MARPLOT BINARY LAYER FILE FORMAT:  SUM (summary) files

offset (long) //byte index of start of object in OBJ file (negative ->
              //object is deleted)
low-long + 180000000 (long)   	<-
low-lat + 90000000  (long)	<- all 0 for
hi-long + 180000000 (long)	<- alias objects
hi-lat + 90000000 (long)	<-
id (8 bytes)
first four characters of object's name (null terminated if < 4 chars) (4 bytes)
< repeat for number of objects >