The package uses a special arc line information database to optimise its search algorithm. This algorithm requires sets of about 12 lines with which to work. The database consists of lines and their 10 nearest neighbours on each side (left and right).
The arc line list supplied (.ARC file) does not contain sufficient lines for the database to be useful. Either more lines must be added to the list, or another program (such as ECHARC) must be used for the line identification phase. It is permissible to add dummy entries to the line list just to overcome this limitation, however, in this case it is unlikely that automatic identification will work and the program will probably need to be run interactively.
Martin Clayton