ee 
satellite navigation as a possible system for adequate naviga- 
tional control for Ocean Surveys. The development of both of 
these systems will be followed closely. 
Until these systems are operational, Ocean Survey ships 
will depend for position control. primarily on Loran-C with 
back-up by such conventional systems as Loran-A, the sextant, 
and dead-reckoning. 
G. Types of Investigation 
Investigations are categorized by the spacing of ships' 
tracklines and the frequency of data collection. Four basic 
types are included in the Ocean Surveys Plan: exploratory, 
developmental, time-series, and synoptic. These surveys are 
also divided according to the method of ship operation into 
underway operations and oceanographic station operations. 
Exploratory surveys are those conducted to develop the 
gross features and general conditions in an area where little 
data are available. 
Developmental surveys are those conducted to determine 
the detailed features and environmental conditions in an area 
where enough previous data exist to plan such a survey 
intelligently. 
Time-seriles surveys are those in which a ship or an 
instrumented buoy remains in one place making repeated obser- 
vations of those factors that vary with time. 
Synoptic surveys are those that obtain simultaneous 
observations and measurements of the time-dependent variables 
