INTF(INGRIB,INLEN,FLDIN,OUTGRIB,OUTLEN,FLDOUT)
It is important to check the return value in IRET to ensure the call has been successful.
In the special case when the specification for the output field is identical to that of the input field, interpolation is not carried out. This is an important optimisation for MARS processing and is indicated by a combination of return values in IRET and OUTLEN (both are set to zero).
All six parameters must be given in the function call even though only four have significance in a given call.
Return value.
The return value, IRET, is 0 if the call is successful.
In the special case when the specification for the output field is identical to that of the input field, interpolation is not carried out. This case is indicated on return by:
- IRET = 0
- OUTLEN = 0
- OUTGRIB (or FLDOUT) does not contain the `new' field since it already exists in INGRIB (or FLDIN).