The input file must be in the benchmark file format used in the NAVD 88 adjustment. (Files in this format were often named file.bms) The relevant fields in this text file are as follows:
cc 50-51 latitude degrees (integer) cc 52-53 latitude minutes (integer) cc 54-55 latitude seconds (integer only - no decimal point) cc 57-59 longitude degrees (integer) cc 60-61 longitude minutes (integer) cc 62-63 longitude seconds (integer) cc 76-83 gravity (in gals) cc 84-88 estimated standard deviation (in milligals)
If the gravity field in the input record is populated (more specifically, if cc 76 contains the character "9"), then the entire input record is written to the output with no change. If cc 76 of the input record contains any other character, then gravity and its standard deviation are computed as a function of the given latitude and longitude, inserted into the record, and the entire record is written to out put. This means that any information in cc 1-49 is written to output with no change.