3 = NGS Blue Book Format : 

 NGS Horizontal (Vol 1) Blue Book format - *80* (Control Point) and *86* (Combo Height) Records.
INTG uses information from the *80* and *86* records in Blue Book files. 
The Station Serial Number(SSN), and the Latitude and the Longitude
are read from the *80* records.  
The rest of the record is ignored. 
Only the *86* record is modified by INTG - The *80* records and all other records are passed through without change to the output file.
Any *84* records are deleted.
Information in cols 36-43 in the *86* record is created by INTG.

For more information on this format, please refer to: 
   'Input Formats and Specifications of the National Geodetic Survey Data Base' 
   'Volume 1. Horizontal Control Data'. 
Published by the Federal Geodetic Control Committee in September 1994 and 
available from: the National Geodetic Survey, NOAA,  Silver Spring, MD 20910. 

 The following input example is *80* and *86* records from a Blue Book file: 

004560*80*0096KNOXVILLE CT HSE              411906578  N0930548534  W 277  MIA33
004565*86*0096 any geoid values in here     will be overwritten if ssn matches